16,161 research outputs found
Dual condensates at finite isospin chemical potential
The dual observables as order parameters for center symmetry are tested at
finite isospin chemical potential in a Polyakov-loop enhanced chiral
model of QCD with physical quark masses. As a counterpart of the dressed
Polyakov-loop, the first Fourier moment of pion condensate is introduced for
under the temporal twisted boundary conditions for quarks.
We demonstrate that this dual condensate exhibits the similar temperature
dependence as the conventional Polyakov-loop. We confirm that its rapid
increase with is driven by the evaporating of pion condensation. On the
other hand, the dressed Polyakov-loop shows abnormal thermal behavior, which
even decreases with at low temperatures due to the influence of pion
condensate. We thus argue that in QCD the critical temperature extracting from
a dual observable may have nothing to do with the quark
confinement-deconfinement transition if the quark mass is very small.Comment: 8 pages, 6 figure
Global well-posedness and scattering for the energy-critical, defocusing Hartree equation for radial data
We consider the defocusing, -critical Hartree equation for the
radial data in all dimensions . We show the global well-posedness
and scattering results in the energy space. The new ingredient in this paper is
that we first take advantage of the term in the localized Morawetz
identity to rule out the possibility of energy concentration, instead of the
classical Morawetz estimate dependent of the nonlinearity.Comment: 23 pages, 1 figur
Enhancing the bandwidth of gravitational-wave detectors with unstable optomechanical filters
For gravitational-wave interferometric detectors, there is a tradeoff between
the detector bandwidth and peak sensitivity when focusing on the shot noise
level. This has to do with the frequency-dependent propagation phase lag
(positive dispersion) of the signal. We consider embedding an active unstable
filter---a cavity-assisted optomechanical device operating in the instability
regime---inside the interferometer to compensate the phase, and using feedback
control to stabilize the entire system. We show that this scheme in principle
can enhance the bandwidth without sacrificing the peak sensitivity. However,
there is one practical difficulty for implementing it due to the thermal
fluctuation of the mechanical oscillator in the optomechanical filter, which
puts a very stringent requirement on the environmental temperature and the
mechanical quality factor.Comment: 5 pages and 6 figures. Comments are welcom
Quantum noise of white light cavity using double-pumped gain medium
Laser interferometric gravitational-wave detectors implement Fabry-Perot
cavities to increase their peak sensitivity. However, this is at cost of
reducing their detection bandwidth, which origins from the propagation phase
delay of the light. The "white-light-cavity" idea, first proposed by Wicht et
al. [Optics Communications 134, 431 (1997)], is to circumvent this limitation
by introducing anomalous dispersion, using double-pumped gain medium, to
compensate for such phase delay. In this article, starting from the Hamiltonian
of atom-light interaction, we apply the input-output formalism to evaluate the
quantum noise of the system. We find that apart from the additional noise
associated with the parametric amplification process noticed by others, the
stability condition for the entire system poses an additional constraint.
Through surveying the parameter regimes where the gain medium remains stable
(not lasing) and stationary, we find that there is no net enhancement of the
shot-noise limited sensitivity. Therefore, other gain mediums or different
parameter regimes shall be explored for realizing the white light cavity.Comment: 12 pages, 7 figure
Quantum ground-state cooling and tripartite entanglement with three-mode optoacoustic interactions
We present a quantum analysis of three-mode optoacoustic parametric
interactions in an optical cavity, in which two orthogonal transverse
optical-cavity modes are coupled to one acoustic mode through radiation
pressure. Due to the optimal frequency matching -- the frequency separation of
two cavity modes is equal to the acoustic-mode frequency -- the carrier and
sideband fields simultaneously resonate and coherently build up. This mechanism
significantly enhances the optoacoustic couplings in the quantum regime. It
allows exploration of quantum behavior of optoacoustic interactions in
small-scale table-top experiments. We show explicitly that given an
experimentally achievable parameter, three-mode scheme can realize quantum
ground-state cooling of milligram scale mechanical oscillators and create
robust stationary tripartite optoacoustic quantum entanglements.Comment: 20 pages, 5 figure
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