13,756 research outputs found
A history of the Lonar crater, India: An overview
The origin of the circular structure at Lonar, India, described variously as cauldron, pit, hollow, depression, and crater, has been a controversial subject since the early nineteenth century. A history of its origin and other aspects from 1823 to 1990 are overviewed. The structure in the Deccan Trap Basalt is nearly circular with a breach in the northeast, 1830 m in diameter, 150 m deep, with a saline lake in the crater floor. Over the years, the origin of the Lonar structure has risen from volcanism, subsidence, and cryptovolcanism to an authentic meteorite impact crater. Lonar is unique because it is probably the only terrestrial crater in basalt and is the closest analog with the Moon's craters. Some unresolved questions are suggested. The proposal is made that the young Lonar impact crater, which is less than 50,000 years old, should be considered as the best crater laboratory analogous to those of the Moon, be treated as a global monument, and preserved for scientists to comprehend more about the mysteries of nature and impact cratering, which is now emerging as a fundamental ubiquitous geological process in the evolution of the planets
Phase effects on synchronization by dynamical relaying in delay-coupled systems
Synchronization in an array of mutually coupled systems with a finite
time-delay in coupling is studied using Josephson junction as a model system.
The sum of the transverse Lyapunov exponents is evaluated as a function of the
parameters by linearizing the equation about the synchronization manifold. The
dependence of synchronization on damping parameter, coupling constant and
time-delay is studied numerically. The change in the dynamics of the system due
to time-delay and phase difference between the applied fields is studied. The
case where a small frequency detuning between the applied fields is also
discussed.Comment: 14 pages, 8 figures, Accepted for publication in "CHAOS
Dynamics of coupled Josephson junctions under the influence of applied fields
We investigate the effect of the phase difference of applied fields on the
dynamics of mutually coupled Josephson junction.
The system desynchronizes for any value of applied phase difference and the
dynamics even changes from chaotic to periodic motion for some values of
applied phase difference. We report that by keeping the value of phase
difference as , the system continues to be in periodic motion for a wide
range of system parameter values which might be of great practical
applications.Comment: 13 pages 13 figure
Pre-thermal phases of matter protected by time-translation symmetry
In a periodically driven (Floquet) system, there is the possibility for new
phases of matter, not present in stationary systems, protected by discrete
time-translation symmetry. This includes topological phases protected in part
by time-translation symmetry, as well as phases distinguished by the
spontaneous breaking of this symmetry, dubbed "Floquet time crystals". We show
that such phases of matter can exist in the pre-thermal regime of
periodically-driven systems, which exists generically for sufficiently large
drive frequency, thereby eliminating the need for integrability or strong
quenched disorder that limited previous constructions. We prove a theorem that
states that such a pre-thermal regime persists until times that are nearly
exponentially-long in the ratio of certain couplings to the drive frequency. By
similar techniques, we can also construct stationary systems which
spontaneously break *continuous* time-translation symmetry. We argue
furthermore that for driven systems coupled to a cold bath, the pre-thermal
regime could potentially persist to infinite time.Comment: Published version, with new title and introductio
All tree level scattering amplitudes in Chern-Simons theories with fundamental matter
We show that Britto-Cachazo-Feng-Witten (BCFW) recursion relations can be
used to compute all tree level scattering amplitudes in terms of
scattering amplitude in Chern-Simons
(CS) theory coupled to matter in fundamental representation. As a byproduct, we
also obtain a recursion relation for the CS theory coupled to regular fermions,
even though in this case standard BCFW deformations do not have a good
asymptotic behaviour. Moreover at large , scattering can be
computed exactly to all orders in 't Hooft coupling as was done in earlier
works by some of the authors. In particular, for theory, it
was shown that scattering is tree level exact to all orders
except in the anyonic channel arXiv:1505.06571, where it gets renormalized by a
simple function of 't Hooft coupling. This suggests that it may be possible to
compute the all loop exact result for arbitrary higher point scattering
amplitudes at large .Comment: RevTEX 4.1, 5 pages+6 Appendices, 7 figures; V2 Published versio
Teaching of Critical Analysis of Drug Advertisements to Medical Students
Background: Medical practitioners utilize drug promotional materials from pharmaceutical companies as a major source of information especially in developing countries. These promotional materials can be highly informative as long as they are critically appraised but when they are accepted without question, they lead to irrational prescribing. Aim: To sensitize the students regarding WHO criteria for medicinal drug promotion and to determine the impact of teaching critical appraisal of medicinal drug promotion to medical students. Design: The medical students of second year were given a pre test questionnaire to identify the violations in generic labeling, pharmacological information, claims, relevance and references cited in the drug advertisements. Later they were sensitized about the WHO criteria for medicinal drug promotion and how to critically appraise a drug advertisement. This was followed by a post test questionnaire with the same drug advertisement. Result: The number of students answering the post test correctly was significantly (p<0.05) more than that of pre test. Conclusion: Education of medical students regarding critical analysis of drug advertisements should be a part of the medical curriculum
General relativistic treatment of LISA optical links
LISA is a joint space mission of the NASA and the ESA for detecting low
frequency gravitational waves in the band Hz. In order to attain
the requisite sensitivity for LISA, the laser frequency noise must be
suppressed below the other secondary noises such as the optical path noise,
acceleration noise etc. This is achieved by combining time-delayed data for
which precise knowledge of time-delays is required. The gravitational field,
mainly that of the Sun and the motion of LISA affect the time-delays and the
optical links. Further, the effect of the gravitational field of the Earth on
the orbits of spacecraft is included. This leads to additional flexing over and
above that of the Sun. We have written a numerical code which computes the
optical links, that is, the time-delays with great accuracy
metres - more than what is required for time delay interferometry (TDI) - for
most of the orbit and with sufficient accuracy within metres for an
integrated time window of about six days, when one of the arms tends to be
tangent to the orbit. Our analysis of the optical links is fully general
relativistic and the numerical code takes into account effects such as the
Sagnac, Shapiro delay, etc.. We show that with the deemed parameters in the
design of LISA, there are symmetries inherent in the configuration of LISA and
in the physics, which may be used effectively to suppress the residual laser
noise in the modified first generation TDI. We demonstrate our results for some
important TDI variables
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