Searching for new physics in D0→μ+μ−, e+e−, μ±e∓ at BES and/or the super charm-tau factory

In contrast with B0-B̄0, Bs-B̄s mixing where the standard model (SM) contributions overwhelm that of the new physics beyond standard model (BSM), a measured relatively large D0-D̄0 mixing where the SM contribution is negligible, definitely implies the existence of the new physics BSM. It is natural to consider that the rare decays of D meson might be more sensitive to new physics, and the decay mode D0→μ+μ− could be an ideal area to search for new physics because it is a flavor changing process. In this work we look for a trace of the new physics BSM in the leptonic decays of D0. Concretely we discuss the contributions of unparticle or an extra gauge boson Z′ while imposing the constraints set by fitting the D0-D̄0 mixing data. We find that the long-distance SM effects for D0 →ll̄ still exceed those contributions of the BSM under consideration, but for a double-flavor changing process such as D0→μ±e∓, the new physics contribution would be significant

Flat space compressible fluid as holographic dual of black hole with curved horizon

We consider the fluid dual of ( d + 2)-dimensional vacuum Einstein equation either with or without a cosmological constant. The background solutions admit black hole event horizons and the spatial sections of the horizons are conformally flat. Therefore, a d -dimensional flat Euclidean space E d $${\mathbb{E}}^d$$ is contained in the conformal class of the spatial section of the black hole horizon. A compressible, forced, stationary and viscous fluid system can be constructed on the product (Newtonian) spacetime ℝ × E d $$\mathbb{R}\times {\mathbb{E}}^d$$ as the lowest order fluctuation modes around such black hole background. This construction provides the first example of holographic duality which is beyond the class of bulk/boundary correspondence

New class of rotating perfect fluid black holes in three dimensional gravity

We obtain a new class of rotating black holes for Einstein theory with perfect fluid source in (2+1) dimensions. We conclude that these black hole solutions only depend on the variable of the angular velocity m(r) . Some examples of these black holes are given explicitly. In particular, an unknown static black hole in this special background is obtained. In addition, the general properties including the horizon structure, energy conditions and equation of state, mass, and angular momentum are explained in detail

Exploring the low redshift universe: two parametric models for effective pressure

Astrophysical observations have put unprecedentedly tight constraints on cosmological theories. The Λ CDM model, mathematically simple and fits observational data sets well, is preferred for explaining the behavior of universe. But many basic features of the dark sectors are still unknown, which leaves room for various nonstandard cosmological hypotheses. As the pressure of the cosmological constant dark energy is unvarying, ignoring contributions from radiation and curvature terms at low redshift, the effective pressure keeps constant. In this paper, we propose two parametric models for a non-constant effective pressure in order to study the tiny deviation from Λ CDM at low redshift. We recover our phenomenological models in the scenarios of quintessence and phantom fields, and we explore the behavior of the scalar field and potential. We constrain our model parameters with SNe Ia and BAO observations, and we detect subtle hints of ωde<-1 from the data-fitting results of both models, which indicates possibly a phantom dark energy scenario at present

Two component Higgs-portal dark matter

In this paper, we construct two component dark matter model and revisit fine-tuning, unitarity and vacuum stability problem in this framework. Through Higgs-portal interactions, the additional scalar and vector singlet fields can interact with the SM particles. The parameter space of the model are severely constraint by observed relic density and direct detection experiments. We found that, unlike the SM, the fine-tuning problem is relaxed due to the modified Veltman condition. The vacuum stability problem is addressed, the additional contributions from two DM singlets to the β function make the Higgs quartic coupling <math altimg="si1.gif" xmlns="http://www.w3.org/1998/Math/MathML"><mi>λ</mi><mo stretchy="false">(</mo><mi>μ</mi><mo stretchy="false">)</mo></math> be positive up to Planck scale in some parameter space

The “universal property” of horizon entropy sum of black holes in four dimensional asymptotical (anti-)de-Sitter spacetime background

We present a new “universal property” of entropy, that is the “entropy sum” relation of black holes in four dimensional (anti-)de-Sitter asymptotical background. They depend only on the cosmological constant with the necessary effect of the un-physical “virtual” horizon included in the spacetime where only the cosmological constant, mass of black hole, rotation parameter and Maxwell field exist. When there is more extra matter field in the spacetime, one will find the “entropy sum” is also dependent of the strength of these extra matter field. For both cases, we conclude that the “entropy sum” does not depend on the conserved charges M , Q and J , while it does depend on the property of background spacetime. We will mainly test the “entropy sum” relation in static, stationary black hole and some black hole with extra matter source (scalar hair and higher curvature) in the asymptotical (anti-)de-sitter spacetime background. Besides, we point out a newly found counter example of the mass independence of the ”entropy product” relation in the spacetime with extra scalar hair case, while the “entropy sum” relation still holds. These result are indeed suggestive to some underlying microscopic mechanism. Moreover, the cosmological constant and extra matter field dependence of the “entropy sum” of all horizon seems to reveal that “entropy sum” is more general as it is only related to the background field. For the case of asymptotical flat spacetime without any matter source, we give a note for the Kerr black hole case in appendix. One will find only mass dependence of “entropy sum” appears. It makes us believe that, considering the dependence of “entropy sum”, the mass background field may be regarded as the next order of cosmological constant background field and extra matter field. However, fully explaining the relationship between the “entropy sum” relation and background properties still requires further exploration

Extended phase space thermodynamics for third-order Lovelock black holes in diverse dimensions

Treating the cosmological constant as thermodynamic pressure and its conjugate as thermodynamic volume, we investigate the critical behavior of the third-order Lovelock black holes in diverse dimensions. For black hole horizons with different normalized sectional curvature k=0,±1 , the corresponding critical behaviors differ drastically. For k=0 , there is no critical point in the extended thermodynamic phase space. For k=-1 , there is a single critical point in any dimension d≥7 , and for k=+1 , there is a single critical point in 7 dimensions and two critical points in 8, 9, 10, 11 dimensions. We studied the corresponding phase structures in all possible cases

Spectrum of the charmed and b-flavored mesons in the relativistic potential model

We study the bound states of heavy-light quark-antiquark system in the relativistic potential model, where the potential includes the long-distance confinement term, the short-distance Coulomb term and spin-dependent term. The spectrum of B , B * , D , D * and states with higher orbital quantum numbers are obtained. Compared with previous results predicted in the relativistic potential model, the predictions are improved and extended in this work, more theoretical masses are predicted which can be tested in experiment in the future

Factorization of radiative leptonic decays of B− and D− mesons

In this work, we study the factorization of the radiative leptonic decays of B− and D− mesons, the contributions of the order O(ΛQCD/mQ) are taken into account. The factorization is proved to be valid explicitly at the order O(αsΛQCD/mQ) . The hard kernel is obtained. The numerical results are calculated using the wave-function obtained in relativistic potential model. The O(ΛQCD/mQ) contribution is found to be very important, the correction to the decay amplitudes of B−→γeν¯ is about 20%–30%. For D mesons, the O(ΛQCD/mQ) contributions are more important

Gauss–Bonnet coupling constant as a free thermodynamical variable and the associated criticality

The thermodynamic phase space of Gauss–Bonnet (GB) AdS black holes is extended, taking the inverse of the GB coupling constant as a new thermodynamic pressure PGB . We studied the critical behavior associated with PGB in the extended thermodynamic phase space at fixed cosmological constant and electric charge. The result shows that when the black holes are neutral, the associated critical points can only exist in five dimensional GB-AdS black holes with spherical topology, and the corresponding critical exponents are identical to those for the Van der Waals system. For charged GB-AdS black holes, it is shown that there can be only one critical point in five dimensions (for black holes with either spherical or hyperbolic topologies), which also requires the electric charge to be bounded within some appropriate range; while in d>5 dimensions, there can be up to two different critical points at the same electric charge, and the phase transition can occur only at temperatures which are not in between the two critical values