12,320 research outputs found
Effective generation of Ising interaction and cluster states in coupled microcavities
We propose a scheme for realizing the Ising spin-spin interaction and atomic
cluster states utilizing trapped atoms in coupled microcavities. It is shown
that the atoms can interact with each other via the exchange of virtual photons
of the cavities. Through suitably tuning the parameters, an effective Ising
spin-spin interaction can be generated in this optical system, which is used to
produce the cluster states. This scheme does not need the preparation of
initial states of atoms and cavity modes, and is insensitive to cavity decay.Comment: 11pages, 2 figures, Revtex
Ground-state fidelity of Luttinger liquids: A wave functional approach
We use a wave functional approach to calculate the fidelity of ground states
in the Luttinger liquid universality class of one-dimensional gapless quantum
many-body systems. The ground-state wave functionals are discussed using both
the Schrodinger (functional differential equation) formulation and a path
integral formulation. The fidelity between Luttinger liquids with Luttinger
parameters K and K' is found to decay exponentially with system size, and to
obey the symmetry F(K,K')=F(1/K,1/K') as a consequence of a duality in the
bosonization description of Luttinger liquids.Comment: 13 pages, IOP single-column format. Sec. 3 expanded with discussion
of short-distance cut-off. Some typos corrected. Ref. 44 in v2 is now
footnote 2 (moved by copy editor). Published versio
Interdimensional degeneracies for a quantum three-body system in D dimensions
A new approach is developed to derive the complete spectrum of exact interdimensional degeneracies for a quantum three-body system in D-dimensions. The new method gives a generalization of previous methods
Prediction of Time-Correlated Leakage Rates of Bolted Flanged Connections by Considering the Maximum Gasket Contact Stress
The leakage rates of bolted flanged connections change with service time due to the gasket contact stress relaxation and degradation of gasket material. The nonuniform distribution of gasket contact stress has significant influence on the leakage behavior of the connections. In order to predict the time-correlated leakage rates accurately, both appropriate approaches to dealing with the gasket residual contact stress and a corresponding time-correlated leakage model of sealing elements are needed. In this paper, an analytical model has been developed to determine the maximum contact stress at gasket outer diameter in consideration of creeps of flanges, bolts and gasket coupled to the axial deformation compatibility equation. The analysis was verified against the finite element numerical simulation considering the nonlinear behavior of gasket and material creep. The analytical results of the maximum contact stress of gasket and its change over time compared well with those obtained by finite element method. A time-correlated leakage model of nonmetallic gasket sealing connections based on the porous medium theory was established, in which the effects of the gasket material degradation and contact stress relaxation on the sealing performance were taken into consideration. Furthermore, a leakage rate prediction method was proposed. Some long-term sealing performance tests were performed on two types of gaskets to obtain the coefficients in the leakage model. The leakage rate prediction method proposed in this paper was also validated against the experimental data presented by other researchers, and the errors between the predicted values and the experimental results were within 18%
Phase diagram of a Bose-Fermi mixture in a one-dimensional optical lattice in terms of fidelity and entanglement
We study the ground-state phase diagram of a Bose-Fermi mixture loaded in a
one-dimensional optical lattice by computing the ground-state fidelity and
quantum entanglement. We find that the fidelity is able to signal quantum phase
transitions between the Luttinger liquid phase, the density-wave phase, and the
phase separation state of the system; and the concurrence can be used to signal
the transition between the density-wave phase and the Ising phase.Comment: 4 pages 3 figure
High-flux X-ray photon emission by a superluminal hybrid electromagnetic mode of intense laser in a plasma waveguide
The feasibility of several novel ultrafast X-ray sources has been demonstrated through the interaction between laser and a micro-structured target. However, the resulting photon flux is still deficient for some applications. Here, we proposed a new method to yield high-flux synchrotron radiation by adopting compact hollow plasma waveguide. We verified the method theoretically and numerically. Linearly polarized laser pulses propagating in the waveguide are mainly converted into the electromagnetic mode HE11 with a superluminal phase speed of 1.02c when the pulse is coupled with the waveguide. The mode fields lead to a strong oscillating force and short oscillation period for energetic electrons, which are accelerated via the longitudinal acceleration mechanism. Then, the short X-ray beam is generated with high yield of 1011-1012. The corresponding photon flux reaches 3.5 × 1021 photons s-1 • 0.1% bandwidth. The high-flux source can be even used for single shot ultrafast imaging or the ultrafast X-ray diffraction and absorption studies
Phase diagram and symmetry breaking of SU(4) spin-orbital chain in a generalized external field
The ground state phases of a one-dimensional SU(4) spin-orbital Hamiltonian
in a generalized external field are studied on the basis of Bethe-ansatz
solution. Introducing three Land\'e factors for spin, orbital and their
products in the SU(4) Zeeman term, we discuss systematically the various
symmetry breaking. The magnetization versus external field are obtained by
solving Bethe-ansatz equations numerically. The phase diagrams corresponding to
distinct residual symmetries are given by means of both numerical and
analytical methods.Comment: Revtex4, 16 pages, 7 figure
Variability-selected low-luminosity active galactic nuclei candidates in the 7 Ms Chandra Deep Field-South
In deep X-ray surveys, active galactic nuclei (AGNs) with a broad range of
luminosities have been identified. However, cosmologically distant
low-luminosity AGN (LLAGN, erg s)
identification still poses a challenge due to significant contamination from
host galaxies. Based on the 7 Ms Chandra Deep Field-South (CDF-S) survey, the
longest timescale ( years) deep X-ray survey to date, we utilize an
X-ray variability selection technique to search for LLAGNs that remain
unidentified among the CDF-S X-ray sources. We find 13 variable sources from
110 unclassified CDF-S X-ray sources. Except for one source which could be an
ultraluminous X-ray source, the variability of the remaining 12 sources is most
likely due to accreting supermassive black holes. These 12 AGN candidates have
low intrinsic X-ray luminosities, with a median value of erg
s. They are generally not heavily obscured, with an average effective
power-law photon index of 1.8. The fraction of variable AGNs in the CDF-S is
independent of X-ray luminosity and is only restricted by the total number of
observed net counts, confirming previous findings that X-ray variability is a
near-ubiquitous property of AGNs over a wide range of luminosities. There is an
anti-correlation between X-ray luminosity and variability amplitude for
high-luminosity AGNs, but as the luminosity drops to erg
s, the variability amplitude no longer appears dependent on the
luminosity. The entire observed luminosity-variability trend can be roughly
reproduced by an empirical AGN variability model based on a broken power-law
power spectral density function.Comment: 18 pages, 11 figures, accepted for publication in Ap
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