33,037 research outputs found

    Moderate Deviations for the SSEP with a Slow Bond

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    We consider the one dimensional symmetric simple exclusion process with a slow bond. In this model, particles cross each bond at rate N2N^2, except one particular bond, the slow bond, where the rate is NN. Above, NN is the scaling parameter. This model has been considered in the context of hydrodynamic limits, fluctuations and large deviations. We investigate moderate deviations from hydrodynamics and obtain a moderate deviation principle.Comment: 24 page

    Critical magnetic field in holographic superconductor in Gauss-Bonnet gravity with Born-Infeld electrodynamics

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    In the paper using matching method in the probe limit, we investigate some properties of holographic superconductor in Gauss-Bonnet gravity with Born-Infeld electrodynamics . We discuss the effects of the Gauss-Bonnet coupling \a and Born-Infeld parameter bb on the critical temperature and condensate. We find that both of \a and bb make the critical temperature decrease, which implies the condensate harder to form. Moreover we study the magnetic effect on holographic superconductor and obtain that the ratio between the critical magnetic field and the square of the critical temperature increases from zero as the temperature is lowered below the critical value TcT_c, which agrees well with the former results. We also find the critical magnetic field is indeed affected by Gauss-Bonnet coupling, but not by Born-Infeld parameter.Comment: 13 pages, 5 figure

    Manipulation of electronic and magnetic properties of M2_2C (M=Hf, Nb, Sc, Ta, Ti, V, Zr) monolayer by applying mechanical strains

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    Tuning the electronic and magnetic properties of a material through strain engineering is an effective strategy to enhance the performance of electronic and spintronic devices. Recently synthesized two-dimensional transition metal carbides M2_2C (M=Hf, Nb, Sc, Ta, Ti, V, Zr), known as MXenes, has aroused increasingly attentions in nanoelectronic technology due to their unusual properties. In this paper, first-principles calculations based on density functional theory are carried out to investigate the electronic and magnetic properties of M2_2C subjected to biaxial symmetric mechanical strains. At the strain-free state, all these MXenes exhibit no spontaneous magnetism except for Ti2_2C and Zr2_2C which show a magnetic moment of 1.92 and 1.25 ΞΌB\mu_B/unit, respectively. As the tensile strain increases, the magnetic moments of MXenes are greatly enhanced and a transition from nonmagnetism to ferromagnetism is observed for those nonmagnetic MXenes at zero strains. The most distinct transition is found in Hf2_2C, in which the magnetic moment is elevated to 1.5 ΞΌB\mu_B/unit at a strain of 15%. We further show that the magnetic properties of Hf2_2C are attributed to the band shift mainly composed of Hf(5dd) states. This strain-tunable magnetism can be utilized to design future spintronics based on MXenes

    Note on Thermodynamics Method of Black Hole/CFT Correspondence

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    In the paper we further refine the thermodynamics method of black hole/CFT correspondence. We show that one can derive the central charges of different holographic pictures directly from the entropy product S+Sβˆ’S_+S_- if it is mass-independent, for a black hole in the Einstein gravity or the gravity without diffeomorphism anomaly. For a general black hole in the Einstein gravity that admits holographic descriptions, we show that the thermodynamics method and asymptotic symmetry group (ASG) analysis can always give consistent results in the extreme limit. Furthermore, we discuss the relation between black hole thermodynamics and the hidden conformal symmetry. We show that the condition T+A+=Tβˆ’Aβˆ’T_+A_+=T_-A_-, with AΒ±A_\pm being the outer and inner horizon areas, is the necessary, but not sufficient, condition for a black hole to have the hidden conformal symmetry. In particular, for the Einstein(-Maxwell) gravity T+A+=Tβˆ’Aβˆ’T_+A_+=T_-A_- is just the condition T+S+=Tβˆ’Sβˆ’T_+S_+=T_-S_-, with SΒ±S_\pm being the outer and inner horizon entropies, which is the condition for the entropy product S+Sβˆ’S_+S_- being mass-dependent. When there exists the hidden conformal symmetry in the low-frequency scattering off the generic non-extremal black hole, it always leads to the same temperatures of dual CFT as the ones got from the thermodynamics method.Comment: 31 pages, references added, published versio
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