238,881 research outputs found
The late time evolution of Gamma-Ray Bursts: ending hyperaccretion and producing flares
We consider the properties of a hyperaccretion model for gamma-ray bursts
(GRBs) at the late time when the mass supply rate is expected to decrease with
time. We point out that the region in the vicinity of the accretor and the
accretor itself can play an important role in determining the rate and time
behavior of the accretion and ultimately the energy output. Motivated by
numerical simulations and theoretical results, we conjecture that the energy
release can be repeatedly stopped and then restarted by the magnetic flux
accumulated around the accretor. We propose that the episode or episodes when
the accretion resumes correspond to X-ray flares discovered recently in a
number of GRBs.Comment: to appear in MNRAS Letters, revised versio
Effective-Field-Theory Approach to Top-Quark Production and Decay
We discuss new physics in top-quark interactions, using an effective field
theory approach. We consider top-quark decay, single top production, and
top-quark pair production. We identify 15 dimension-six operators that
contribute to these processes, and we compute the deviation from the Standard
Model induced by these operators. The results provide a systematic way of
searching for (or obtaining bounds on) physics beyond the Standard Model.Comment: 24 pages, 12 figures; references added, typos correcte
Scaling in the time-dependent failure of a fiber bundle with local load sharing
We study the scaling behaviors of a time-dependent fiber-bundle model with
local load sharing. Upon approaching the complete failure of the bundle, the
breaking rate of fibers diverges according to ,
where is the lifetime of the bundle, and is a quite
universal scaling exponent. The average lifetime of the bundle scales
with the system size as , where depends on the
distribution of individual fiber as well as the breakdown rule.Comment: 5 pages, 4 eps figures; to appear in Phys. Rev.
FLIC Overlap Fermions
The action of the overlap-Dirac operator on a vector is typically implemented
indirectly through a multi-shift conjugate gradient solver. The compute-time
required depends upon the condition number, , of the matrix that is
used as the overlap kernel. While the Wilson action is typically used as the
overlap kernel, the FLIC (Fat Link Irrelevant Clover) action has an improved
condition number and provides up to a factor of two speedup in evaluating the
overlap action. We summarize recent progress on the use of FLIC overlap
fermions.Comment: Lattice2002(chiral
Individual Microscopic Results Of Bottleneck Experiments
This contribution provides microscopic experimental study of pedestrian
motion in front of the bottleneck, explains the high variance of individual
travel time by the statistical analysis of trajectories. The analysis shows
that this heterogeneity increases with increasing occupancy. Some participants
were able to reach lower travel time due more efficient path selection and more
aggressive behavior within the crowd. Based on this observations, linear model
predicting travel time with respect to the aggressiveness of pedestrian is
proposed.Comment: Submitted to Traffic and Granullar Flow 2015, Springe
- …