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.

Chemical composition of nuclei of z > 22 in cosmic rays using meteoritic minerals as detectors.

Abstract: New techniques considerably extend the usefulness of meteoritic minerals in the study of the composition of prehistoric cosmic radiation.

Study of vector boson scattering and search for new physics in events with two same-sign leptons and two jets

Abstract: A study of vector boson scattering in pp collisions at a center-of-mass energy of 8 TeV is presented. The data sample corresponds to an integrated luminosity of 19.4 inverse femtobarns collected with the CMS detector. Candidate events are selected with exactly two leptons of the same charge, two jets with large rapidity separation and dijet mass, and moderate missing transverse energy. The signal region is expected to be dominated by electroweak same-sign W-boson pair production. The observation agrees with the standard model prediction. The observed significance is 2.0 standard deviations, where a significance of 3.1 standard deviations is expected based on the standard model. Cross section measurements for W+/- W+/- and WZ processes in the fiducial region are reported. Bounds on the structure of quartic vector-boson interactions are given in the framework of dimension-eight effective field theory operators, as well as limits on the production of doubly-charged Higgs bosons.

First search for gravitational waves from known pulsars with advanced LIGO

Abstract: We present the result of searches for gravitational waves from 200 pulsars using data from the first observing run of the Advanced LIGO detectors. We find no significant evidence for a gravitational-wave signal from any of these pulsars, but we are able to set the most constraining upper limits yet on their gravitational-wave amplitudes and ellipticities. For eight of these pulsars, our upper limits give bounds that are improvements over the indirect spin-down limit values. For another 32, we are within a factor of 10 of the spin-down limit, and it is likely that some of these will be reachable in future runs of the advanced detector. Taken as a whole, these new results improve on previous limits by more than a factor of two.

A high-velocity narrow absorption line outflow in the quasar J212329.46 - 005052.9

Abstract: We report on the discovery of a high-velocity narrow absorption line outflow in the redshift 2.3 quasar J212329.46-005052.9.Five distinct outflow systems are detected with velocity shifts from 9710 to 14,050 km s 1 and Civ ��1548,1551 line widths of FWHM � 62 to 164 km s 1 . This outflow is remarkable for having high speeds and a degree of ionization similar to broad absorption line (BAL) flows, but line widths roughly 100 times narrower than BALs and no apparent X-ray absorption. This is also, to our knowledge, the highest-velocity narrow absorption line system confirmed to be in a quasar outflow by all three indicators of line variability, smooth super-thermal line profiles and doublet ratios that require partial covering of the quasar continuum source. All five systems have stronger absorption in Ovi ��1032,1038 than Civ with no lower ionization metal lines detected. Their line variabilities also appear coordinated, with each system showing larger changes in Civ than Ovi and line strength variations accompanied by nearly commensurate changes in the absorber covering fractions. The metallicity is approximately twice solar. These data require five distinct outflow structures with similar kinematics, physical conditions and characteristic sizes of order 0.01-0.02 pc (based on partial covering). The coordinated line variations, occurring on time scales 60.63 yr (quasar frame), are best explained by global changes in the outflow ionization caused by changes in the quasar’s ionizing flux. An upper limit on the acceleration, .3 km s 1 yr 1 , is consistent with blobs of gas that are gravitationally unbound and coasting freely &5 pc from the central black hole. Additional constraints from the variability time indicate that the full range of plausible distances is 5 . R . 1100 pc. However, if these small absorbing structures were created in the inner flow, they should be near the �5 pc minimum radius because they can travel just a few pc before dissipating (without external confinement). An apparent double line-lock in Civ suggests that the flow was radiatively accelerated and its present trajectory is within �16 o of the radial (line-ofsight) direction. The absence of strong X-ray absorption shows that radiative shielding in the far-UV and X-rays is not needed to maintain moderate BAL-like ionizations and therefore, apparently, it is not needed to facilitate the radiative acceleration to high speeds. We argue that the ionization is moderated, instead, by high gas densities in small outflow sub-structures. Finally, we estimate that the kinetic energy yield from this outflow is at least two orders of magnitude too low to be important for feedback to the host galaxy’s evolution.

Fundamental bound on the reliability of quantum information transmission.

Abstract: Information theory tells us that if the rate of sending information across a noisy channel were above the capacity of that channel, then the transmission would necessarily be unreliable. For classical information sent over classical or quantum channels, one could, under certain conditions, make a stronger statement that the reliability of the transmission shall decay exponentially to zero with the number of channel uses, and the proof of this statement typically relies on a certain fundamental bound on the reliability of the transmission. Such a statement or the bound has never been given for sending quantum information. We give this bound and then use it to give the first example where the reliability of sending quantum information at rates above the capacity decays exponentially to zero. We also show that our framework can be used for proving generalized bounds on the reliability.