16941003
From N M2's to N D2's
In this short note, we reduce the N=6, U(N)xU(N) Chern-Simons gauge theories to N=8, U(N) Yang-Mills gauge theories. This process corresponds to recovering the world-volume theory of N D2-branes from that of N M2-branes in an intermediate energy range. The supersymmetries are enhanced because in this limit the branes localize far away from the orbifold singularity. Our main scheme is exactly in accordance with Mukhi and Papageorgakis's earlier work, although the Higgs mechanism becomes trickier in the present case. We also speculate on applying the scheme to a large class of new Bagger-Lambert models more generally.
119201058
Cosmic steps in modeling dark energy
Past and recent data analyses gave some hints of steps in dark energy. Considering dark energy as a dynamical scalar field, we investigate several models with various steps: a step in the scalar potential, a step in the kinetic term, a step in the energy density, and a step in the equation-of-state parameter $w$. These toy models provide a workable mechanism to generate steps and features of dark energy. Remarkably, a single real scalar can cross $w=\ensuremath{-}1$ dynamically with a step in the kinetic term.
6958260
Probing Alpha-Vacua of Black Holes in LHC
Motivated by the idea of alpha-vacua in Schwarzschild spacetime, we studied the deformed spectrum of Hawking radiation. Such a deformation would leave signatures on the small black hole evaporation in LHC because their vacuum deviates from the Unruh state.
119285801
Modified entropic gravity revisited
Inspired by Verlinde’s idea, some modified versions of entropic gravity have been suggested. Extending them in a unified formalism, herein we derive the generalized gravitational equations accordingly. From gravitational equations, the energy-momentum conservation law and cosmological equations are investigated. The covariant conservation law of energy-momentum tensor severely constrains viable modifications of entropic gravity. A discrepancy arises when two independent methods are applied to the homogeneous isotropic universe, posing a serious challenge to modified models of entropic gravity.
119181798
Radiative E1 decays of X(3872)
Abstract Radiative E1 decay widths of X ( 3872 ) are calculated through the relativistic Salpeter method, with the assumption that X ( 3872 ) is the χ c 1 ( 2 P ) state, which is the radial excited state of χ c 1 ( 1 P ) . We first calculated the E1 decay width of χ c 1 ( 1 P ) . The result is in agreement with experimental data excellently. Then we calculated the width of X ( 3872 ) with the assignment χ c 1 ( 2 P ) . Results are: Γ ( X ( 3872 ) → γ J / ψ ) = 33.0 keV , Γ ( X ( 3872 ) → γ ψ ( 2 S ) ) = 146 keV and Γ ( X ( 3872 ) → γ ψ ( 3770 ) ) = 7.09 keV . The ratio Br ( X ( 3872 ) → γ ψ ( 2 S ) ) / Br ( X ( 3872 ) → γ J / ψ ) = 4.4 agrees with experimental data by BaBar, but is larger than the new up-bound reported by Belle recently. With the same method, we also predicted the decay widths, Γ ( χ b 1 ( 1 P ) ) → γ ϒ ( 1 S ) = 30.0 keV , Γ ( χ b 1 ( 2 P ) ) → γ ϒ ( 1 S ) = 5.65 keV and Γ ( χ b 1 ( 2 P ) ) → γ ϒ ( 2 S ) = 15.8 keV , from which we get the full widths: Γ ( χ b 1 ( 1 P ) ) ∼ 85.7 keV and Γ ( χ b 1 ( 2 P ) ) ∼ 66.5 keV .
14951502
GOODS-HERSCHEL: STAR FORMATION, DUST ATTENUATION, AND THE FIR–RADIO CORRELATION ON THE MAIN SEQUENCE OF STAR-FORMING GALAXIES UP TO z ≃ 4*
We use the deep panchromatic dataset available in the GOODS-N field, spanning all the way from GALEX ultra-violet to VLA radio continuum data, to select a star-forming galaxy sample at z~[0.5-4] and robustly measure galaxy photometric redshifts, star formation rates, stellar masses and UV rest-frame properties. We quantitatively explore, using mass-complete samples, the evolution of the star formation activity and dust attenuation properties of star-forming galaxies up to z~4. Our main results can be summarized as follows: i) we find that the slope of the SFR-M correlation is consistent with being constant, and equal to ~0.8 at least up to z~1.5, while the normalization keeps increasing to the highest redshift, z~4, we are able to explore; ii) for the first time in this work, we are able to explore the FIR-radio correlation for a mass-selected sample of star-forming galaxies: the correlation does not evolve up to z~4; iii) we confirm that galaxy stellar mass is a robust proxy for UV dust attenuation in star-forming galaxies, with more massive galaxies being more dust attenuated; iv) strikingly, we find that this attenuation relation evolves very weakly with redshift, the amount of dust attenuation increasing by less than 0.3 magnitudes over the redshift range [0.5-4] for a fixed stellar mass, as opposed to a tenfold increase of star formation rate; v) this finding explains the evolution of the SFR-Auv relation reported in literature: the same amount of star formation is less attenuated at higher redshift because it is hosted in less massive, and less metal rich, galaxies; vi) the correlation between dust attenuation and the UV spectral slope evolves in redshift, with the median UV spectral slope of star-forming galaxies becoming bluer with redshift. By z~3, typical UV slopes are inconsistent, given the measured dust attenuation, with the predictions of commonly used empirical laws: this means that the present cosmic star formation rate density 
estimates at redshift z > 3 need to be increased by a factor of around 2. Finally, building on the measured AUV–logM correlation and on existing results, we find evidence that line reddening is marginally larger (by a factor of around 1.3) than continuum reddening at all redshifts probed, and also that the amount of dust attenuation at a fixed ISM metallicity increases with redshift. We speculate that our results point toward an evolution of the ISM conditions of the median star-forming galaxy, such that at z >1.5, Main Sequence galaxies have ISM properties more similar to those found in local starbursts.
117382818
The Study of Rare $B_c\rightarrow D^{(*)}_{s,d}l\bar{l}$ Decays
In this paper, we study rare decays $B_c\rightarrow D^{(*)}_{s,d}l\bar{l}$ within the Standard Model. The penguin, box, annihilation, color-favored cascade and color-suppressed cascade contributions are included. Based on our calculation, the annihilation and color-favored cascade diagrams play important roles in the differential branching fractions, forward-backward asymmetries, longitudinal polarizations of the final vector mesons and leptonic longitudinal polarization asymmetries. More importantly, color-favored cascade decays largely enhance the resonance cascade contributions. To avoid the resonance cascade contribution pollution, new cutting regions are put forward.
119300428
Why X(3915) is so narrow as a $\chi_{c0}(2P)$ state
New resonance X(3915) was identified as the charmonium $\chi_{c0}(2P)$ by BABAR Collaboration, but there seems still open question of this assignment: why its full width is so narrow? To answer this question, we calculate the Okubo-Zweig-Iizuka (OZI) allowed strong decays $X(3915)\to D \bar D$, where X(3915) is assigned as a $\chi_{c0}(2P)$ state, and estimate its full width in the cooperating framework of $^3/!P_0^{}$ model and the Bethe-Salpeter (BS) method using the Mandelstam Formalism, during which non-perturbative QCD effects of the hadronic matrix elements are well considered by overlapping integral over the relativistic Salpeter wave functions of the initial and finial states. We find the node structure of $\chi_{c0}(2P)$ wave function resulting in the narrow width of X(3915) and show the dependence of the decay width on the variation of the initial mass of X(3915). We point out that the rate of $\frac{\Gamma(X(3915)\to D^+ D^-)}{\Gamma(X(3915)\to D^0 \bar D^0)}$ is crucial to confirm whether X(3915) is the $\chi_{c0}(2P)$ state or not.
123145784
OZI-ALLOWED TWO BODY ϒ DECAYS IN THE 3P0 MODEL WITH THE RELATIVISTIC WAVE FUNCTIONS
We combine the Bethe–Salpeter method with the 3P0 model to describe OZI-allowed two body meson decays. In this combined method, the relativistic wave functions defined in the Salpeter equation show up in the decay amplitude of the 3P0 model automatically. We apply the method to OZI-allowed ϒ(4S, 5S, 6S) two body decays. The results are roughly consistent with the experimental data and the predictions of ϒ(6S) decays are given.