7,638 research outputs found
Effective Action Approach for Preheating
We present a semiclassical non-perturbative approach for calculating the
preheating process at the end of inflation. Our method involves integrating out
the decayed particles within the path integral framework and subsequently
determining world-line instanton solutions in the effective action. This
enables us to obtain the effective action of the inflaton, with its imaginary
part linked to the phenomenon of particle creation driven by coherent inflaton
field oscillations. Additionally, we utilize the Bogoliubov transformation to
investigate the evolution of particle density within the medium after multiple
inflaton oscillations. We apply our approach to various final state particles,
including scalar fields, tachyonic fields, and gauge fields. The
non-perturbative approach provides analytical results for preheating that are
in accord with previous methods.Comment: 22 page
3+1 Dimension Schwinger Pair Production with Quantum Computers
Real-time quantum simulation of quantum field theory in (3+1)D requires large
quantum computing resources. With a few-qubit quantum computer, we develop a
novel algorithm and experimentally study the Schwinger effect, the
electron-positron pair production in a strong electric field, in (3+1)D. The
resource reduction is achieved by treating the electric field as a background
field, working in Fourier space transverse to the electric field direction, and
considering parity symmetry, such that we successfully map the three spatial
dimension problems into one spatial dimension problems. We observe that the
rate of pair production of electrons and positrons is consistent with the
theoretical predication of the Schwinger effect. Our work paves the way towards
exploring quantum simulation of quantum field theory beyond one spatial
dimension.Comment: 7 pages, 2 figures, 7 pages supplemental, 1 figure supplementa
The quantum solvation, adiabatic versus nonadiabatic, and Markovian versus non-Markovian nature of electron transfer rate processes
In this work, we revisit the electron transfer rate theory, with particular
interests in the distinct quantum solvation effect, and the characterizations
of adiabatic/nonadiabatic and Markovian/non-Markovian rate processes. We first
present a full account for the quantum solvation effect on the electron
transfer in Debye solvents, addressed previously in J. Theore. & Comput. Chem.
{\bf 5}, 685 (2006). Distinct reaction mechanisms, including the quantum
solvation-induced transitions from barrier-crossing to tunneling, and from
barrierless to quantum barrier-crossing rate processes, are shown in the fast
modulation or low viscosity regime. This regime is also found in favor of
nonadiabatic rate processes. We further propose to use Kubo's motional
narrowing line shape function to describe the Markovian character of the
reaction. It is found that a non-Markovian rate process is most likely to occur
in a symmetric system in the fast modulation regime, where the electron
transfer is dominant by tunneling due to the Fermi resonance.Comment: 13 pages, 10 figures, submitted to J. Phys. Chem.
Notes on monotone Lindelöf property
summary:We provide a necessary and sufficient condition under which a generalized ordered topological product (GOTP) of two GO-spaces is monotonically Lindelöf
A Pan-Function Model for the Utilization of Bandwidth Improvement and PAPR Reduction
Aiming at the digital quadrature modulation system, a mathematical Pan-function model of the optimized baseband symbol signals with a symbol length of 4T was established in accordance with the minimum out-band energy radiation criterion. The intersymbol interference (ISI), symbol-correlated characteristics, and attenuation factor were introduced to establish the mathematical Pan-function model. The Pan-function was added to the constraints of boundary conditions, energy of a single baseband symbol signal, and constant-envelope conditions. Baseband symbol signals with the optimum efficient spectrum were obtained by introducing Fourier series and minimizing the Pan-function. The characteristics of the spectrum and peak-to-average power ratio (PAPR) of the obtained signals were analyzed and compared with the minimum shift keying (MSK) and quadrature phase-shift keying (QPSK) signals. The obtained signals have the characteristics of a higher spectral roll-off rate, less out-band radiation, and quasi-constant envelope. We simulated the performance of the obtained signals, and the simulation results demonstrate that the method is feasible
Is the late near-infrared bump in short-hard GRB 130603B due to the Li-Paczynski kilonova?
Short-hard gamma-ray bursts (GRBs) are widely believed to be produced by the
merger of two binary compact objects, specifically by two neutron stars or by a
neutron star orbiting a black hole. According to the Li-Paczynski kilonova
model, the merger would launch sub-relativistic ejecta and a
near-infrared/optical transient would then occur, lasting up to days, which is
powered by the radioactive decay of heavy elements synthesized in the ejecta.
The detection of a late bump using the {\em Hubble Space Telescope} ({\em HST})
in the near-infrared afterglow light curve of the short-hard GRB 130603B is
indeed consistent with such a model. However, as shown in this Letter, the
limited {\em HST} near-infrared lightcurve behavior can also be interpreted as
the synchrotron radiation of the external shock driven by a wide mildly
relativistic outflow. In such a scenario, the radio emission is expected to
peak with a flux of Jy, which is detectable for current radio
arrays. Hence, the radio afterglow data can provide complementary evidence on
the nature of the bump in GRB 130603B. It is worth noting that good
spectroscopy during the bump phase in short-hard bursts can test validity of
either model above, analogous to spectroscopy of broad-lined Type Ic supernova
in long-soft GRBs.Comment: 4 pages, 2 figures, published in ApJ Lette
A supra-massive magnetar central engine for short GRB 130603B
We show that the peculiar early optical and in particular X-ray afterglow
emission of the short duration burst GRB 130603B can be explained by continuous
energy injection into the blastwave from a supra-massive magnetar central
engine. The observed energetics and temporal/spectral properties of the late
infrared bump (i.e., the "kilonova") are also found consistent with emission
from the ejecta launched during an NS-NS merger and powered by a magnetar
central engine. The isotropic-equivalent kinetic energies of both the GRB
blastwave and the kilonova are about erg, consistent
with being powered by a near-isotropic magnetar wind. However, this relatively
small value demands that most of the initial rotational energy of the magnetar
is carried away by gravitational wave
radiation. Our results suggest that (i) the progenitor of GRB 130603B would be
a NS-NS binary system, whose merger product would be a supra-massive neutron
star that lasted for about seconds; (ii) the equation-of-state of
nuclear matter would be stiff enough to allow survival of a long-lived
supra-massive neutron star, so that it is promising to detect bright
electromagnetic counterparts of gravitational wave triggers without short GRB
associations in the upcoming Advanced LIGO/Virgo era.Comment: Five pages including 1 Figure, to appear in ApJ
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