03-01-2011 At 04:00:00 PM
Speaker: Dr.Sairam Tangirala, Center for Simulational Physics,University of Georgia, Athens, USA
Category: CMP Seminar
Venue: Lecture Hall
Morphological scaling properties of linear polymer films grown by vapor deposition polymerization (VDP) using 1+1D Monte Carlosimulations will be discussed in this talk. The lattice model implements the basicprocesses of random angle ballistic deposition (F), free-monomer diffusion (D), and monomer adsorption along with other dynamical processes of polymer chaininitiation,extension, and merger. The ratio G=D/F is found to have a strong influence on the polymer film morphology. Spatial and temporal behavior of kinetic roughening has been extensively studied using finite-length scaling and height-heightcorrelations. The scaling analysis has been performed within no-overhangapproximation andrelevant scaling exponents for film-interface evolution have been studied forvarying free-monomer diffusion.
07-01-2011 At 04:00:00 PM
Speaker: Mr. Santosh Kumar Das, VECC, Kolkata
Category: NP Seminar
Venue: Lecture Hall
10-01-2011 At 04:00:00 PM
Speaker: Prof. S. Nozaki, University of Electro-Communications, Tokyo, Japan
Category: Biresh Patel Memorial Lecture 2011
Venue: Lecture Hall
The ultimate goal of nanofabrication is to control the size and positioning. We propose a simple and innovative way to achieve the goal by making the best use of a strong photon-nanoparticle interaction. Because of its large surface to volume ratio and carrier confinement in a nanoparticle, the semiconductor nanoparticle can be easily modified or synthesized by the light irradiation. We have observed two unique phenomena to manifest the photon-nanoparticle interaction: photo-oxidation and photo-synthesis. In both photo-oxidation and photo-synthesis, the sizes are self-limited to the photon energy of monochromatic light such as laser and are well controlled.
12-01-2011 At 04:00:00 PM
Speaker: Prof,. Amitabhy Vaimani, Brussels University, Belgium
Category: Colloquium
Venue: Lecture Hall
Black holes are our best guide towards understandingproperties of a quantum theory of gravity. On one hand, the study ofblack holes has revolutionized our understanding of string theory as awhole, and on the other hand string theory has come a long way inaddressing puzzles associated with black holes. In this talk I willprovide an overview of these exciting developments. I will discussthat a lot more can be learned about black holes using the hiddensymmetries of string/supergravity theories. I will conclude with somerecent ideas about the microscopic understanding of rotating extremalblack holes.
12-01-2011 At 11:00:00 AM
Speaker: Prof. P. Ring, Physics Department, Technical University of Munich, 85748 Garching, Germany}
Category: General Seminar
Venue: Lecture Hall
Investigations of nuclei far from stability are presently at the forefront of nuclear science. Density functional theory (DFT) is an important tool for a universal description of medium heavy and heavy systems. Because of the consistent treatment of spin degrees of freedom static and dynamic versions of covariant density functional Theory (CDFT) provide a very successful description of nuclear properties all over the periodic table. Excited states are treated in time dependent density functional theory (TDDFT) which is treated in different approximations:a) On the mean field level the relativistic quasiparticle random phase approximation (RQRPA) is used to investigate the multipole response in spherical and deformed nuclei far from stability, in particular low-lying modes [1], giant resonances [2], spin-isospin modes, scissor modes [3] and new exotic resonances, such as pygmy [4] or toroidal modes.b) Going beyond the mean field approximation, an energy dependent self-energy is constructed by coupling of the single particle motion to low-lying surface modes. This leads to an enhanced level density at the Fermi surface and an induced interaction in the resulting Bethe-Salpeter equation, which is solved in the time blocking approximation (TBA) [5]. No additional parameters are used and double counting is avoided by a proper subtraction method. This method is applied in several isotopic chains of spherical nuclei for the investigation of the width of giant resonances and of the coupling of low-lying dipole excitations to complex configurations [6].c) In transitional nuclei a theory is developed which uses the relativistic generator coordinate method (RGCM) as a basis to perform configuration mixing calculations of angular momentum and particle number projected wave functions [7] and to derive a collective hamiltonian in five quadrupole degrees of freedom [8]. This allows to calculate spectra of transitional nuclei and provides a microscopic interpretation of quantum phase transitions in finite fermion systems [9]. A number of illustrative calculations are presented and they are compared with results obtained in non-relativistic models based on Skyrme and Gogny effective interactions.[1] A. Ansari and P. Ring, Phys. Rev. C74, 054313 (2006).[2] J. Daoutidis and P. Ring, Phys. Rev. C80, 024309 (2009).[3] D. Pe~na Arteaga, E. Khan, and P. Ring, Phys. Rev. C79, 034311 (2009).[4] N. Paar, P. Ring, T. Nik_si_c, and D. Vretenar, Phys. Rev. C67, 034312 (2003).[5] E. Litvinova, P. Ring, and V. I. Tselyaev, Phys. Rev. C78, 014312 (2008).[6] E. Litvinova, P. Ring, V. I. Tselyaev, and K. Langanke, Phys. Rev. C79, 054312(2009).[7] J.-M. Yao, J. Meng, P. Ring, and D. Pe~na Arteaga, Phys. Rev. C79, 044312 (2009).[8] T. Nik_si_c, Z. P. Li, D. Vretenar, L. Pr_ochniak, J. Meng, and P. Ring, Phys. Rev. C79, 034303 (2009).[9] T. Nik_si_c, D. Vretenar, G. A. Lalazissis, and P. Ring, Phys. Rev. Lett. 99, 092502 (2007). * Work was supported in part by the DFG cluster of excellence Origin and Structure of the Universe(www.universe-cluster.de).
14-01-2011 At 04:00:00 PM
Speaker: Prof,. Amitabhy Vaimani, Brussels University, Belgium
Category: Seminar (String Theory)
Venue: Lecture Hall
In this talk I will discuss the use of the hidden G2(2)symmetry to construct black strings of minimal N=1 D=5 supergravity. Iwill present the construction of the most general black string withthree-commuting Killing symmetries in this theory. This solution has anumber of implications for extremal as well as non-extremal blackrings. Using a particular limit of this black string solution and theassociated dual Maldacena-Stominger-Witten (MSW) CFT, I will present aproposal for the microscopic realization of the Kerr-CFTcorrespondence.
17-01-2011 At 04:00:00 PM
Speaker: Mathieu Ehrhardt (Cambridge University)
Category: Seminar (String/Field theory)
Venue: Lecture Hall
25-01-2011 At 04:00:00 PM
Speaker: Sankhadeep Chakraborty
Category: Seminar (String Theory)
Venue: Lecture Hall
27-01-2011 At 04:00:00 PM
Speaker: Dr. Balaram Sahoo, HASYLAB at DESY, Germany
Category: General Seminar
Venue: Lecture Hall
In 1955 Willis Lamb received the noble prize, for the experimental observation of the ‘Lamb-shift’, a tiny energy shift of the bound atomic levels due to the interaction of the electron with virtual photons, which is at the heart of quantum electrodynamics and subsequent quantum field theories. However, Lamb shift was observed only for atomic gases. Although predicted about 35 years ago, the ‘collective lamb shift’ in real solid state samples was not observed, because (1) the atom-atom interaction masks the observable shift, ((2) the sample should be optically thin upon absorption and optically thick upon emission – such a sample was not realized in practice. We have overcome these problems by embedding a 57Fe (14.4 keV nuclear resonance) probe layer at the centre of a planar wave guide and exciting the 57Fe nuclei to a superradiant state by 14.4 keV single-photon pulsed-synchrotron radiation at a grazing incidence geometry (at the 1st wave guide mode of the cavity). Finally, by using the (coherent elastic) nuclear resonant scattering combined with Doppler energy analysis, we have measured, for the first time, the collective Lamb shift and the single-photon superradiance of 57Fe nuclei in two wave guide samples with 0.6 nm and 1.2 nm thickness of the 57Fe layer, respectively [1]. The details will be presented. Our observation and experimental method opens a new field for the study of light-mater interaction and the study of the Lamb shift and superradiance in quantum optics.[1] R. Röhlsberger, K. Schlage, B. Sahoo, S. Couet and R. Rüffer, Science, 328 (2010) 1248.
03-03-2011 At 04:00:00 PM
Speaker: Dr. Sudipto Poul Chowdhury, IACS, Kolkata
Category: HEP Seminar
Venue: Lecture Hall
11-03-2011 At 04:00:00 PM
Speaker: Mr.M.M.Mandal, VECC, Kolkata
Category: High Energy Experimental & Nuclear Physics Seminar
Venue: Lecture Hall
Jets are manifestation of hard scatterings of partons and its understanding in pp involves the partondistribution functions, the QCD-hard scattering processes and the long distance fragmentation phenomena.Therefore, jets can be used to study the parton level kinematics. Intrinsic transverse momentumof partons and the subsequent gluon radiations prior to hard scatterings [1], give rise to acoplanarityof dijets, depending on the Q2 of hard scatterings and the center of mass energy of collisions. Multiplescatterings of the hard scattered partons in cold nuclear matter may incorporate a modi cation of jetstructure.Two quantities commonly used to characterize the properties of jets are (i) jt, the transverse momentumof the jet fragments relative to the jet axis and (ii) kt, the transverse component of the momentumof the hard scattered partons. A measurement of the jet parameters, phj2t i and phk2t i [2] at STAR inpp collisions at ps = 62.4, 200 and 500 GeV using di-hadron correlation techniques is presented in widekinematics rage. 0 (Et = 6.5 to 18.5 GeV) and charged tracks (pt = 3.0-8.5 GeV/c) are used as triggerparticles in this analysis. A comparison of the jet parameters for pp and dAu (at various centralities) atps = 200 GeV will be presented.References[1] R.P Feynman, R.D. Field, and G.C. Fox, Phys. Rev. D18 3320(1978).[2] S.S. Adler et al., Phys. Rev. D74 072002(2006).
14-03-2011 At 04:00:00 PM
Speaker: Dr. R.Palit, TIFR, Mumbai
Category: NP Seminar
Venue: Lecture Hall
14-03-2011 At 11:00:00 AM
Speaker: Dr. K.Ramesh Kumar, IIT, Chennai
Category: Condensed Matter Experimental Seminar
Venue: Lecture Hall
15-03-2011 At 04:00:00 PM
Speaker: Dr. Revathi Naidu ,S.V. University, Tirupathi
Category: Experimental Condensed Matter Physics
Venue: Lecture Hall
Thin film solar cells based on chalcopyrite semiconductors have reached ahigh level performance over the last years both for laboratory scale cellsand commercial products. Research on CIGS-based photovoltaic cell isdeveloping towards the use of wide band-gap and non-toxic materials toreplace the cadmium sulphide buffer layer, which is used as an interfacialbuffer layer. A non-toxic photovoltaic technology poses fewer issues thana toxic technology and would clearly be a superior choice provided andother aspects are the same. Promising alternative materials used indifferent laboratories are mainly (sulfides, selenides and oxides) Zn andIn based buffer layers. These materials demonstrated their potential tolead high efficiency solar cells and modules comparable with standardchemical bath deposited (CBD) CdS. We have investigated the physicalproperties of alternative buffer layer materials (i.e., In2S3, ZnS, ZnMgO)employing different deposition techniques aiming to replace the CBD-CdSlayer in CIGS solar cells. The physical properties of such materials arestrongly depending on the deposition methods employed and processparameters maintained during the growth of the films. These properties canbe controlled and reproduced by precisely modulating of depositionparameters.
24-03-2011 At 04:00:00 PM
Speaker: Arti Garg (Univ. of California, Santa Cruz, USA)
Category: TPSC Seminar
Venue: Lecture Hall
28-03-2011 At 04:00:00 PM
Speaker: Sudhanwa Patra, PRL, Ahmedabad
Category: TPSC HEP Seminar
Venue: Lecture Hall
28-03-2011 At 04:00:00 PM
Speaker: Sudhanwa Patra, PRL, Ahmedabad
Category: TPSC HEP Seminar
Venue: Lecture Hall
04-04-2011 At 04:00:00 PM
Speaker: Dr. Kousik Dutta, DESY
Category: Colloquium
Venue: Lecture Hall
18-04-2011 At 04:00:00 PM
Speaker: Prof. Kalobaran Maiti,Department of Condensed Matter Physics and Materials Science,TIFR, Mumbai
Category: Colloquium
Venue: Lecture Hall
Antiparallel coupling of the impurity states with the conduction electronicstates leads to interesting phenomena in solid - the magnetic moments arecompletely compensated leading to a non-magnetic Fermi liquid phase in amagnetic material - this is known as Kondo effect. Such coupled electronicstates appear as a sharp feature at the chemical potential, called Kondoresonance feature. Employing high resolution photoemission spectroscopy, westudied the evolution of Kondo resonance feature in RB6 (R = La, Ce, Pr, Nd)and Ce2(RhCo)Si3 as a function of temperature that helps to probe thiseffect as a function of 4f binding energy and 4f-conduction electronhybridization strength. Experimental spectra of Kondo systems reveal thegrowth of multiple Kondo resonance features with decreasing temperaturerelative to the uncompensated local moment contributions that experimentallydemonstrates the Kondo effect. Ironically, the features near Fermi level inthe valence band spectra of PrB6, NdB6, Ce2RhSi3 etc also exhibit similartemperature dependence signalling the presence of Kondo compensation effectalthough their bulk physical properties do not exhibit Kondo effect.
04-05-2011 At 04:00:00 PM
Speaker: Dr. Sukanta De, School of Physics and CRANN Trinity College Dublin, Ireland
Category: CONDENSED MATTER PHYSICS SEMINAR
Venue: Lecture Hall
Transparent conductors play an important role in modern electronics.Commercially, this area is dominated by doped metal oxides, most commonlyindium tin oxide (ITO). However, the future of ITO as the main material inthis area may be limited for economic and technical reasons. In short, anew material is required that must be compatible with low temperature,large area deposition and must be flexible. This is in addition todisplaying high transparency, T, and low sheet resistance, Rs. It has beenknown for the past few years that flexibility and low temperatureprocessing can be achieved by the deposition of nanostructured thin films,often from the liquid phase. These are known to be stable under flexingand can be deposit on flexible substrate. Like carbon nanotubes, graphenecan be dispersed in common solvents as well as surfactants and can bedeposited as thin film. The most significant materials studied till noware carbon nanotube (CNT), graphene, metal gratings, and random networksof metallic nanowires. CNT and Metal nanowires network have propertiesthat are promising. CNT-PEDOT composites and Graphene-CNT hybrid films arebetter than CNT only. For most nanostructured films thin enough to displayT > 90% (industrial requirement), the conduction can be described bypercolation theory. This means DC conductivities are lower than in bulk,giving correspondingly higher sheet resistances, Rs. To improve ourunderstanding of the consequences of this, we develop a model whichrelates T to Rs in the percolation regime.
11-05-2011 At 04:00:00 PM
Speaker: Swapan Mahji, SINP, Kolkata
Category: TPSC HEP Seminar
Venue: Lecture Hall
11-05-2011 At 11:30:00 AM
Speaker: Prof.N.Gomathi, Indian Institute of Space Science and Technology,Trivandrum.
Category: General Seminar
Venue: Lecture Hall
Demanding beneficial surface properties of materials used in manybiomedical applications, to ensure the better performance of thebiomaterial without causing any adverse effect, necessitates the surfacemodification of the materials. Among the various surface modificationtechniques available, plasma treatment plays an important role bymodifying the surface properties of any material/any geometry, limiting itto a depth of few molecular layers in an eco-friendly manner. The coldplasma treatment is suitable for heat sensitive materials since it isoperated at near room temperature. Changes in physic-chemical propertiesof the materials make them suitable for biomedical applications. Some ofthe applications of plasma surface modification in biomedical applicationswill be touched upon in the talk with more emphasis on the bio and bloodcompatibility of radio frequency plasma surface modified polymers.
27-05-2011 At 04:00:00 PM
Speaker: Dr. Tae-Hun Lee, S.N.Bose Centre, Kolkata
Category: General Seminar
Venue: Lecture Hall
03-06-2011 At 04:00:00 PM
Speaker: Prof.M.K.Parida,HRI, Allahabad
Category: General Seminar
Venue: Lecture Hall
09-06-2011 At 04:00:00 PM
Speaker: Dr. Navinder Singh, PRL, Ahmedabad
Category: CMP (TPSC) Seminar
Venue: Lecture Hall
We propose a simple stochastic model which successfully explain the longcoherence effects observed in photosynthetic EET by 2D photon echoexperiments of G. S. Engel et. al. (Nature, {f 446} 782, (2007)). OurTwo-Component Phonon Spectrum (TCPS) model is based upon the division ofphonon degrees of freedom into systematic component (treated through Polarontransformation) and the stochastic component (treated through dynamicaldisorder). This model successfully explain the observed long coherence upto$ sim 600 fsec$ in EET experiments and it uses the information of homogeneous broadening from 2-D photon echo spectrum.
14-06-2011 At 04:00:00 PM
Speaker: Prof. B. P. Das, IIA, Bangalore
Category: General Seminar
Venue: Lecture Hall
Relativistic many-body theory has been successfully applied to a number of fundamental problems inphysics. The latest example of this being the application of this theory to the search of the electric dipole moment (EDM) of the electron.My talk will touch upon the connection between the EDM of the electron and the standard model of particle physics and also CP violation. However, its major emphasis will be on the development of aunique relativistic many-body theory and its crucial role in obtaining a new limit for the electron EDM.The implications of this limit will be discussed
16-06-2011 At 04:00:00 PM
Speaker: Samrat Bhowmick
Category: HEP Seminar
Venue: Lecture Hall
30-06-2011 At 03:00:00 PM
Speaker: Dr. Pallav Basu, Kentucky University
Category: General Seminar
Venue: Lecture Hall
I will provide an overview of current works in holographic superconductors, non-fermi liquids and related things.
08-07-2011 At 04:00:00 PM
Speaker: Payal Mohanty, VECC, Kolkata
Category: NP Seminar
Venue: Lecture Hall
Two-particle momentum correlations between pairs of identical particles produced in relativistic heavyion reactions can be analyzed to extract the information on the spatial and temporal structure of the source as well as the dynamics of fireball in Relativistic Heavy Ion collision.We have calculated twobody correlation function of lepton pairs produced from decay of virtual photon in central Au+Au collisions at the Relativistic Heavy Ion Collider. Our calculation includes contributions from the radiation of lepton pairs from a thermalized QuarkGluonPlasma (QGP) and the subsequent expanding hadron gas. The lepton pair interferometry provides a faithful probe of the details of the spacetime evolution and of the early stages of the system produced in Heavy Ion Collision. We have demonstrated that the study of mass dependence of various HBT radii extracted from the correlation functions of lepton pairs can be used as a powerful tool to characterize and distinguish the hadronic and the partonic phases and also focus on the collective expansion of the system. This study is carried out for Au+Au collisions at √ sNN = 200 GeV by solving relativistic hydrodynamical equations with boost invariance along the longitudinal direction. The equation of state is taken from lattice QCD calculations. The initial conditions for the solution of hydrodynamic equation is constrained by the measured single photon at RHIC. We obtain very different values for the HBT radii (Rside and Rout ) in the mass region around rhomeson and those beyond 1.2 GeV. The physical implications of these results and how these can be used to characterize the hadronic and partonic phases produced in high energy heavyion collisions will be discussed in the presentation
08-07-2011 At 11:00:00 AM
Speaker: Dr. Priti Sundar Mohanty (Lund University, Sweden)
Category: CMP Seminar
Venue: Lecture Hall
Cross-linked microgel particles constitute an interesting class of softcolloidal systems which possess a variable degree of softness and atuneable interaction potential that can be varied between hard spherecolloid and polymeric systems. These microgel colloids have a wide rangeof potential applications in drug delivery, sensing, fabrication ofphotonic crystals, template-based synthesis of inorganic nanoparticles,micro lenses, etc. Basically, these applications arise from theirstimulus-responsive nature, that is, their ability to undergo reversiblevolume phasetransitions in response to external stimuli such as a change intemperature, pH, and ionic strength of the surrounding medium. Moreover,it is also this responsiveness of the microgel particles which make theminteresting to use them as a model system for the investigation of manyfundamental thermodynamical phenomena.Here we study the phase behaviour of a particular class of soft-repulsivecolloids such as poly(N-isopropylacrylamide) ( PNIPAM ) microgel. Due to their soft- repulsivenature, microgels can interpenetrate or compress to a certain degree inorder to create states with densities far above the close packing (volumefraction=0.74) of hard sphere colloids. We look at the influence of theintrinsic softness of these particles on dynamical arrest, and investigatethe nature of the dense phases that exist at ultra-highdensities far beyond close packing. We use confocal laser scanningmicroscopy (CLSM) that allows us to track the particles in real time anddetermine quantities such the pair correlation function orthe mean square displacement of the particles as a function of effectivevolume fraction. We combine these experiments with static (SLS) anddynamic (DLS) light scattering, small-angle neutron (SANS) and small-anglex-ray scattering (SAXS) to obtain a full characterization of thestructural and dynamic properties of these suspensions at all relevantlength and time scales. In particular, a special variant of small-angleneutron scattering (SANS), experiments under so-called zero averagecontrast conditions, we also extract size and shape of the microgelparticles at all densities which allows us to completely decoupleinteractions and particle size and shape experimentally for the first time.
12-07-2011 At 04:00:00 PM
Speaker: Dr. Anurag Sahay
Category: HEP/CMP Seminar
Venue: Lecture Hall
In this talk we propose a novel method to characterize first order phasetransitions using the scalar curvature of the equilibrium thermodynamicstate space. Furthermore, our construction naturally characterizes theWidom line through the maxima of the correlation length. As anillustration, we use it in conjunction with the mean field Van der Waalsequation of state to predict the coexistence curve and the Widom line.Where closely applicable, it provides good agreement with experimentaldata. It generalizes to diverse systems like anti de Sitter black holes,which also exhibit first-order phase transitions.
15-07-2011 At 04:00:00 PM
Speaker: Sarira Sahu,Instituto de Ciencias Nucleares Universidad Nacional Autonoma de Mexico Mexico City
Category: General Seminar
Venue: Lecture Hall
Centaurus A is the nearest radio-loud AGN and is detected from radioto very high energy gamma-rays. Its nuclear spectral energydistribution shows two peaks, one in the far-infrared band and anotherat about 170 keV. Although, the flux from this nuclear region iswell explained by leptonic models, it fails to account for highenergy tail region above few GeV. We show that, within the jet, thecollision of Fermi accelerated high energy protons with the IC photonsaround the second peak region can produce multi-GeV to TeV gamma-raysand GeV neutrinos through delta-resonance which can explainsimultaneously, the observed GeV-TeV tail in the photon flux and theobserved cosmic ray events by Pierre Auger Observatory. We also estimatethe GeV neutrino flux from it.
25-07-2011 At 04:00:00 PM
Speaker: Prof. Sumit R. Das, University of Kentucky
Category: General Seminar
Venue: Lecture Hall
25-07-2011 At 11:00:00 AM
Speaker: Dr. Swarnendu Sarkar, Delhi University
Category: HEP / CMT Seminar
Venue: Lecture Hall
01-08-2011 At 04:00:00 PM
Speaker: Prof. Krishnendu Senguptaq, IACS
Category: Colloquium
Venue: Lecture Hall
02-08-2011 At 04:00:00 PM
Speaker: Dr. Jagjit Nanda,OakRidge National Lab., OakRidge, USA
Category: General Seminar
Venue: Lecture Hall
In this talk I shall give a general overview of the current state-of-theart research directions in the area of energy storage science andtechnology. Specific examples would be demonstrated in the area ofLithium-ion batteries and energy storage materials that can potentiallyrevolutionize the personal mobility and transportation sector. Thesedevelopments would lead to a sustainable “all electric†based technologythat could potentially eliminate the use of green house emitting fossilbased fuels. I shall provide a brief overview of various charge storingmechanism ranging from intercalation based transition metal oxidecompounds to conversion based reactions that can provide higher specificenergy and power density.The second part of the talk will focus on some of the research effortundertaken in my group including carbon fiber based batteries, high energydensity Li-ion electrode materials and their characterization.Fundamentals of Lithium atom transport and imaging using Neutron, scanningtransmission electron microscopy (STEM) and confocal micro-Ramanspectroscopy will be presented.
08-08-2011 At 04:00:00 PM
Speaker: Prof. Sourendu Gupta, TIFR, Mumbai
Category: Colloquium
Venue: Lecture Hall
18-08-2011 At 04:00:00 PM
Speaker: Dr. Sadhan Dash, (for the ALICE Collaboration) Universita and INFN di Torino, ITALY.
Category: General Seminar
Venue: Lecture Hall
Open Charm mesons produced in relativistic nuclear reactions are among themost direct probes to investigate the medium produced in these collisions. It isimportant to measure the production of as many charmed hadrons as possible,such as D0, D+, Ds, D and c. The measurement of their relative yield canprovide information on the hadronization mechanism and is necessary to reducethe systematic error on total charm cross-section. The ALICE experiment at theLHC is designed to perform such measurements at mid-rapidity by means of itsbarrel tracking detectors. The study on exclusive reconstruction of the D0, Ds,and D+ mesons through their hadronic decay channels will be presented for p+pcollisions at 7 TeV. The first results on D-meson spectra and the D+/D0 ratio willalso be shown.1
02-09-2011 At 04:00:00 PM
Speaker: P. K. Mohanty (SINP, Kolkata)
Category: General Seminar
Venue: Lecture Hall
09-09-2011 At 04:00:00 PM
Speaker: Dr.S. Dhara, IGCAR, Kalpakkam
Category: General Seminar
Venue: Lecture Hall
12-09-2011 At 04:00:00 PM
Speaker: Dinesh Topwal, Scientist ,Sincrotrone Trieste S.C.p.A.(ELETTRA) ,Trieste, ITALY
Category: General Seminar
Venue: Lecture Hall
13-09-2011 At 04:00:00 PM
Speaker: Manju Unnikrishnan,Sincrotrone Trieste S.C.P.A.(ELETTRA) ,Trieste, ITALY
Category: General Seminar
Venue: Lecture Hall
16-09-2011 At 04:00:00 PM
Speaker: Mahesh Kumar Surface Physics and Nanostructures Group, National Physical Laboratory, New Delhi
Category: General Seminar
Venue: Lecture Hall
The potential of surface science towards device fabrication isenormous. However, a trivial surface modification of the substratescan sometime alter the morphology and other properties of thesubstrates as well as the over-layer growth significantly. The kineticand thermodynamic control of the growth processes can form stabilizedlayered and nanostructures. I shall discuss about the 2D layers and 3Dnanostructure formation on the semiconductor and insulator substrateslike, Silicon, GaAs and Sapphire. Not only the various new phasediagrams have been proposed but also some of the existing ones arealso modified. We have used the surface chemical and structuralmodification to render substrate compatibility for epitaxial growth.Some of the examples would include the surface modification of GaAssubstrates for initial GaN formation, kinetically controlled selfassembled nanostructures of GaN and the epitaxial growth ofmultilayered and few-layered graphene on Sapphire substrates. Thegrowth of Graphene on insulator can lead to a breakthrough inutilizing insulator substrates as well for the epitaxial growth ofvarious materials like III-Nitrides.
19-09-2011 At 04:00:00 PM
Speaker: Prof. C.S. Unnikrishnan,TIFR, Mumbai
Category: Colloquium
Venue: Lecture Hall
I will discuss a new paradigm for physics of dynamics and relativity that is necessary to be consistent with modern cosmology. The fact that the fundamental theories of physics were completed well before any significant knowledge about the real universe and its enormous gravity was available necessitates a re-examination of these theories, especially that of dynamics and relativity. The results of this analysis, along with several experimental facts, reveal that the gravity of the cosmos determines the laws of motion and the propagation of light. In a grand generalization of Machian thought, Newton’s law of motion and the equivalence principle are natural consequences of the gravitational effect in the massive universe. All effects of relativity of motion, like length contraction and time dilation are in fact cosmic gravitational effects. Electrodynamics has physical effects that go beyond special relativity, requiring new experiments and analysis. Indeed, new experiments in our laboratory indicate clearly that the one-way speed of light is not a universal constant relative to moving observers, shattering the most cherished of our beliefs in physics and necessitating replacement of the special theory of relativity with a new ‘Cosmic Relativity’.
19-09-2011 At 11:00:00 AM
Speaker: Dr. Maheswar nayak (RRCAT, Indore)
Category: Exp.Physics Seminar
Venue: Lecture Hall
X-ray multilayers (MLs) - layered synthetic one-dimensional periodic microstructures – are playing an important role in the exploitation of x-rays, particularly soft x-ray/extreme ultra violet (XUV) region of the electromagnetic spectrum. However, understanding basic physics of x-ray MLs and controlling atomic distribution (hence surface/interface) over atomic depth scales in these nano-structured ML systems are crucial for optimum performance of optical elements. In this talk I will present the current state-of-the art research directions in the area of physics (basic and applied) of x-ray ML optics. I will discuss surface/interface studies through representative results of different material combinations. The talk will also cover correlation of structural parameters with tunable properties of x-ray MLs suitable for a variety of applications using synchrotron radiation.The second part of the talk will focus to uncover the underlying mechanism of resonance principle in x-ray scattering technique for basic surface/interface science with high sensitivity and unique additional feature compared to conventional x-ray scattering. Conventional x-ray reflectivity (XRR) probes spatial electron density distribution (within sensitive limit) but not directly atomic composition of the layer. A novel approach will be addressed not only the possible solution to low contrast physics issue of XRR but also an innovative approach to combine structural with chemical analysis using a single resonant scattering technique known for depth resolving sensitivity. We predicted resonant x-ray scattering combines layer sensitivity of reflectivity technique with short-range structural sensitivity such as chemical composition surrounding the resonating atom of spectroscopic technique due to element specificity and contrast variation mechanism of resonance effect. The sensitivity of resonant scattering to the presence of different chemical species around the resonating atoms is analogous to using deuteration as marker in neutron reflectivity. Novel idea will be demonstrated through representative results of different types of basic surface/interface studies near Si L-edge and boron K edge using synchrotron radiation.
20-09-2011 At 04:00:00 PM
Speaker: Prof. C.S. Unnikrishnan,TIFR, Mumbai
Category: General Seminar
Venue: Lecture Hall
This talk is a limited overview of the principles and techniques ofinterferometry with 'matter waves' - quantum interferometry to be moreprecise. I will focus on interferometers employing laser-cooled neutralatoms. The variety of ways in which atoms with internal states can respond tofields of external perturbations and 'interfere' is reflected in the richvariety of atom interferometers that can explore avenues not accessible tooptical interferometers. In particular, I will discuss the operation ofquantum interferometers in a gravitational field, stressing its ability tomeasure gravitational and inertial fields with unprecedented sensitivity. Thisalso leads to some fundamental issues of interpretation in the context ofgravitational redshift and time dilation. I will end with discussion whethergravimetry with quantum interferometers is equivalent to a measurement of thegravitational time dilation.
22-09-2011 At 04:00:00 PM
Speaker: Prof. M.K.Parida, HRI, Allahabad
Category: General Seminar
Venue: Lecture Hall
30-09-2011 At 04:00:00 PM
Speaker: Prof. D.P.Roy, Homi Bhabha Centre for Science Education,Tata Institute of Fundamental Research, Mumb
Category: Colloquium
Venue: Lecture Hall
11-10-2011 At 04:00:00 PM
Speaker: Dr. Satadeep Bhattacharjee, Division of Materials Theory, Uppsala University, Sweden
Category: General Seminar
Venue: Lecture Hall
In this presentation, I will briefly present some of the interestingstatic and dynamical aspects of few selected magnetic insulators andmetals.The electronic structure, vibrational properties and interestingdielectric nature of perovskites A(Ca,Sr,Ba)MnO3 will be discussed fromfirst principles, particularly the possibility to engineer a transitionmetal driven type-I multiferroicity in these oxides[1] will be specified.Then I will highlight some dielectric properties of Mn -doped SrTiO3 [2].In short, the quasiparticle electronic structure of thin films of localmoment systems like GdN and GdS will be reviewed [3]. Also I will presentsome of the results of the spin dynamics simulation for the magnetizationdynamics in an synthetic antiferromagnet subjected to a short pulse,particularly in terms of experimentally observed inertia like behavior init's magnetization dynamics[4]. Finally an effort to develop a generalformalism to describe the experimentally observed spin dynamics infemto-second time scale will be discussed [5].References:[1] S. Bhattacharjee, E. Bousquet and Philippe Ghosez , Phys. Rev.Lett.,102, 117602 (2009)[2] Debraj Choudhury, P. Mandal, A. Sundaresan, Umesh V. Waghmare,Satadeep Bhattacharjee, R. Mathieu, P. Lazor, Olle Eriksson, B. Sanyal,P. Nordblad, Ajay Sharma, S. V. Bhat, O. Karis, D. D. Sarma, cond-mat.,1009.4792, (2010),[3] S. Bhattacharjee and S.M Jaya, Eur. Phys. J. B 49, 305-311 (2006) .[4] S. Bhattacharjee, A. Bergman, A. Taroni, J. Hellsvik, B. Sanyaland O. Eriksson, arXiv:1109.1414, (2011).[5] S. Bhattacharjee, L.Nordstrom and J. Fransson (in manuscript).
11-10-2011 At 11:00:00 AM
Speaker: S M Yusuf, Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai
Category: General Seminar
Venue: Lecture Hall
12-10-2011 At 05:30:00 PM
Speaker: Prof. J.C. Pati, University of Maryland, USA
Category: Special Evening Talk
Venue: Lecture Hall
13-10-2011 At 04:00:00 PM
Speaker: Dr. Sankar Dhar,NUSNNI- NanoCore, National University of Singapore, Singapore
Category: Experimental Condensed Matter Physics Seminar
Venue: Lecture Hall
The modern device concepts have triggered an interesting scientific searchfor new multifunctional materials with novel set of physical properties.One of the scientifically challenging and technologically rewardingapproaches is to explore the possibilities of inducing new novelfunctionalities by incorporating foreign elements either via energeticions or chemically, thereby harnessing the benefits of both intrinsic andextrinsic properties. Alloying, interface, imperfection and dimensionalityplay critical roles in the manipulation process leading to unexpectedcatalysis processes inside solids, magnetic properties without anymagnetic element, thermal conductivities, electronic phase separation andtransports. In this talk, I will summarize and discuss the results of anumber of studies carried out on different elemental semiconductors, wideband gap oxides and layered structure materials.
14-10-2011 At 03:00:00 PM
Speaker: Prof. Jogesh Pati , Physics Dept., Universityi of Maryland, USA
Category: General Seminar
Venue: Lecture Hall
20-10-2011 At 04:00:00 PM
Speaker: Dileep Jatkar, HRI, Allahabad
Category: HEP Seminar
Venue: Lecture Hall
31-10-2011 At 04:00:00 PM
Speaker: Dr. Apoorva Nagar (IIT, Hyderabad)
Category: TPSC Seminar
Venue: Lecture Hall
Mutators are cells with a higher rate of mutations than normalcells. These mutations are base pair substitutions - errors that creep inwhen the genome is being copied during cell division. Mutator cells arepresent in small amounts in natural populations of some bacteria. Some kindsof cancer cells are also known to be mutators. A high mutation rate isusually a disadvantage but sometimes can also be an advantage to thespecies. In this talk, I will present my results on a simple model thattries to capture the evolutionary dynamics of mutator and normal cells. Ourmodel incorporates the conversion of normal cells to mutators and thereduction of fitness due to mutation. The mutators have a higher selectionpressure since a high mutation rate reduces fitness. The interplay ofconversion and the reduced fitness leads to an interesting phase diagram. Wehave predicted a new, all-mutator phase and calculated the phase transitionpoint analytically.
01-11-2011 At 04:00:00 PM
Speaker: Dr. Deepshikha Jaiswal Nagar, Hyderabad University
Category: General Seminar
Venue: Lecture Hall
Phase transitions occurring at absolute zero temperature and governedby a critical value of a variable like pressure, magnetic field,doping etc. are called quantum phase transitions and the point of thephase diagram where it happens the quantum critical point (QCP). Ahuge accumulation of entropy at the QCP leads to a competition betweendifferent ground states and hence, unusual behaviour in thethermodynamics and transport properties of systems close/at the QCP. Aone dimensional (1-d) spin ½ antiferromagnetic Heisenberg chain (AfHC)is expected to be quantum critical at a field H_s (saturation field)above which it undergoes a transition to a ferromagnetic state.Recently, it has been theoretically predicted that the divergence andsign change of Grüneisen parameter across the quantum critical pointcan be used as a novel technique to probe quantum criticality. For afield induced quantum critical point, the Grüneisen parameter is, infact, magnetocaloric effect (MCE) which is the heating or cooling of asystem adiabatically, in response to a changing magnetic field. Inthis talk, I will present measurements andtheoretical calculations of the MCE in a metal organic polymer systembuilt from Cu^2+ (S=½ ) ions, which is a very good realization of a1-d AfHC. We verify unambiguously the theoretical predictions anddemonstrate that the 1-d AfHC shows an extraordinarily large MCE and apronounced magnetic cooling effect near the QCP. Our results suggestthat quantum magnets near a H-induced QCP open up new possibilitiesfor realizing very efficient low-temperature coolants. We, therefore,suggest the MCE experiments as a new means of exploring quantumcriticality, one of the most interesting issues in modern condensedmatter physics.
01-11-2011 At 11:00:00 AM
Speaker: Dr.A.K.Arora,IGCAR, Kalpakkam
Category: General Seminar
Venue: Lecture Hall
08-11-2011 At 04:00:00 PM
Speaker: Sudhanwa Patra, PDF, IOP
Category: General Seminar
Venue: Lecture Hall
08-11-2011 At 11:00:00 AM
Speaker: Dr. Bhaskar Chandra Mohanty, Department of Mat. Sci. and Engg., Yonsei University Seoul, South Kore
Category: Seminar of General Interest (SKYPE presentation)
Venue: Lecture Hall
This talk concerns with various aspects of ZnO-based thin films forphotovoltaic applications. In particular, emphasis has been given tounderstand dynamics of thin film growth by studying temporal and spatialevolution of surface roughness within framework of the dynamic scalingtheory. The films deposited at room temperature by RF magnetron sputteringfrom a ceramic target follow anomalous (super-rough) scaling behaviorcharacterized by global roughness and growth exponents clearly distinctfrom the local ones. The observed anomalous scaling and high growthexponents are correlated to the shadowing effect arising due tonon-uniform flux distribution favored by the 30-tilt of thesubstrates. The scaling exponents and hence the growth dynamics are foundto be strongly dependent on the process parameter, namely the RF powerduring sputtering. While the roughness exponent α is stable at1.5±0.2, the growth exponents βlocal and β decrease with thedecrease in the RF power. A dominant anisotropic growth of crystallites athigh powers is believed to be the main reason for the power-dependentroughening behavior. Besides, thickness-dependent film properties, role ofsputtering configuration and influence of the RF power on film properties,which assume much importance from technological point of view, have beendiscussed. It has been shown that thickness-dependent stress cancounteract the typical carrier concentration dependent broadening of bandgap observed in degenerate semiconductors. The process parameters (forexample, RF power) and sputtering configuration are shown to havetremendous impact on film properties. A very brief introduction to ourother research efforts (that includes research in flexibleoptoelectronics, alternate absorber layers for inorganic solar cells,etc.) is also presented.
11-11-2011 At 04:00:00 PM
Speaker: Dr. Chandra Sekhar Rout, Birck Nanotechnology Center, Purdue University, USA
Category: General Seminar
Venue: Lecture Hall
Oriented assemblies of small crystals forming larger structuresare common in nature and crucial for forthcoming technologies asthey circumvent the difficulties of structural manipulation atmicroscopic scale. We have discovered two distinctive concentricassemblies of zinc oxide rods, wherein each rod has an intrinsicallypositive and a negative polar end induced by the noncentrosymmetricarrangement of Zn and O atoms. All the rods in a single assemblyemanate out of a central core maintaining a single polar direction.Due to growth along the two polar surfaces with different atomicarrangements, these assemblies are distinct in their intrinsicproperties and exhibit strong UV luminescence in the exterior ofZn-polar assemblies, unlike the O-polar assemblies. We have reportedsurface-enhanced Raman scattering (SERS) from Ag and Au nanoparticlesdecorated on thin carbon nanowalls (CNWs) grown by microwave plasmachemical vapor deposition. The Ag morphology is controlled byexposing the CNWs to oxygen plasma and through the electrodepositionprocess by varying the number of deposition cycles. The SERSsubstrates are capable of detecting low concentrations of rhodamine6G and bovine serum albumin, showing much higher Raman enhancementthan ordinary planar HOPG with Ag decoration. The major factorscontributing to this behavior include: high density of Agnanoparticles, large surface area, high surface roughness, and theunderlying presence of vertically oriented CNWs. The relativelysimple procedure of substrate preparation and nanoparticledecoration suggests that this is a promising approach forfabricating ultrasensitive SERS substrates for biological andchemical detection at the single-molecule level, while alsoenabling the study of fundamental SERS phenomena.
14-11-2011 At 04:00:00 PM
Speaker: Dr.A. Shukla, RGIPT, Raeborali
Category: General Seminar
Venue: Lecture Hall
Double beta decay (DBD), first predicted in 1935 by Maria Goeppert-Mayer, has evolved from a marginal activity in nuclear physics to one of the top priority research areas of the physics worldwide, for understanding neutrinos primarily and also for constraining the nuclear structure models to a large extent. In last 75 years, a large progress has been made in the field of double beta decay studies, experimentally as well as theoretically, resulting in successful observation of two neutrino double beta decay for several nuclei and pinning down the mass of neutrino to sub eV scale (~0.2-0.5 eV; depending on the choice of nuclear matrix element) - through a single claim for the observation of neutrinoless double beta decay of 76Ge. Though, this clam, still needs to be verified by other experiments for 76Ge and other candidate nuclei as well, it has greatly boosted up the research projects related to this particular lepton violating process. More importantly, Indian efforts, however at primitive stage presently, are also on to develop a state of the art double beta decay experiment at India based Neutrino Observatory (INO). In the present talk, I will discuss our results for DBD and also present an overview of the current status along with future prospects of DBD studies.
15-11-2011 At 04:00:00 PM
Speaker: Mr. Amit Sharma, National Centre for Biological Sciences,(NCBS - TIFR) Bangalore
Category: General Seminar
Venue: Lecture Hall
A protein called DNA Polymerases is capable of creating new DNA strands by incorporating the monomeric units of DNA called nucleotides opposite the single stranded parent DNA in a Watson Crick manner (A:T and G:C). DNA polymerases are therefore centrally involved in the replication of DNA. In order to carry out this crucial function, these replicative DNA polymerase molecules exhibit extremely high accuracy and processivity (measure of the no. of nucleotides added by a polymerase per association with a DNA). The presence of damaged nucleotides in the genome (DNA code for any organism) is highly inhibitory to the activity of these DNA Polymerases. DNA can be damaged by a variety of external (radiation, chemicals) and internal (free radicals, reactive intermediates) agents. Replicative DNA Polymerases are not capable of stabilizing the damaged nucleotide and the correct incoming nucleotide in their active sites which leads to the stalling of the replication machinery. To overcome this predicament it is seen that all organisms have specialized DNA Polymerases grouped under the Y-family of DNA Polymerases. The members of this family usually exhibit low-fidelity (ability to pair in Watson Crick manner) and low-processivity and are able to incorporate nucleotides opposite various kinds of damaged nucleotides. It is believed that once these molecules help the replication machinery cross the damage they are replaced by normal replicative DNA Polymerases. In addition, it has also been suggested that the low-fidelity of these molecules is exploited to generate adaptive mutations that can relieve selection pressure arising from adverse environmental conditions. This might be especially true in case of prokaryotes (bacterial organisms) where the expression of these molecules is controlled by transcriptional mechanisms that deal with stress. We have carried out structural and functional studies on one of theY-family protein in Mycobacterium smegmatis (bacterial organism similar toTuberculosis and non pathological), MsDpo4. The aim is to provide atopological and chemical description of MsDpo4 in order to understand the relation between structure and function in case of Y- Family DNA Polymerases in prokaryotes. We have seen that this protein prefers Watson-Crick mode of base pairing and it is also capable of promoting mismatches. Steady-state kinetic analysis shows that this protein exhibits significant ability to promote G:T and T:G mismatches and thus has the biochemical capacity to participate in adaptive mutagenesis. MsDpo4 is also capable of carrying out synthesis across the damaged DNA. The structure of MsDpo4 has been determined to a resolution of 2.6 Ã…. The structure suggests that one of the domain of this protein exhibits conformational heterogeneity. The possible implications of this observation will be discussed.
21-11-2011 At 04:00:00 PM
Speaker: Dr.Sarmistha Banik, SINP, Kolkata
Category: NP Seminar
Venue: Lecture Hall
Several novel phases with large strangeness fraction such as, hyperon matter, quarkphase and Bose-Einstein condensates of antikaons are theoretically predicted at the highdensity core of neutron stars. Within the framework of the traditional meson exchangepicture known as the relativistic mean field (RMF) model, we study the equation ofstate (EoS) in the dense matter at the core of compact stars, formed in the core collapsesupernovas.The EoS of hot and dense matter plays a fundamental role in the understanding ofcore-collapse supernova. A phase transition from hadronic to exotic phases might occurin the early post-bounce phase of a core collapse supernova. We investigate the emergenceof strange hyperons in the dynamical collapse of a non-rotating massive star to a blackhole. We follow the dynamical formation and collapse of a protoneutron star (PNS) fromthe gravitational collapse of a 40M star adopting the newly constructed Shen hyperonicEOS. We also study the neutrino signals that may be used as a probe to core collapsesupernova. We compare the results with those of Shen nuclear EoS and understand therole of strange hyperons in the core collapse.Finally we discuss about our ongoing work on generating a full table of antikaon EoSfor a wide spectrum of temperature, density and proton fraction, which should be usefulfor supernova simulations.
23-11-2011 At 04:00:00 PM
Speaker: Ambresh Shivaji
Category: HEP Seminar
Venue: Library Lecture Hall
30-11-2011 At 04:00:00 PM
Speaker: Dr. Jyoti Ranjan Mohanty,Technical University Berlin, Germany
Category: General Seminar
Venue: Lecture Hall
Modern magnetic devices (GMR read heads, magnetic sensors, hard disks andspintronics devices) relies on storing or manipulating magneticinformation in smaller length scales (nm’s) at faster time scales(nano-seconds to femto- seconds). It is very important to know themagnetic structure in order to understand the magnetic device. To advancenanoscience and nanotechnology, we have to be able to understand howmaterials behave at the nanoscale. Advancement of nano-science allows usto prepare structure in nanometer scale both by self-assembly and electronbeam lithography. X-ray magnetic characterization provide us informationon nanoscale with element specificity, chemical sensitivity, sensitivityto charge, orbital and spin ordering, high spatial resolution,polarization capability and faster time scales (dynamics using coherence,for coherent diffraction imaging and XPCS) and pump-probe techniques. Inthis talk I will present an overview of thin film magnetism and ultrafastmagnetic dynamics of magnetic multilayers exhibiting ordered stripes dueto perpendicular magnetic anisotropy (PMA). I will present a rather newand demanding technique to take image without a lens. One can see magneticstructure at the nanoscale level without using any lenses. One immediateapplication of this lens-less X-ray microscope is the development ofsmaller data storage devices for computers that can hold more memory.I will address the evolution of magnetic systems as a function of magnetic
01-12-2011 At 11:00:00 AM
Speaker: Rajdeep Sensarma (Univ. of Maryland, USA)
Category: Condensed Matter Theory Seminar
Venue: Lecture Hall
Cold atoms have emerged as a new and exciting platform to study thephysics of strongly interacting quantum many body systems relevant tocondensed matter physics. In this talk I will discuss how dynamics of coldatoms close to equilibrium can be used to reveal many body correlationsand detect novel phases in these systems. I will also discuss the dynamicsof these systems far from equilibrium, focusing on the relaxation of highenergy excitations in Fermionic systems.
05-12-2011 At 04:00:00 PM
Speaker: Swarup Kumar Majee, National Taiwan University
Category: HEP Skype Seminar
Venue: Lecture Hall
Besides supersymmetry, the other prime candidate of physics beyond the StandardModel (SM), crying out for verification at the CERN Large Hadron Collider (LHC), is extra-dimension. To hunt for effects of Kaluza–Klein (KK) excitations of known fermions and bosons is very much in the agenda of the LHC. These KK states arise when the SM particles access the extra space-like dimension(s). We consider here a 5-dimensional universal extra-dimension (UED) scenario. The Kaluza-Klein (KK) number is conserved at all tree level vertices. This entails the production of KK states in pairs and renders the lightest KK particle stable, which leaves the detector carrying away missing energy. The splitting between different KK flavors is controlled by the zero mode masses and the bulk- and brane-induced one-loop radiative corrections. We concentrate on the production of an n=1 KK electroweak gauge boson in association with an n=1 KK quark. This leads to a signal consisting of one jet, one or more leptons and missing pt. For definiteness we usually choose the inverseradius of compactification to be R1 = 500 GeV, which sets the scale of the lowest lying KK states. We show that with 10 fb1 integrated luminosity at the LHC with √s= 14 TeV this signal can be detected over the SM background by imposing appropriate kinematic cuts. We record some of the expectations for a possible intermediate LHC run at √s = 10 TeV and also exhibit the integrated luminosity required to obtain a 5 σ signal as a function of R1
05-12-2011 At 11:00:00 AM
Speaker: Ramesh Chandra Nath, Indian Institute of Science Education and Research,Thiruvananthapuram
Category: General Seminar
Venue: Lecture Hall
Low-dimensional spin systems are one of the actively studied subjects insolid state physics due to the possibility to observe numerous quantumphenomena and to interpret these phenomena within relatively simple models(e.g., Ising or Heisenberg models for different lattice types). Aninteresting phenomenon in spin physics is the formation of a spin liquid –a strongly correlated ground state lacking long-range magnetic order. Spinliquids originate from quantum fluctuations that are particularly strongin systems with reduced dimensionality and low spin value. Thefluctuations can be further enhanced by introducing magnetic frustrationwhich impedes long-range ordering of the system. This talk mainly focuseson frustrated two-dimensional square lattice systems.The spin-1/2 frustrated square lattice (FSL) is one of the simplest modelsgiving rise to a spin liquid ground state. In this model (also known asthe J1 − J2 model), magnetic moments on a square-lattice aresubjected to nearest-neighbor interaction J1 along the side of the squareand next-nearest-neighbor interaction J2 along the diagonal of the square.Extensive theoretical research on the FSL model has been done in the pastand a rich phase diagram has been proposed. Despite numerous theoreticalinvestigations, experimental realizations of the J1 − J2 modelcompounds are scarce. Recently we synthesized and investigated thephysical properties of two new compounds Pb2VO(PO4)2 and BaCdVO(PO4)2 viamagnetization, heat capacity, and nuclear magnetic resonance (NMR)measurements. These two compounds were found to be strongly frustrated J1− J2 square lattice compounds with ferromagnetic J1 andantiferromagnetic J2. Based on the frustration ratio J2/J1, BaCdVO(PO4)2(J2/J1 = 0.9) is placed more close to the quantum spin liquidregime of the phase diagram than the Pb2VO(PO4)2 (J2/J1 = 1.76).Both compounds undergo magnetic ordering at TN ≈ 1 K and 3.6 K,respectively, likely towards a columnar antiferromagnetic state. Using 31PNMR on a large single crystal we investigated the static and dynamicproperties of Pb2VO(PO4)2. From the NMR spectral measurements below TN, weobtained direct evidence for a columnar antiferromagnetic ground state.This ground state is consistent with the phase diagram, expected based onthe observed J2/J1 ratio.
07-12-2011 At 04:00:00 PM
Speaker: Sanjib Kumar Agarwalla, Universitat de Valencia
Category: HEP Skype Seminar
Venue: Lecture Hall
First of all, we will take a look at our present global understanding of theneutrino mass-mixing parameters and will identify the major unknowns in this sector.Then we will discuss the physics reach of the upcoming reactor and acceleratorneutrino oscillation experiments in addressing these unsolved issues.Next, we will analyze the impact of large theta(13) on the optimization offuture long baseline superbeam experiments with a special emphasis onpotential European scenarios which are proposed to enhance our knowledgeof neutrino oscillations well beyond what can be anticipated from ongoing andplanned experiments worldwide.
07-12-2011 At 11:00:00 AM
Speaker: Santosh K. Rai, Oklahoma State University
Category: HEP Skype Seminar
Venue: Lecture Hall
LHC being a hadron machine final states withmulti-leptons are rare compared to multi-jet final states.In the standard model the events become more rare asthe lepton multiplicity increases in the final state. I showthat such final states turn out to be excellent probes fordiscovering new physics beyond the standard model. Ialso show how different kinematic properties of such leptonicfinal states can help in distinguishing different speculativeideas of new physics.
09-12-2011 At 04:00:00 PM
Speaker: Prof. Peter A. Dowben, University of Nebraska-Lincoln, USA
Category: Colloquium
Venue: Lecture Hall
Wave vector-resolved inverse photoelectron spectroscopy (IPES)measurements have been used to demonstrate that there is a large variationof interfacial charge transfer between the supporting substrate andgraphene. The results were obtained for graphene grown by chemical vapordeposition(CVD) on a range of dielectric or metallic substrates. Monolayer graphenegrown by CVD on monolayer BN(0001)/Ru(0001) exhibits strong chargetransfer from the substrate to graphene of 0.07(1) e- per carbon atom,evident from the filling of the π* band and displacement of the Fermilevel. Inversephotoelectron spectroscopy (IPES) measurements of CVD single layergraphene on Ru indicate a substrate-to-graphene charge transfer from thesubstrate of 0.06(1) e- per carbon atom, in agreement with reportedangle-resolved photoemission results. The IPES spectra of CVD single layergraphene onNi(polycystalline), and on Cu(polycystalline) indicate 0.03(1) e- percarbon atom charge transfer from Ni and Cu substrates. IPES measurementsindicate that single layer graphene on MgO(111) exhibit 0.02(1) e- percarbon atom charge is transferred from graphene to the MgO substrate.Additionally, IPES and photoemission data, when combined, along withcharging in the retarding potential vacuum diode geometry indicate thatsingle layer graphene/MgO(111) exhibits a band gap. These data demonstratethat IPES is one effective method for precise measurement ofsubstrate/graphene charge transfer and related electronic interactions, inpart because of the extreme surface sensitivity of the technique. Lookingto the future, comparison of graphene electronic structure on manysubstrates may suggest new strategies for extrinsic doping of graphene forcontrolled mobilities for device applications. The opening of a band gapcan be related to a reduction in symmetry from C6 to C3 or looking at itanother way, making the A and B site of graphene chemically inequivalent.Graphene is not simply chemically inert. We find that the photoemissionand inverse photoemission final states are better screened for dipolarmolecules, with a large intrinsic dipole of 10 Debyes, on gold than isobserved to be the case on graphene on copper, and this is evident in alarger highest occupied molecular orbital to lowest unoccupied molecularorbital gap.Work done with Lingmei Kong,1 Cameron Bjelkevig,2 Sneha Gaddam,2 Mi Zhou,2Young Hee Lee,3 Gang Hee Han,3 Hae Kyung Jeong,4 Ning Wu,1 ZhengzhengZhang,1 Jie Xiao,1 and Jeffry A. Kelber21) University of Nebraska-Â‐Lincoln2) University of North Texas.3) Sungkyunkwan University, Suwon, 440-Â‐746 Korea (ROK)4) Daegu University, Gyeongsan, 712-Â‐714 Korea (ROK)
09-12-2011 At 03:00:00 PM
Speaker: Tanumoy Pramanik, SNBCBS
Category: Quantum Information Seminar
Venue: Library Lecture Hall
13-12-2011 At 04:00:00 PM
Speaker: Prof. M.P. Das, Australian National University, Canberra
Category: General Seminar
Venue: Library Lecture Hall
In meso/nanoscopic systems three significant issues are of pivotalimportance: (i) due to the smallness of their size, quantum effects arecrucial, (ii) for the same reason, the surface-to-volume ratio is largeand this characteristic feature induces certain unique and fascinatingeffects, and (iii) the system remains in active contact with itsenvironment, which induces a variety of novel properties. In view of theenormity of this subject, we shall limit our discussions to certainessential and fundamental science, with a number of non-trivial examples.We shall highlight current activity on various issues mainly related toelectron transport in meso/nano systems. Models relevant to the latterhave some real application to molecular electronics.
15-12-2011 At 04:00:00 PM
Speaker: Mr. M.Bhuyan, Sambalpur University
Category: General Seminar
Venue: Library Lecture Hall
Within the framework of the nucleon-meson exchange picture known as therelativistic mean field (RMF) model, we study the bulk properties ofnuclei at different regions of the nuclear chart. Mostly the structure ofsuperheavy elements and the sub-structure of intermediate mass nuclei willbe discussed. We will also derive the NN interaction from the RMFlagrangian which will be apply to study the cluster radioactivity andproton emission phenomenon.References:[1] S. K. Patra, M. Bhuyan, M. S. Mehta, Raj K. Gupta Phys. Rev. C 80034312 (2009).[2] M. Bhuyan et al. Phys. Rev. C 82, 064602 (2010).[3] M. Bhuyan et al. Phys. Rev. C 84, 014317 (2011).[4] M. Bhuyan et al. Int. J. Mod. Phys. E 20 2217 (2010).[5] B. K. Sahu, M. Bhuyan, S. Mohapatro, S. K. Patra. Int. J. Mod. Phys. E 20 2227 (2011).[6] B. B. Singh, M. Bhuyan, Raj. K. Gupta, S. K. Patra, J. Phys. G 34(press) 2012.[7] M. Bhuyan et al. Phys. Lett. B (communicated)
26-12-2011 At 04:00:00 PM
Speaker: Prof. X.Vinas, University of Barcelona
Category: General Seminar
Venue: Lecture Hall
Two issues are treated in this talk: (i) the generic fact that if a fermionic superfluid in the BCS regime overflows from a narrow container into a much wider one, pairing is much suppressed at the overflow point. Physical examples in cold atoms, neutron stars and nuclei where this feature may play an important role are discussed. (ii) A Thomas-Fermi (TF)approach to inhomogeneous superfluid Fermi-systems is presented and shown that it works well in cases where the Local Density Approximation (LDA) breaks down.
27-12-2011 At 04:00:00 PM
Speaker: Prof. Hiranmaya Mishra, Physical Research Laboratory,Ahmedabad
Category: TPSC Seminar of General Interest
Venue: Lecture Hall
Ultra strong magnetic field could be there in the interior of neutron stars.Strong magnetic field can also be produced inheavy ion collision experiments. I will discuss chiral symmetry breaking inhot and dense quark matter in presenceof strong magnetic field within a 3 flavor Nambu Jona Lasinio model. Whilemagnetic catalysis of chiral symmetrybreaking is expected for hot matter, inverse magnetic catalysis for chiralsymmetry breaking is expectedat finite chemical potential. The equation of state for strange quark matteris derived within the model. The effect of pressureanisotropy of dense quark matter in presence of magnetic field in the grossstructural properties of neutron stars will also be discussed.
29-12-2011 At 11:00:00 AM
Speaker: Arnab Das
Category: Condensed Matter Theory Seminar
Venue: Lecture Hall