9,629 research outputs found
Nuclear quantum shape-phase transitions in odd-mass systems
Microscopic signatures of nuclear ground-state shape phase transitions in
odd-mass Eu isotopes are explored starting from excitation spectra and
collective wave functions obtained by diagonalization of a core-quasiparticle
coupling Hamiltonian based on energy density functionals. As functions of the
physical control parameter -- the number of nucleons -- theoretical low-energy
spectra, two-neutron separation energies, charge isotope shifts, spectroscopic
quadrupole moments, and reduced transition matrix elements accurately
reproduce available data, and exhibit more pronounced discontinuities at
neutron number , compared to the adjacent even-even Sm and Gd isotopes.
The enhancement of the first-order quantum phase transition in odd-mass systems
can be attributed to a shape polarization effect of the unpaired proton which,
at the critical neutron number, starts predominantly coupling to Gd core nuclei
that are characterized by larger quadrupole deformation and weaker proton
pairing correlations compared to the corresponding Sm isotopes.Comment: 6 pages, 4 figure
Mesoscopic circuits with charge discreteness:quantum transmission lines
We propose a quantum Hamiltonian for a transmission line with charge
discreteness. The periodic line is composed of an inductance and a capacitance
per cell. In every cell the charge operator satisfies a nonlinear equation of
motion because of the discreteness of the charge. In the basis of one-energy
per site, the spectrum can be calculated explicitly. We consider briefly the
incorporation of electrical resistance in the line.Comment: 11 pages. 0 figures. Will be published in Phys.Rev.
Mixed-state fidelity and quantum criticality at finite temperature
We extend to finite temperature the fidelity approach to quantum phase
transitions (QPTs). This is done by resorting to the notion of mixed-state
fidelity that allows one to compare two density matrices corresponding to two
different thermal states. By exploiting the same concept we also propose a
finite-temperature generalization of the Loschmidt echo. Explicit analytical
expressions of these quantities are given for a class of quasi-free fermionic
Hamiltonians. A numerical analysis is performed as well showing that the
associated QPTs show their signatures in a finite range of temperatures.Comment: 7 pages, 4 figure
Constraints on Holographic Dark Energy from Latest Supernovae, Galaxy Clustering, and Cosmic Microwave Background Anisotropy Observations
The holographic dark energy model is proposed by Li as an attempt for probing
the nature of dark energy within the framework of quantum gravity. The main
characteristic of holographic dark energy is governed by a numerical parameter
in the model. The parameter can only be determined by observations.
Thus, in order to characterize the evolving feature of dark energy and to
predict the fate of the universe, it is of extraordinary importance to
constrain the parameter by using the currently available observational
data. In this paper, we derive constraints on the holographic dark energy model
from the latest observational data including the gold sample of 182 Type Ia
supernovae (SNIa), the shift parameter of the cosmic microwave background (CMB)
given by the three-year {\it Wilkinson Microwave Anisotropy Probe} ({\it WMAP})
observations, and the baryon acoustic oscillation (BAO) measurement from the
Sloan Digital Sky Survey (SDSS). The joint analysis gives the fit results in
1-: and . That
is to say, though the possibility of is more favored, the possibility of
can not be excluded in one-sigma error range, which is somewhat different
from the result derived from previous investigations using earlier data. So,
according to the new data, the evidence for the quintom feature in the
holographic dark energy model is not as strong as before.Comment: 22 pages, 8 figures; accepted for publication in Phys. Rev.
Spatial organization and evolutional period of the epidemic model using cellular automata
We investigate epidemic models with spatial structure based on the cellular
automata method. The construction of the cellular automata is from the study by
Weimar and Boon about the reaction-diffusion equations [Phys. Rev. E 49, 1749
(1994)]. Our results show that the spatial epidemic models exhibit the
spontaneous formation of irregular spiral waves at large scales within the
domain of chaos. Moreover, the irregular spiral waves grow stably. The system
also shows a spatial period-2 structure at one dimension outside the domain of
chaos. It is interesting that the spatial period-2 structure will break and
transform into a spatial synchronous configuration in the domain of chaos. Our
results confirm that populations embed and disperse more stably in space than
they do in nonspatial counterparts.Comment: 6 papges,5 figures. published in Physics Review
Quenched Charmed Meson Spectra using Tadpole Improved Quark Action on Anisotropic Lattices
Charmed meson charmonium spectra are studied with improved quark actions on
anisotropic lattices. We measured the pseudo-scalar and vector meson dispersion
relations for 4 lowest lattice momentum modes with quark mass values ranging
from the strange quark to charm quark with 3 different values of gauge coupling
and 4 different values of bare speed of light . With the bare
speed of light parameter tuned in a mass-dependent way, we study the mass
spectra of , , ,
, and mesons.
The results extrapolated to the continuum limit are compared with the
experiment and qualitative agreement is found.Comment: 8 pages, 2 figures, latex fil
Sensitive Chemical Compass Assisted by Quantum Criticality
The radical-pair-based chemical reaction could be used by birds for the
navigation via the geomagnetic direction. An inherent physical mechanism is
that the quantum coherent transition from a singlet state to triplet states of
the radical pair could response to the weak magnetic field and be sensitive to
the direction of such a field and then results in different photopigments in
the avian eyes to be sensed. Here, we propose a quantum bionic setup for the
ultra-sensitive probe of a weak magnetic field based on the quantum phase
transition of the environments of the two electrons in the radical pair. We
prove that the yield of the chemical products via the recombination from the
singlet state is determined by the Loschmidt echo of the environments with
interacting nuclear spins. Thus quantum criticality of environments could
enhance the sensitivity of the detection of the weak magnetic field.Comment: 4 pages, 3 figure
Testing quantum adiabaticity with quench echo
Adiabaticity of quantum evolution is important in many settings. One example
is the adiabatic quantum computation. Nevertheless, up to now, there is no
effective method to test the adiabaticity of the evolution when the
eigenenergies of the driven Hamiltonian are not known. We propose a simple
method to check adiabaticity of a quantum process for an arbitrary quantum
system. We further propose a operational method for finding a uniformly
adiabatic quench scheme based on Kibble-Zurek mechanism for the case when the
initial and the final Hamiltonians are given. This method should help in
implementing adiabatic quantum computation.Comment: This is a new version. Some typos in the New Journal of Physics
version have been correcte
Remarks on Hawking radiation as tunneling from the BTZ black holes
Hawking radiation viewed as a semiclassical tunneling process from the event
horizon of the (2 + 1)-dimensional rotating BTZ black hole is carefully
reexamined by taking into account not only the energy conservation but also the
conservation of angular momentum when the effect of the emitted particle's
self-gravitation is incorporated. In contrast to previous analysis of this
issue in the literature, our result obtained here fits well to the
Kraus-Parikh-Wilczek's universal conclusion without any modification to the
Bekenstein-Hawking area-entropy formulae of the BTZ black hole.Comment: 12pages, no figure, use JHEP3.cls. Version better than published one
in JHE
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