895 research outputs found
FFLO correlation and free fluids in the one-dimensional attractive Hubbard model
In this Rapid Communication we show that low energy macroscopic properties of
the one-dimensional (1D) attractive Hubbard model exhibit two fluids of bound
pairs and of unpaired fermions. Using the thermodynamic Bethe ansatz equations
of the model, we first determine the low temperature phase diagram and
analytically calculate the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) pairing
correlation function for the partially-polarized phase. We then show that for
such a FFLO-like state in the low density regime the effective chemical
potentials of bound pairs and unpaired fermions behave like two free fluids.
Consequently, the susceptibility, compressibility and specific heat obey simple
additivity rules, indicating the `free' particle nature of interacting fermions
on a 1D lattice. In contrast to the continuum Fermi gases, the correlation
critical exponents and thermodynamics of the attractive Hubbard model
essentially depend on two lattice interacting parameters. Finally, we study
scaling functions, the Wilson ratio and susceptibility which provide universal
macroscopic properties/dimensionless constants of interacting fermions at low
energy.Comment: In this Letter we analytically study FFLO pairing correlation and the
universal nature of the FFLO-like state. More detailed studies of this model
will be presented in arXiv:1710.08742 and arXiv:1708.0778
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A words-of-interest model of sketch representation for image retrieval
In this paper we propose a method for sketch-based image retrieval. Sketch is a magical medium which is capable of conveying semantic messages for user. It’s in accordance with user’s cognitive psychology to retrieve images with sketch. In order to narrow down the semantic gap between the user and the images in database, we preprocess all the images into sketches by the coherent line drawing algorithm. During the process of sketches extraction, saliency maps are used to filter out the redundant background information, while preserve the important semantic information. We use a variant of Words-of-Interest model to retrieve relevant images for the user according to the query. Words-of-Interest (WoI) model is based on Bag-ofvisual Words (BoW) model, which has been proven successfully for information retrieval. Bag-of-Words ignores the spatial relationships among visual words, which are important for sketch representation. Our method takes advantage of the spatial information of the query to select words of interest. Experimental results demonstrate that our sketch-based retrieval method achieves a good tradeoff between retrieval accuracy and semantic representation of users’ query
Asymptotic correlation functions and FFLO signature for the one-dimensional attractive Hubbard model
We study the long-distance asymptotic behavior of various correlation
functions for the one-dimensional (1D) attractive Hubbard model in a partially
polarized phase through the Bethe ansatz and conformal field theory approaches.
We particularly find the oscillating behavior of these correlation functions
with spatial power-law decay, of which the pair (spin) correlation function
oscillates with a frequency (). Here is the mismatch in the Fermi surfaces of
spin-up and spin-down particles. Consequently, the pair correlation function in
momentum space has peaks at the mismatch , which has been
observed in recent numerical work on this model. These singular peaks in
momentum space together with the spatial oscillation suggest an analog of the
Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state in the 1D Hubbard model. The
parameter representing the lattice effect becomes prominent in critical
exponents which determine the power-law decay of all correlation functions. We
point out that the backscattering of unpaired fermions and bound pairs within
their own Fermi points gives a microscopic origin of the FFLO pairing in 1D.Comment: 26 pages, 4 figures, published version, a series of study on the 1D
attractive Hubbard model, few typos were corrected, references were added,
also see arXiv:1708.07784 and arXiv:1708.0777
Exact results of dynamical structure factor of Lieb-Liniger model
The dynamical structure factor (DSF) represents a measure of dynamical
density-density correlations in a quantum many-body system. Due to the
complexity of many-body correlations and quantum fluctuations in a system of an
infinitely large Hilbert space, such kind of dynamical correlations often
impose a big theoretical challenge. For one dimensional (1D) quantum many-body
systems, qualitative predictions of dynamical response functions are usually
carried out by using the Tomonaga-Luttinger liquid (TLL) theory. In this
scenario, a precise evaluation of the DSF for a 1D quantum system with
arbitrary interaction strength remains a formidable task. In this paper, we use
the form factor approach based on algebraic Bethe ansatz theory to calculate
precisely the DSF of Lieb-Liniger model with an arbitrary interaction strength
at a large scale of particle number. We find that the DSF for a system as large
as 2000 particles enables us to depict precisely its line-shape from which the
power-law singularity with corresponding exponents in the vicinities of
spectral thresholds naturally emerge. It should be noted that, the advantage of
our algorithm promises an access to the threshold behavior of dynamical
correlation functions, further confirming the validity of nonlinear TLL theory
besides Kitanine et. al. 2012 J. Stat. Mech. P09001. Finally we discuss a
comparison of results with the results from the ABACUS method by J.-S. Caux
2009 J. Math. Phys. 50 095214 as well as from the strongly coupling expansion
by Brand and Cherny 2005 Phys. Rev. A 72 033619.Comment: 20 pages, 5 figure
Exact Spectral Function of One-Dimensional Bose Gases
Strong correlation in one-dimensional (1D) quantum systems drastically
changes their dynamic and transport properties in the presence of the
interaction. In this letter, combining quantum integrable theory with numerics,
we exactly compute the spectral function of 1D Lieb-Liniger gas at a many-body
level of large scales. It turns out that a full capture of the power-law
singularities in the vicinities of thresholds requires system size as large as
thousands of particles. Our research essentially confirms the validity of the
nonlinear Tomonaga-Luttinger liquid and provides a reliable technique for
studying critical behaviour emerged only in thermodynamic limit.Comment: 6 pages, 3 figures, Supplementary Materia
Shadow of general rotating black hole
The Johannsen black hole (BH) is a generic rotating BH admitting three
constants of motions ( energy, angular momentum and Carter constant) and is
characterized by four deviation parameters besides mass and spin, which could
be a model-independent probe of the no-hair theorem. We study the effects of
the deviation parameters on the BH shadow as well as the effects of spin. By
using the shadow boundaries of M87* and SgrA*, for the fist time, the deviation
parameters of are constrained. The detail results depend on the spin and
inclination angle . Assuming and , the
deviation parameter are constained within [-3.5, 6] for
M87* observation and [-3, 0.5] for SgrA* observation. We also show the images
of a Johannsen BH surrounded by a Page-Thorne thin accretion disk observed by a
remote observer with a ray-tracing method, and discuss the effects of the
deviation parameters on deforming the accretion disk image, which could be
tested by observations with higher sensitivities in the future.Comment: 14 pages, 9 figure
Poly[[aqua(1-naphthylacetato)cadmium(II)]-μ3-pyridin-3-olato]
In the title complex, [Cd(C5H4NO)(C12H9O2)(H2O)]n, each CdII atom is coordinated by two carboxylate O atoms from one 1-naphthylacetate ligand, two hydroxyl O atoms from two pyridin-3-olate ligands, one N atom from another pyridin-3-olate ligand and one water molecule, and displays a distorted octahedral coordination geometry. The compound forms infinite chains of pyridin-3-olate ligands bridging 1-naphthylacetate–CdII units parallel to the b axis, with a Cd⋯Cd separation of 3.578 (2) Å. The chains are further self-assembled into a supramolecular network through intermolecular O—H⋯O hydrogen-bonding interactions
Tricyclohexyl(3,5-dibromo-2-hydroxybenzoato-κO)tin(IV)
In the title compound, [Sn(C6H11)3(C7H3Br2O3)], the Sn atom is four-coordinate and possesses a distorted Sn(C3O) tetrahedral geometry, with Sn—C bond lengths in the range 2.132 (6)–2.144 (6) Å and with Sn—O = 2.086 (4) Å. The uncoordinated carboxylate O atom forms a weak contact with the Sn atom, with an Sn⋯O separation of 2.962 (2) Å
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