118075838
Temperature dependent transport coefficients in a dynamical holographic QCD model
A bstractWe investigate temperature dependent behavior of various transport coefficients in a dynamical holographical QCD model. We show the nontrivial temperature dependent behavior of the transport coefficients, like bulk viscosity, electric conductivity as well as jet quenching parameter, and it is found that all these quantities reveal information of the phase transition. Furthermore, with introducing higher derivative corrections in 5D gravity, the shear viscosity over entropy density ratio also shows a valley around phase transition, and it is found that the shear viscosity over entropy density ratio times the jet quenching over temperature cubic ratio almost remains as a constant above phase transition, and the value is two times larger than the perturbative result in Phys.Rev.Lett.99.192301(2007).
119971617
Quantum dimension as entanglement entropy in two dimensional conformal field theories
We study the entanglement entropy of excited states in two-dimensional conformal field theories (CFTs). In particular, we consider excited states obtained by acting on a vacuum with primary operators. We show that the entanglement entropy increases by a finite constant amount under its time evolution. Moreover, in rational conformal field theories, we prove that this increase of the (both Renyi and von Neumann) entanglement entropy always coincides with the log of the quantum dimension of the primary operator.
118716317
Note on entanglement temperature for low thermal excited states in higher derivative gravity
A bstractWe investigate the entanglement temperature of a small scale subsystem in low excited states by using holographic method. Especially, we study the entanglement entropy and entanglement temperature in higher derivative gravities which are considered as low thermal excitation of pure AdS gravity. We find that the entanglement entropy are related to the central charges of CFT living on the boundary. The relation between the variance of entanglement entropy and energy of a small scale subsystem has been also obtained. Furthermore, the relation is consistent with the first law-like relation that is proposed by Phys. Rev. Lett. 110 (2013)091602. Finally, we derive the formula of the variance of entanglement entropy in general excited states in gravity background with the Fefferman-Graham coordinates and the entanglement temperature can be figured out in special case.
118364646
Scalar Mesons and glueballs in $Dp-Dq$ hard-wall models
Chao Wang, Song He, Mei Huang, Qi-Shu Yan, and Yi Yang 1 Institute of High Energy Physics, Chinese Academy of Sciences, Beijing, China 2 Theoretical Physics Center for Science Facilities, Chinese Academy of Sciences, Beijing, China 3 Department of Physics, University of Toronto, Toronto, Canada 4 Department of Electrophysics, National Chiao-Tung University, Hsinchu, Taiwan and 5 Physics Division, National Center for Theoretical Sciences, Hsinchu, Taiwan (Dated: February 5, 2009)
119262973
Holographic entanglement entropy in insulator/superconductor transition
A bstractWe investigate the behaviors of entanglement entropy in the holographical insulator/superconductor phase transition. We calculate the holographic entanglement entropy for two kinds of geometry configurations in a completely back-reacted gravitational background describing the insulator/superconductor phase transition. The non-monotonic behavior of the entanglement entropy is found in this system. In the belt geometry case, there exist four phases characterized by the chemical potential and belt width.
118646566
Pseudoscalar glueball in a chiral Lagrangian model with instanton effect
We study the pseudoscalar glueball ground state in a chiral effective Lagrangian model proposed by 't Hooft, motivated by taking into account the instanton effects, which can describe not only the chiral symmetry breaking, but also the solution of U{sub A}(1). We study the parameter space allowed by constraints from vacuum conditions and unitary bounds. By considering two scenarios in the 0{sup ++} sector, we find that parameter space which can accommodate the 0{sup -+} sector is sensitive to the conditions in 0{sup ++} sector. From our analysis, it is found that three {eta} states, i.e. {eta}(1295), {eta}(1405), {eta}(1475), can be the pseudoscalar glueball ground state if we assume that the lightest 0{sup ++} glueball ground state has a mass 1710 (or 1500) MeV. While there will be no 0{sup -+} glueball candidate ground state found in experiments if we assume that the lightest 0{sup ++} glueball ground state has a mass 660 MeV. We also point out the determined instanton density (i.e. the parameter k{sub t}) is consistent with those determined from other methods, e.g. instanton liquid approximation and lattice simulations.
119290604
The amplituhedron from momentum twistor diagrams
A bstractWe propose a new diagrammatic formulation of the all-loop scattering amplitudes/Wilson loops in planar N$$ \mathcal{N} $$ = 4 SYM, dubbed the “momentum-twistor diagrams”. These are on-shell-diagrams obtained by gluing trivalent black and white vertices in momentum twistor space, which, in the reduced diagram case, are known to be related to diagrams in the original twistor space. The new diagrams are manifestly Yangian invariant, and they naturally represent factorization and forward-limit contributions in the all-loop BCFW recursion relations in momentum twistor space, in a fashion that is completely different from those in momentum space. We show how to construct and evaluate momentum-twistor diagrams, and how to use them to obtain tree-level amplitudes and loop-level integrands; in particular the latter involve isolated bubble-structures for loop variables arising from forward limits, or the entangled removal of particles. From each diagram, the generalized “boundary measurement” directly gives the C, D matrices, thus a cell in the amplituhedron associated with the amplitude, and we expect that our diagrammatic representations of the amplitude provide triangulations of the amplituhedron. To demonstrate the computational power of the formalism, we give explicit results for general two-loop integrands, and the cells of the amplituhedron for two-loop MHV amplitudes.
7012367
A COVARIANT ENTROPY BOUND CONJECTURE ON THE DYNAMICAL HORIZON
We propose, as a compelling pattern for the holographic principle, a covariant entropy bound conjecture for more general dynamical horizons. Then we apply our conjecture to ΛCDM cosmological models, where we find that it imposes a novel upper bound, 10-90, on the cosmological constant for our own universe by taking into account the dominant entropy contribution from supermassive black holes, which thus provides an alternative macroscopic perspective for understanding the long-standing cosmological constant problem. As an intriguing implication of this conjecture, we also discuss the possible profound relation between the present cosmological constant, the origin of mass, and the anthropic principle.
119222214
Coarse-graining free theories with gauge symmetries: the linearized case
Discretizations of continuum theories often do not preserve the gauge symmetry content. This occurs in particular for diffeomorphism symmetry in general relativity, which leads to severe difficulties in both canonical and covariant quantization approaches. We discuss here the method of perfect actions, which attempts to restore gauge symmetries by mirroring exactly continuum physics on a lattice via a coarse graining process. Analytical results can only be obtained via a perturbative approach, for which we consider the first step, namely the coarse graining of the linearized theory. The linearized gauge symmetries are exact also in the discretized theory; hence, we develop a formalism to deal with gauge systems. Finally, we provide a discretization of linearized gravity as well as a coarse graining map and show that with this choice the three-dimensional (3D) linearized gravity action is invariant under coarse graining.
54062406
Scattering equations and matrices: from Einstein to Yang-Mills, DBI and NLSM
A bstractThe tree-level S-matrix of Einstein’s theory is known to have a representation as an integral over the moduli space of punctured spheres localized to the solutions of the scattering equations. In this paper we introduce three operations that can be applied on the integrand in order to produce other theories. Starting in d + M dimensions we use dimensional reduction to construct Einstein-Maxwell with gauge group U(1)M . The second operation turns gravitons into gluons and we call it “squeezing”. This gives rise to a formula for all multi-trace mixed amplitudes in Einstein-Yang-Mills. Dimensionally reducing Yang-Mills we find the S-matrix of a special Yang-Mills-Scalar (YMS) theory, and by the squeezing operation we find that of a YMS theory with an additional cubic scalar vertex. A corollary of the YMS formula gives one for a single massless scalar with a ϕ4 interaction. Starting again from Einstein’s theory but in d + d dimensions we introduce a “generalized dimensional reduction” that produces the Born-Infeld theory or a special Galileon theory in d dimensions depending on how it is applied. An extension of Born-Infeld formula leads to one for the Dirac-Born-Infeld (DBI) theory. By applying the same operation to Yang-Mills we obtain the U(N ) non-linear sigma model (NLSM). Finally, we show how the Kawai-Lewellen-Tye relations naturally follow from our formulation and provide additional connections among these theories. One such relation constructs DBI from YMS and NLSM.
5989560
A covariant entropy conjecture on cosmological dynamical horizon
We here propose a covariant entropy conjecture on cosmological dynamical horizon. After the formulation of our conjecture, we test its validity in adiabatically expanding universes with open, flat and closed spatial geometry, where our conjecture can also be viewed as a cosmological version of the generalized second law of thermodynamics in some sense.