15148390
Study of Hadron Scattering Using an Asymmetric Box
jbzhang@zimp.zju.edu.cnWe propose to study hadron-hadron scattering using lattice QCD in an asymmetric box whichallows one to access more non-degenerate low-momentum modes for a given volume. The con-ventional Luscher’s formula applicable in a symmetric box is modiﬁed accordingly. To illustratethe feasibility of this approach, pion-pion elastic scattering phase shifts in the
13895100
C, P, and T of braid excitations in quantum gravity
Abstract We study the discrete transformations of four-valent braid excitations of framed spin networks embedded in a topological three-manifold. We show that four-valent braids allow seven and only seven discrete transformations. These transformations can be uniquely mapped to C, P, T, and their products. Each CPT multiplet of actively-interacting braids is found to be uniquely characterized by a non-negative integer. Finally, braid interactions turn out to be invariant under C, P, and T.
16635057
The covariant entropy conjecture and concordance cosmological models
Recently a covariant entropy conjecture has been proposed for dynamical horizons. We apply this conjecture to concordance cosmological models, namely, those cosmological models filled with perfect fluids, in the presence of a positive cosmological constant. As a result, we find that this conjecture has a severe constraint power. Not only does this conjecture rule out those cosmological models disfavored by the anthropic principle, but also it imposes an upper bound 10?60 on the cosmological constant for our own universe, which thus provides an alternative macroscopic perspective for understanding the long-standing cosmological constant problem.
517518
New relations for three-dimensional supersymmetric scattering amplitudes.
We provide evidence for a duality between color and kinematics in three-dimensional supersymmetric Chern-Simons matter theories. We show that the six-point amplitude in the maximally supersymmetric N=8 theory can be arranged so that the kinematic factors satisfy the fundamental identity of three-algebras. We further show that the four- and six-point N=8 amplitudes can be squared into the amplitudes of N=16 three-dimensional supergravity, thus providing evidence for a hidden three-algebra structure in the dynamics of the supergravity.
118969895
The Kinematics of particles moving in rainbow spacetime
The kinematics of massive particles moving in rainbow spacetime is studied. We derive the equation of geodesics when the semiclassical effect of moving particles on the background is taken into account. In particular we show that in rainbow flat spacetime the trajectory of a freely falling particle remains unchanged which is still a straight line in energy-independent coordinate system. The implication to the Unruh effect in rainbow flat spacetime is also discussed.
119227620
Scattering in three dimensions from rational maps
A bstractThe complete tree-level S-matrix of four dimensional $ \mathcal{N}=4 $ super Yang-Mills and $ \mathcal{N}=8 $ supergravity has compact forms as integrals over the moduli space of certain rational maps. In this note we derive formulas for amplitudes in three dimensions by using the fact that when amplitudes are dressed with proper wave functions dimensional reduction becomes straightforward. This procedure leads to formulas in terms of rational maps for three dimensional maximally supersymmetric Yang-Mills and gravity theories. The integrand of the new formulas contains three basic structures: Parke-Taylor-like factors, Vandermonde determinants and resultants. Integrating out some of the Grassmann directions produces formulas for theories with less than maximal supersymmetry, which exposes yet a fourth kind of structure. Combining all four basic structures we start a search for consistent S-matrices in three dimensions. Very nicely, the most natural ones are those corresponding to ABJM and BLG theories. We also make a connection between the power of a resultant in the integrand, representations of the Poincaré group, infrared behavior and conformality of a theory. Extensions to other theories in three dimensions and to arbitrary dimensions are also discussed.
118348723
Some aspects of QGP phase in a hQCD model
A bstractWe continue to study the holographic QCD (hQCD) model, proposed in a previous paper, in an Einstein-Maxwell-Dilaton (EMD) system. In this paper we discuss some aspects of quark gluon plasma (QGP) in the hQCD model, such as drag force, jet quenching parameter and screening length. The results turn out to be consistent with those as expected in QCD qualitatively. By calculating free energy of the background black hole solution, we find that there exists a phase transition between small black hole and large black hole when chemical potential μ is less than the critical one μc, and the phase transition is absent when chemical potential is beyond the critical one.
118493750
Massive superstring scatterings in the Regge regime
We calculate four classes of high-energy massive string scattering amplitudes of fermionic string theory at arbitrary mass levels in the Regge regime (RR). We show that all four leading order amplitudes in the RR can be expressed in terms of the Kummer function of the second kind. Based on the summation algorithm of a set of extended signed Stirling number identities, we show that all four ratios calculated previously by the method of decoupling of zero-norm states among scattering amplitudes in the Gross regime can be extracted from this Kummer function in the RR. Finally, we conjecture and give evidence that the existence of these four Gross regime ratios in the RR persists to subleading orders in the Regge expansion of all high-energy fermionic string scattering amplitudes.
76649422
A hQCD model and its phase diagram in Einstein-Maxwell-Dilaton system
A bstractBy use of the potential reconstruction approach we obtain a series of asymptotically AdS (aAdS) black hole solutions in an Einstein-Maxwell-Dilaton (EMD) system. Basing on the solutions of the system, we reconstruct a semi-analytical holographic QCD (hQCD) model with a quadratic term in warped factor. We discuss some aspects of the hQCD model, in particular we calculate the free energy of two static color sources (a heavy quark-antiquark pair) which is an important order parameter to describe confinement/deconfinement phase transition. The behavior of the free energy with respect to temperature and chemical potential is studied. We find that in the hQCD model the deconfinement phase transition can be realized and a critical point occurs. The resulting phase diagram in the temperature-chemical potential T − μ plane is in quite good agreement with the one from recent lattice results and effective models of QCD.
120206017
Heavy Quark Potential and QCD Beta Function from a Deformed AdS5 Model
We show that in a deformed ${\rm AdS}_5$ model with an explicit infrared cutoff included in the logarithmic correction $-c_0\log[(z_{IR}-z)/z_{IR}]$, the heavy quark Cornell potential can be fitted very well, the corresponding beta-function agrees with the QCD beta-function at 2-loop level reasonably well, and its dual dilaton potential is bounded from below in infrared. The results are compared with those in the Andreev-Zakharov model and the Pirner-Galow model.
56229424
Phase structure in a dynamical soft-wall holographic QCD model
A bstractWe consider the Einstein-Maxwell-dilaton system with an arbitrary kinetic gauge function and a dilaton potential. A family of analytic solutions is obtained by the potential reconstruction method. We then study its holographic dual QCD model. The kinetic gauge function can be fixed by requesting the linear Regge spectrum of mesons. We calculate the free energy to obtain the phase diagram of the holographic QCD model and interpret our result as the heavy quarks system by comparing the recent lattice QCD simulation. We finally obtain the equations of state in our model.