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Yong-Shi Wu

Publications and source records attributed to Yong-Shi Wu.

At least 73 records · Page 4Linked to original sources
arXiv2003

Quantum phase transition and engineering in two-component BEC in optical lattices

In this paper we review recent progress in studying quantum phase transitions in one- and two-component Bose-Einstein condensates (BEC) in optical lattices. These phase transitions involve the emergence and disappearance of quantum coherence over whole optical lattice and of linear superposition of macroscopic quantum states. The latter may provide new means to engineer and to manipulate novel macroscopic quantum states and novel coherent atomic beams for quantum information processing, quantum computing etc.

cond-mat.str-el↗
arXiv2002

Quantum phase transition in a multi-component Bose-Einstein condensate in optical lattices

We present the general lattice model for a multi-component atomic Bose-Einstein system in the optical lattice. Using the model, we analytically study the quantum phase transition between Mott insulator and superfluid. A mean-field theory is developed from the Mott insulator ground state. When the inter-species interactions are strong enough, the Mott insulator demonstrates the phase separation behavior. For weak inter-species interactions, the multi species system is miscible. Finally, the phase diagram is discussed with the emphasis on the role of inter-species interactions. The tips of the Mott insulator lobes do not depend on the inter-species interactions, but they indeed modify the range of lobes.

cond-mat.soft↗
arXiv2002

Bosonization and phase Diagram of the one-dimensional t-J model

We present an analytic study of the phase diagram of the one-dimensional t-J model and a couple of its cousins. To deal with the interactions induced by the no double occupancy constraints, we introduce a deformation of the Hubbard operators. When the deformation parameter $Δ$ is small, the induced interactions are softened, accessible by perturbation theory. We combine bososnization with renormalization group techniques to map out the phase diagram of the system. We argue that when $Δ\to 1$, there is no essential change in the phase diagram. Comparison with the existing results in the literature obtained by other methods justifies our deformation approach.

cond-mat.str-el↗
arXiv2001

On Gauge Invariance of Noncommutative Chern-Simons Theories

Motivated by possible applications to condensed matter systems, in this paper we construct U(N) noncommutative Chern-Simons (NCCS) action for a disc and for a double-layer geometry, respectively. In both cases, gauge invariance severely constrains the form of the NCCS action. In the first case, it is necessary to introduce a group-valued boson field with a non-local chiral boundary action, whose gauge variation cancels that of the bulk action. In the second case, the coefficient matrix $K$ in the double U(N) NCCS action is restricted to be of the form with all the matrix elements being the same integer $k$. We suggest that this double NCCS theory with U(1) gauge group describes the so-called Halperin $(kkk)$ state in a double-layer quantum Hall system. Possible physical consequences are addressed.

hep-th↗
arXiv2001

Renormalization Group Equations and the Lifshitz Point In Noncommutative Landau-Ginsburg Theory

A one-loop renormalization group (RG) analysis is performed for noncommutative Landau-Ginsburg theory in an arbitrary dimension. We adopt a modern version of the Wilsonian RG approach, in which a shell integration in momentum space bypasses the potential IR singularities due to UV-IR mixing. The momentum-dependent trigonometric factors in interaction vertices, characteristic of noncommutative geometry, are marginal under RG transformations, and their marginality is preserved at one loop. A negative $Θ$-dependent anomalous dimension is discovered as a novel effect of the UV-IR mixing. We also found a noncommutative Wilson-Fisher (NCWF) fixed point in less than four dimensions. At large noncommutativity, a momentum space instability is induced by quantum fluctuations, and a consequential first-order phase transition is identified together with a Lifshitz point in the phase diagram. In the vicinity of the Lifshitz point, we introduce two critical exponents $ν_m$ and $β_k$, whose values are determined to be 1/4 and 1/2, respectively, at mean-field level.

hep-th↗
arXiv2001

On Critical Phenomena in a Noncommutative Space

In this paper we demonstrate that coordinate noncommutativity at short distances can show up in critical phenomena through UV-IR mixing. In the symmetric phase of the Landau-Ginsburg model, noncommutativity is shown to give rise to a non-zero anomalous dimension at one loop, and to cause instability towards a new phase at large noncommutativity. In particular, in less than four dimensions, the one-loop critical exponent $η$ is non-vanishing at the Wilson-Fisher fixed point.

hep-th↗
arXiv2001

Giant non-linearities accompanying electromagnetically induced transparency

We develop a fully quantum treatment of electromagnetically induced transparency (EIT) in a vapor of three-level $Λ$-type atoms. Both the probe and coupling lasers with arbitrary intensities are quantized, and treated on the same footing. In addition to reproducing known results on ultraslow pulse propagation at the lowest order in the ratio of their Rabi frequencies, our treatment uncovers that the atomic medium with EIT exhibits giant Kerr as well as higher order non-linearities. Enhancement of many orders of magnitude is predicted for higher-order refractive-index coefficients.

quant-ph↗
arXiv2000

One-loop Shift in Noncommutative Chern-Simons Coupling

In this paper we study the one-loop shift in the coupling constant in a noncommutative pure U(N) Chern-Simons gauge theory in three dimensions. The one-loop shift is shown to be a constant proportional to $N$, independent of noncommutativity parameters, and non-vanishing for U(1) theory. Possible physical and mathematical implications of this result are discussed.

hep-th↗
arXiv2000

Comments on Noncommutative Open String Theory: V-duality and Holography

In this paper we study the interplay of electric and magnetic backgrounds in determining the decoupling limit of coincident D-branes towards a noncommutative Yang-Mills (NCYM) or open string (NCOS) theory. No decoupling limit has been found for NCYM with space-time noncommutativity. It is suggested that there is a new duality, which we call V-duality, which acts on NCOS with both space-space and space-time noncommutativity, resulting from decoupling in Lorentz-boost related backgrounds. We also show that the holographic correspondence, previously suggested by Li and Wu, between NCYM and its supergravity dual can be generalized to NCOS as well.

hep-th↗
arXiv2000

The c-Functions of Noncommutative Yang-Mills Theory from Holography

In this paper we study non-commutative Yang-Mills theory (NCYM) through its gravity dual. First it is shown that the gravity dual of an NCYM with self-dual $θ$-parameters has a Lagrangian in the form of five-dimensional dilatonic gravity. Then we use the de-Boer-Verlinde-Verlinde formalism for holographic renormalization group flows to calculate the coefficient functions in the Weyl anomaly of the NCYM at low energies under the assumption of potential dominance, and show that the $C$-theorem holds true in the present case.

hep-th↗
arXiv2000

Characterization of One-Dimensional Luttinger Liquids in Terms of Fractional Exclusion Statistics

We develop a bosonization approach to study the low temperature properties of one-dimensional gas of particles obeying fractional exclusion statistics (FES). It is shown that such ideal gas reproduces the low-energy excitations and asymptotic exponents of a one-component Luttinger liquid (with no internal degrees of freedom). The bosonized effective theory at low energy (or temperature) is identified to a $c=1$ conformal field theory (CFT) with compactified radius determined by the statistics parameter $λ$. Moreover, this CFT can be put into a form of the harmonic fluid description for Luttinger liquids, with the Haldane controlling parameter identified with the statistics parameter (of quasi-particle excitations). Thus we propose to use the latter to characterize the fixed points of 1-d Luttinger liquids. Such a characterization is further shown to be valid for generalized ideal gas of particles with mutual statistics in momentum space and for non-ideal gas with Luttinger-type interactions: In either case, the low temperature behavior is controlled by an effective statistics varying in a fixed-point line.

cond-mat.str-el↗
arXiv1999

Bosonization Based on Bethe Ansatz Equations and Spin-Charge Separation in the Hubbard Model with Finite U

We develop a bosonization approach for one-dimensional models based on Bethe ansatz equations. The operator formalism of the exact soluble models in the low energy limit provides a systematic method to calculate the asymptotic correlation functions. As examples with and without internal degrees of freedom, the Calogero-Sutherland (C-S) model and the repulsive Hubbard model are considered respectively. We verify that the low energy behavior of the C-S model is controlled by two classes of c=1 conformal field theories, depending on whether the C-S interactions are among bosons or among fermions. For the Hubbard model, we show the explicit charge-spin separation at low energy for arbitrary U>0. The low energy behavior of the system is described by the (semi-) direct product of two independent Virasoro algebras with c=1.

cond-mat.str-el↗
arXiv1999

Holography and Noncommutative Yang-Mills

In this note a lately proposed gravity dual of noncommutative Yang-Mills theory is derived from the relations, recently suggested by Seiberg and Witten, between closed string moduli and open string moduli. The only new input one needs is a simple form of the running string tension as a function of energy. This derivation provides convincing evidence that string theory integrates with the holographical principle, and demonstrates a direct link between noncommutative Yang-Mills theory and holography.

hep-th↗
arXiv1999

Does spin-orbit coupling play a role in metal-nonmetal transition in two-dimensional systems?

We propose an experiment, which would allow to pinpoint the role of spin-orbit coupling in the metal-nonmetal transition observed in a number of two-dimensional systems at low densities. Namely, we demonstrate that in a parallel magnetic field the interplay between the spin-orbit coupling and the Zeeman splitting leads to a characteristic anisotropy of resistivity with respect to the direction of the in-plane magnetic field. Though our analytic calculation is done in the deeply insulating regime, the anisotropy is expected to persist far beyond that regime.

cond-mat.mes-hall↗
arXiv1999

Near-Horizon Virasoro Symmetry and the Entropy of de Sitter Space in Any Dimension

De Sitter spacetime is known to have a cosmological horizon that enjoys thermodynamic-like properties similar to those of a black hole horizon. In this note we show that a universal argument can be given for the entropy of de Sitter spacetime in arbitrary dimensions, by generalizing a recent near horizon symmetry plus conformal field theory argument of Carlip for black hole entropy. The implications of this argument are also discussed.

hep-th↗
arXiv1998

Matrix Compactification On Orientifolds

Generalizing previous results for orbifolds, in this paper we describe the compactification of Matrix model on an orientifold which is a quotient space as a Yang-Mills theory living on a quantum space. The information of the compactification is encoded in the action of the discrete symmetry group G on Euclidean space and a projective representation U of G. The choice of Hilbert space on which the algebra of U is realized as an operator algebra corresponds to the choice of a physical background for the compactification. All these data are summarized in the spectral triple of the quantum space.

hep-th↗
arXiv1998

The Schrodinger-like Equation for a Nonrelativistic Electron in a Photon Field of Arbitrary Intensity

The ordinary Schrodinger equation with minimal coupling for a nonrelativistic electron interacting with a single-mode photon field is not satisfied by the nonrelativistic limit of the exact solutions to the corresponding Dirac equation. A Schrodinger-like equation valid for arbitrary photon intensity is derived from the Dirac equation without the weak-field assumption. The "eigenvalue" in the new equation is an operator in a Cartan subalgebra. An approximation consistent with the nonrelativistic energy level derived from its relativistic value replaces the "eigenvalue" operator by an ordinary number, recovering the ordinary Schrodinger eigenvalue equation used in the formal scattering formalism. The Schrodinger-like equation for the multimode case is also presented.

physics.atom-ph↗