90,068 research outputs found
Deviation of light curves of gamma-ray burst pulses from standard forms due to the curvature effect of spherical fireballs or uniform jets
As revealed previously, under the assumption that some pulses of gamma-ray
bursts are produced by shocks in spherical fireballs or uniform jets of large
opening angles, there exists a standard decay form of the profile of pulses
arising from very narrow or suddenly dimming local (or intrinsic) pulses due to
the relativistic curvature effect (the Doppler effect over the spherical shell
surface). Profiles of pulses arising from other local pulses were previously
found to possess a reverse S-feature deviation from the standard decay form. We
show in this paper that, in addition to the standard decay form shown in Qin et
al. (2004), there exists a marginal decay curve associated with a local
function pulse with a mono-color radiation. We employ the sample of
Kocevski et al. (2003) to check this prediction and find that the phenomenon of
the reverse S-feature is common, when compared with both the standard decay
form and the marginal decay curve. We accordingly propose to take the marginal
decay curve (whose function is simple) as a criteria to check if an observed
pulse could be taken as a candidate suffered from the curvature effect. We
introduce two quantities and to describe the mentioned deviations
within and beyond the position of the decay phase, respectively. The
values of and of pulses of the sample are calculated, and the
result suggests that for most of these pulses their corresponding local pulses
might contain a long decay time relative to the time scale of the curvature
effect.Comment: 24 pages, 7 figures, 1 table accepted for publication in MNRA
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Privacy-Preserving iVector-Based Speaker Verification
This paper introduces an efficient algorithm to develop a privacy-preserving voice verification based on iVector and linear discriminant analysis techniques. This research considers a scenario in which users enrol their voice biometric to access different services (i.e., banking). Once enrolment is completed, users can verify themselves using their voice print instead of alphanumeric passwords. Since a voice print is unique for everyone, storing it with a third-party server raises several privacy concerns. To address this challenge, this paper proposes a novel technique based on randomization to carry out voice authentication, which allows the user to enrol and verify their voice in the randomized domain. To achieve this, the iVector-based voice verification technique has been redesigned to work on the randomized domain. The proposed algorithm is validated using a well-known speech dataset. The proposed algorithm neither compromises the authentication accuracy nor adds additional complexity due to the randomization operations
Density oscillations in trapped dipolar condensates
We investigated the ground state wave function and free expansion of a
trapped dipolar condensate. We find that dipolar interaction may induce both
biconcave and dumbbell density profiles in, respectively, the pancake- and
cigar-shaped traps. On the parameter plane of the interaction strengths, the
density oscillation occurs only when the interaction parameters fall into
certain isolated areas. The relation between the positions of these areas and
the trap geometry is explored. By studying the free expansion of the condensate
with density oscillation, we show that the density oscillation is detectable
from the time-of-flight image.Comment: 7 pages, 9 figure
Mode-Locked Two-Photon States
The concept of mode locking in laser is applied to a two-photon state with
frequency entanglement. Cavity enhanced parametric down-conversion is found to
produce exactly such a state. The mode-locked two-photon state exhibits a
comb-like correlation function. An unbalanced Hong-Ou-Mandel type
interferometer is used to measure the correlation function. A revival of the
typical interference dip is observed. We will discuss schemes for engineering
of quantum states in time domain.Comment: 4 pages, 5 figure
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