arXiv subjects
Publications and source records attributed to Bin Chen.
We study supersymmetric Wilson loop operators in ABJM theory from both sides of the AdS_4/CFT_3 correspondence. We first construct some supersymmetric Wilson loops. The perturbative computations are performed in the field theory side at the first two orders. A fundamental string solution ending on a circular loop is also studied.
Using the methods of general relativity Lindquist derived the radiative transfer equation that is correct to all orders in v/c. Mihalas developed a method of solution for the important case of monotonic velocity fields with spherically symmetry. We have developed the generalized atmosphere code PHOENIX, which in 1-D has used the framework of Mihalas to solve the radiative transfer equation (RTE) in 1-D moving flows. We describe our recent work including 3-D radiation transfer in PHOENIX and particularly including moving flows exactly using a novel affine method. We briefly discuss quantitative spectroscopy in supernovae.
This paper has been withdrawn by the authors due to the paper is far from complishment.
In this paper we investigate the physical implications of the dynamical scalar mode in pure Horava-Lifshitz gravity on cosmology. We find that it can produce a scale-invariant power spectrum in UV era if the detailed balance condition on the action is relaxed. This indicates that the physical scalar mode may seed the large scale structure and Horava-Lifshitz cosmology could be a qualified alternative to inflationary scenario.
We study all tree-level split helicity gluon amplitudes by using the recently proposed BCFW recursion relation and Hodges diagrams in ambitwistor space. We pick out the contributing diagrams and find that all of them can be divided into triangles in a suitable way. We give the explicit expressions for all of these amplitudes. As an example, we reproduce the six gluon split NMHV amplitudes in momentum space.
We show that it is possible to equate the intensity reduction of a light wave caused by weak absorption with a geometrical reduction in intensity caused by a "transverse" conformal transformation of the spacetime metric in which the wave travels. We are consequently able to modify Gordon's optical metric to account for electromagnetic properties of ponderable material whose properties include both refraction and absorption. Unlike refraction alone however, including absorption requires a modification of the optical metric that depends on the eikonal of the wave itself. We derive the distance-redshift relation from the modified optical metric for Friedman-Lemaître-Robertson-Walker spacetimes whose cosmic fluid has associated refraction and absorption coefficients. We then fit the current supernovae data and provide an alternate explanation (other than dark energy) of the apparent acceleration of the universe.
We calculate the scalar quasinormal modes of warped $AdS_3$ black holes analytically. We find that in general they are not in agreement with the prediction of the usual AdS/CFT correspondence. Nevertheless, for the black hole not deviating far from BTZ black hole, the quasinormal frequencies are still well consistent with AdS/CFT correspondence.
Observations and theoretical calculations have shown the importance of non-spherically symmetric structures in supernovae. Thus, the interpretation of observed supernova spectra requires the ability to solve the transfer equation in 3-D moving atmospheres. We present an implementation of the solution of the radiative transfer equation in 3-D homologously expanding atmospheres in spherical coordinates. The implementation is exact to all orders in v/c. We use a new affine method that makes use of the fact that photons travel on straight lines. We compare our results in 3-D for spherically symmetric test problems with high velocity fields and find excellent agreement. Our well-tested 1-D results are based on methods where the momentum directions vary along the characteristic (co-moving momentum directions). Thus, we are able to verify both the analytic framework and its numerical implementation. Additionally, we have been able to test the parallelization over characteristics. Using 512^2 momentum angles we ran the code on 16,384 Opteron processors and achieved excellent scaling. It is now possible to calculate synthetic spectra from realistic 3D hydro simulations. This should open an era of progress in hydro modeling, similar to that that occurred in the 1980s when 1-D models were confronted with synthetic spectra.
In this paper, we discuss the non-Guassianity originated from the $α$-vacuum on the CMB anisotropy. For $α$-vacuum, there exist correlation between points in the acausal two patches of de Sitter spactime. Such kind of correlation can lead to large local form non-Guassianity in $α$-vacuum. For the single field slow-roll inflationary scenario, the spacetime is in a quasi-de Sitter phase during the inflation. We will show that the $α$-vacuum in this case will lead to non-Gaussianity with distinguished feature, of a large local form and a very different shape.
In this article we construct a tiny graviton matrix model for type IIB string theory on a plane-wave background with null dilaton. For the linear null dilaton case, we analyze its vacuum and the excitation spectrum around the vacuum, and discuss the time-dependent fuzzy three-sphere solutions and their evolution. It turns out that at very late time the non-Abelian fuzzy degrees of freedom disappear, which indicates the appearance of perturbative strings.
We study several aspects of generalized Janus configuration, which includes a theta term. We investigate the vacuum structure of the theory and find that unlike the Janus configuration without theta term there is no nontrivial vacuum. We also discuss BPS soliton configuration both by supersymmetry analysis and from energy functional. The half BPS configurations could be realized by introducing transverse (p,q)-strings in original brane configuration corresponding to generalized Janus configuration. It turns out the BPS soliton could be taken as modified dyon. We discuss the solution of half BPS equations for the sharp interface case. Moreover we construct less supersymmetric Janus configuration with theta term.
In this paper, we study the semi-classical strings in AdS_4*CP^3 spacetime. We construct various kinds of string solutions, including the point-like, circular, folded and pulsating strings. For the circular and folded strings, we figure out their field theory dual operators. In particular, we discuss the anomalous dimensions of the corresponding operators from decoupled SU(2)*SU(2) spin chain. We find that in the large angular momentum limit, the field theory and string theory results are in very good agreement up to an interpolating function of coupling constant.
In this paper, we develop a simple method for the reconstruction of the string-inspired dark energy model with the lagrangian $ {\cal L} = -V (ϕ) \sqrt{1 - α' {\nabla}_μ ϕ\nabla^μ ϕ+ β' ϕ\Box ϕ} $ given by Cai et. al., which may allow the equation-of-state parameter cross the cosmological constant boundary $ (w=-1) $. We reconstruct this model in the light of three forms of parametrization for dynamical dark energy.
In this article we study D1-D3 (or $\bar{\textrm{D}3}$) brane systems with generic constant electric and magnetic fluxes in IIB string theory. We work out all possible supersymmetric configurations and find out via T-duality all of them and corresponding supersymmetry conditions could be related to the supersymmetric intersecting D1-D1 pairs. And we do D1-D3 (or $\bar{\textrm{D}3}$) open string quantization for a class of configurations. We find that there are many near massless states in NS sector for near-BPS configurations. Furthermore we calculate open string pair creation rate in generic nonsupersymmetric configurations.
In cellular systems using frequency division duplex, growing Internet services cause unbalance of uplink and downlink traffic, resulting in poor uplink spectrum utilization. Addressing this issue, this paper considers overlaying an ad hoc network onto a cellular uplink network for improving spectrum utilization and spatial reuse efficiency. Transmission capacities of the overlaid networks are analyzed, which are defined as the maximum densities of the ad hoc nodes and mobile users under an outage constraint. Using tools from stochastic geometry, the capacity tradeoff curves for the overlaid networks are shown to be linear. Deploying overlaid networks based on frequency separation is proved to achieve higher network capacities than that based on spatial separation. Furthermore, spatial diversity is shown to enhance network capacities.
In this paper, we study the M-brane description of the Wilson-Polyakov surfaces in six-dimensional (2, 0) field theory at finite temperature. We investigate the membrane solution dual to a straight Wilons-Polyakov surface and compute the interaction potential between two parallel straight strings by using AdS/CFT correspondence. Furthermore we discuss the M5-brane solutions dual to various Wilson-Polyakov surfaces. Finally we obtain an universal result about M5-brane solutions in generic backgrounds.
Recently it has been shown that string gas cosmology, an alternative model of the very early universe which does not involve a period of cosmological inflation, can give rise to an almost scale invariant spectrum of metric perturbations. Here we calculate the non-Gaussianities of the spectrum of cosmological fluctuations in string gas cosmology, and find that these non-Gaussianities depend linearly on the wave number and that their amplitude depends sensitively on the string scale. If the string scale is at the TeV scale, string gas cosmology could lead to observable non-Gaussianities, if it is close to the Planck scale, then the non-Gaussianities on current cosmological scales are negligible.
We construct self-dual string soliton solutions in $AdS_4\times S^7$ spacetime, starting from the covariant equations of motion of M5-brane. We study the properties of the solutions and find that their action are linearized, indicating the BPS nature of the solutions, and they have the same electric and magnetic charge. The straight string soliton solution represents the configuration of the membranes ending on M5-brane with a straight string intersection, and it behaves like the spiky solution in flat spacetime. The spherical string soliton solution, which could be related to the straight one by a conformal transformation, represents the membranes ending on M5-brane with a spherical intersection.