Tata Institute of Fundamental Research

About: Tata Institute of Fundamental Research is a education organization based out in Mumbai, Maharashtra, India. It is known for research contribution in the topics: Magnetization & Large Hadron Collider. The organization has 7786 authors who have published 21742 publications receiving 622368 citations. The organization is also known as: TIFR.

A strongly coupled anisotropic fluid from dilaton driven holography

Abstract: We consider a system consisting of 5 dimensional gravity with a negative cosmological constant coupled to a massless scalar, the dilaton. We construct a black brane solution which arises when the dilaton satisfies linearly varying boundary conditions in the asymptotically AdS 5 region. The geometry of this black brane breaks rotational symmetry while preserving translational invariance and corresponds to an anisotropic phase of the system. Close to extremality, where the anisotropy is big compared to the temperature, some components of the viscosity tensor become parametrically small compared to the entropy density. We study the quasi normal modes in considerable detail and find no instability close to extremality. We also obtain the equations for fluid mechanics for an anisotropic driven system in general, working upto first order in the derivative expansion for the stress tensor, and identify additional transport coefficients which appear in the constitutive relation. For the fluid of interest we find that the parametrically small viscosity can result in a very small force of friction, when the fluid is enclosed between appropriately oriented parallel plates moving with a relative velocity.

Strong itinerant magnetism in ternary boride CeRh3B2

Abstract: Reports a high-temperature itinerant ferromagnet CeRh3B2 which orders magnetically at 115K. The magnetic ordering seems to be intrinsic and presumably arises from the Rh d-band. Similar compounds of La, Pr and Nd do not show any magnetic ordering down to 77K.

Measurement of the Υ(1S), Υ(2S), and Υ(3S) Polarizations in pp Collisions at s√=7 TeV

Abstract: The polarizations of the Υ(1S), Υ(2S), and Υ(3S) mesons are measured in proton-proton collisions at √s=7 TeV, using a data sample of Υ(nS)→μ^+μ^- decays collected by the CMS experiment, corresponding to an integrated luminosity of 4.9 fb^(-1). The dimuon decay angular distributions are analyzed in three different polarization frames. The polarization parameters λ_ϑ, λ_φ, and λ_(ϑφ), as well as the frame-invariant quantity λ˜, are presented as a function of the Υ(nS) transverse momentum between 10 and 50 GeV, in the rapidity ranges |y|<0.6 and 0.6<|y|<1.2. No evidence of large transverse or longitudinal polarizations is seen in the explored kinematic region.

Interference Effect in Electron Emission in Heavy Ion Collisions with H~2 Detected by Comparison with the Measured Electron Spectrum from Atomic Hydrogen

Abstract: Direct evidence of the interference effect in the electron emission spectra from ionization of molecular hydrogen in collisions with bare C and F ions at relatively low collision energies is presented. Oscillations due to the interference are deduced by comparing the measured double differential cross sections of the electrons emitted from molecular hydrogen to those emitted from atomic hydrogen, rather than using the calculated cross sections for H as in a previous report. We believe these experimental data provide stronger support for the evidence of the interference effect. We show that it is not only a feature of very high energy collisions, but also a feature to be observed in relatively lower energy collisions.

Thermal generation of cosmological seed magnetic fields in ionization fronts

Abstract: Quasar spectra indicate that the intergalactic medium (IGM) was reionized at some redshift z≥ 5, probably due to discrete sources of ionizing photons like QSOs and young galaxies. In such a circumstance, ionization fronts will expand away from these sources until they percolate and encompass a substantial part of the IGM. The pressure gradients in the ionization front acting on electrons can lead to a thermally generated electric field. This field will have a non-vanishing curl and hence imply a growing magnetic field, provided the pressure gradient in the front is not parallel to the density gradient. Such a situation obtains naturally in the cosmological context because the IGM harbours primordial (growing) density fluctuations whose density gradients are not correlated with the pressure gradients produced by an arbitrarily placed ionizing source. In this process, magnetic fields can be thermally generated, over a good fraction of the IGM. In particular, they can have strengths ~3 × 10-20 G on galactic scales, and can serve as seed fields for further amplification by the galactic dynamo.