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 New Distributed Time Synchronization Protocol for Multihop Wireless Networks

Abstract: A distributed algorithm to achieve accurate time synchronization in large multihop wireless networks is presented. The central idea is to exploit the large number of global constraints that have to be satisfied by a common notion of time in a multihop network. If, at a certain instant, Oij is the clock offset between two neighboring nodes i and j, then for any loop i1, i2, i3 , ..., in, in + 1 - i1 in the multihop network, these offsets must satisfy the global constraint Sigma k = 1 nOik, ik + 1 = 0. Noisy estimates Ocirc ij of Oij are usually arrived at by bilateral exchanges of timestamped messages or local broadcasts. By imposing the large number of global constraints for all the loops in the multihop network, these estimates can be smoothed and made more accurate. A fully distributed and asynchronous algorithm which functions by simple local broadcasts is designed. Changing the time reference node for synchronization is also easy, consisting simply of one node switching on adaptation, and another switching it off. Implementation results on a forty node network, and comparative evaluation against a leading algorithm, are presented

Upper Limits on the Rates of Binary Neutron Star and Neutron Star-Black Hole Mergers from Advanced LIGO’s First Observing Run

Abstract: We report here the non-detection of gravitational waves from the merger of binary–neutron star systems and neutron star–black hole systems during the first observing run of the Advanced Laser Interferometer Gravitational-wave Observatory (LIGO). In particular, we searched for gravitational-wave signals from binary–neutron star systems with component masses $\in [1,3]\,{M}_{\odot }$ and component dimensionless spins <0.05. We also searched for neutron star–black hole systems with the same neutron star parameters, black hole mass $\in [2,99]\,{M}_{\odot }$, and no restriction on the black hole spin magnitude. We assess the sensitivity of the two LIGO detectors to these systems and find that they could have detected the merger of binary–neutron star systems with component mass distributions of 1.35 ± 0.13 M ⊙ at a volume-weighted average distance of ~70 Mpc, and for neutron star–black hole systems with neutron star masses of 1.4 M ⊙ and black hole masses of at least 5 M ⊙, a volume-weighted average distance of at least ~110 Mpc. From this we constrain with 90% confidence the merger rate to be less than 12,600 Gpc−3 yr−1 for binary–neutron star systems and less than 3600 Gpc−3 yr−1 for neutron star–black hole systems. We discuss the astrophysical implications of these results, which we find to be in conflict with only the most optimistic predictions. However, we find that if no detection of neutron star–binary mergers is made in the next two Advanced LIGO and Advanced Virgo observing runs we would place significant constraints on the merger rates. Finally, assuming a rate of ${10}_{-7}^{+20}$ Gpc−3 yr−1, short gamma-ray bursts beamed toward the Earth, and assuming that all short gamma-ray bursts have binary–neutron star (neutron star–black hole) progenitors, we can use our 90% confidence rate upper limits to constrain the beaming angle of the gamma-ray burst to be greater than $2\buildrel{\circ}\over{.} {3}_{-1.1}^{+1.7}$ ($4\buildrel{\circ}\over{.} {3}_{-1.9}^{+3.1}$).

The QCD equation of state in background magnetic fields

Abstract: We determine the equation of state of 2+1-flavor QCD with physical quark masses, in the presence of a constant (electro)magnetic background field on the lattice. To determine the free energy at nonzero magnetic fields we develop a new method, which is based on an integral over the quark masses up to asymptotically large values where the effect of the magnetic field can be neglected. The method is compared to other approaches in the literature and found to be advantageous for the determination of the equation of state up to large magnetic fields. Thermodynamic observables including the longitudinal and transverse pressure, magnetization, energy density, entropy density and interaction measure are presented for a wide range of temperatures and magnetic fields, and provided in ancillary files. The behavior of these observables confirms our previous result that the transition temperature is reduced by the magnetic field. We calculate the magnetic susceptibility and permeability, verifying that the thermal QCD medium is paramagnetic around and above the transition temperature, while we also find evidence for weak diamagnetism at low temperatures.

GLEAM : The GaLactic and Extragalactic All-sky MWA survey

Abstract: © Astronomical Society of Australia 2015; published by Cambridge University Press. This is an Open Access article distributed in accordance with the terms of the Creative Commons Attribution (CC BY 4.0) license, which permits others to distribute, remix, adapt and build upon this work, for commercial use, provided the original work is properly cited. See: http://creativecommons.org/licenses/by/4.0/

Inclusive measurement of the photon energy spectrum in b → sγ decays

Abstract: We report a fully inclusive measurement of the flavor changing neutral current decay $b\ensuremath{\rightarrow}s\ensuremath{\gamma}$ in the energy range $1.8\text{ }\mathrm{G}\mathrm{e}\mathrm{V}\ensuremath{\le}{E}_{\ensuremath{\gamma}}^{*}\ensuremath{\le}2.8\text{ }\mathrm{G}\mathrm{e}\mathrm{V}$, covering 95% of the total spectrum. Using $140\text{ }\mathrm{f}{\mathrm{b}}^{\mathrm{\ensuremath{-}}\mathrm{1}}$, we obtain $\mathcal{B}(b\ensuremath{\rightarrow}s\ensuremath{\gamma})=(3.55\ifmmode\pm\else\textpm\fi{}{0.32}_{\ensuremath{-}0.31\ensuremath{-}0.07}^{+0.30+0.11})\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}$, where the errors are statistical, systematic, and from theory corrections. We also measure the first and second moments of the photon energy spectrum above $1.8\text{ }\mathrm{G}\mathrm{e}\mathrm{V}$ and obtain $\ensuremath{\langle}{E}_{\ensuremath{\gamma}}\ensuremath{\rangle}=2.292\ifmmode\pm\else\textpm\fi{}0.026\ifmmode\pm\else\textpm\fi{}0.034\text{ }\mathrm{G}\mathrm{e}\mathrm{V}$ and $\ensuremath{\langle}{E}_{\ensuremath{\gamma}}^{2}\ensuremath{\rangle}\ensuremath{-}\ensuremath{\langle}{E}_{\ensuremath{\gamma}}{\ensuremath{\rangle}}^{2}=0.0305\ifmmode\pm\else\textpm\fi{}0.0074\ifmmode\pm\else\textpm\fi{}0.0063\text{ }{\mathrm{G}\mathrm{e}\mathrm{V}}^{2}$, where the errors are statistical and systematic.