119290202
Model building in AdS/CMT: DC Conductivity and Hall angle
Using the bottom-up approach in a holographic setting, we attempt to study both the transport and thermodynamic properties of a generic system in 3+1 dimensional bulk spacetime. We show the exact 1/T and $T^2$ dependence of the longitudinal conductivity and Hall angle, as seen experimentally in most copper-oxide systems, which are believed to be close to quantum critical point. This particular temperature dependence to conductivities are possible in two different cases: (1) Background solutions with scale invariant and broken rotational symmetry, (2) solutions with pseudo-scaling and unbroken rotational symmetry but only at low density limit. Generically, the study of the transport properties in a scale invariant background solution, using the probe brane approach, at high density and at low temperature limit suggests us to consider only metrics with two exponents. More precisely, the spatial part of the metric components should not be same i.e., $g_{xx}\neq g_{yy}$. In doing so, we have generated the above mentioned behavior to conductivity with a very special behavior to specific heat which at low temperature goes as: $C_V\sim T^3$. However, if we break the scaling symmetry of the background solution by including a nontrivial dilaton, axion or both and keep the rotational symmetry then also we can generate such a behavior to conductivity but only in the low density regime. As far as we are aware, this particular temperature dependence to both the conductivity and Hall angle is being shown for the first time using holography.
15867017
NONSINGULAR COSMOLOGIES FROM BRANES
We analyze possible cosmological scenarios on a brane where the brane acts as a dynamical boundary of various black holes with anti-de Sitter or de Sitter asymptotic. In many cases, the brane is found to describe the completely nonsingular universe. In some cases, quantum gravity era of the brane-universe can also be avoided by properly tuning bulk parameters. We further discuss the creation of a brane-universe by studying its wave function. This is done by employing Wheeler–De Witt equation in the mini superspace formalism.
13048896
A new Ricci-flat geometry
Abstract We are proposing a new Ricci-flat metric constructed from an infinite family of Sasaki–Einstein, Y ( p , q ) , geometries. This geometry contains a free parameter s and in the s → 0 limit we get back the usual CY. When this geometry is probed both by a stack of D3 and fractional D3 branes then the corresponding supergravity solution is found which is a warped product of this new 6-dimensional geometry and the flat R 3 , 1 . This solution in the specific limit as mentioned above reproduces the solution found in hep-th/0412193 . The integrated five-form field strength over S 2 × S 3 goes logarithmically but the argument of Log function is different than has been found before.
118477119
eta/s at finite coupling
We compute the ratio of the coefficient of shear viscosity to entropy density at finite coupling and at zero chemical potential using holographic duality, up to ten derivative terms in the low energy effective five-dimensional action, of a specific kind, which may or may not be connected to the supersymmetric completion of type IIB theory. The result suggests that this ratio can be positive only for the 8th derivative term even with the form of that term in the action as C{sup ij}{sub kl}C{sup kl}{sub mn}C{sup mn}{sub rs}C{sup rs}{sub ij}, where C is the Weyl tensor.
119087207
SOLUTION TO WORLDVOLUME ACTION OF D3 BRANE IN pp-WAVE BACKGROUND
We find nonsupersymmetric and supersymmetric solutions of D3 brane configuration in the background of pp-wave obtained as a Penrose limit of AdS5 × S5.
14651966
Supersymmetric and nonsupersymmetric perturbations to KT
We studied the supersymmetric and non-supersymmetric perturbations to cascading gauge theory. In particular we use KT background and the back reaction of the generic linearized perturbation make the dilaton to run and the $T^{(1,1)}$ gets squashed which in turn make the supersymmetry to be broken. But if we make a special linearized perturbation in such way that the $T^{(1,1)}$ is not squashed then the corresponding perturbation preserve supersymmetry.
119271689
Event-plane correlators
Introduction.−High-energy heavy-ion collision experiments at the Relativistic Heavy-Ion Collider (RHIC), BNL and the Large Hadron Collider (LHC), CERN have firmly established the formation of strongly interacting matter which exhibits a strong collective flow [1–3]. This not only suggests that the matter formed is close to local thermal equilibrium but also provides a window to the initial state of the fireball immediately after the collision. Collective flow in the plane transverse to the beam axis is typically measured in terms of two-particle angular correlations [4–7] and its small anisotropies captured in its Fourier harmonics [8–11]. Recently, a new tool, namely correlations among event planes corresponding to different harmonics [12–14], is emerging with a promise to throw additional light on the initial-state phenomena. Pair correlations (i.e., the single-particle anisotropic flow vn extracted from two-particle correlations) are reasonably well understood [8]. Event-plane correlators represent higher-order correlations, involving at least three particles. Such higher-order correlations thus open a new direction in heavy-ion physics, much in the same way as studies of non-Gaussian fluctuations [15] in the early Universe. They bring in a large number of new observables which provide new, detailed insight into the hydrodynamic response and on the initial stage, and will significantly improve our understanding of heavy-ion collisions. The ATLAS collaboration [14] has recently released preliminary measurements of eight two-plane correlators (e.g., the correlation between the second and fourth harmonics) and six three-plane correlators (e.g., the mixed correlation between second, third and fifth harmonics) in Pb-Pb collisions at √ sNN = 2.76 TeV, as a function of the centrality of the collision. These correlators are qualitatively understood within event-by-event hydrodynamics [16] and provide new insight [17] into the interplay between the linear and nonlinear [18] hydrodynamic response [19, 20] to the initial density profile. The ATLAS analysis is very demanding in terms of detector acceptance: each event plane is determined in a separate pseudorapidity window; windows must be pairwise separated by gaps in order to suppress nonflow correlations; finally, each window must be wide enough to achieve a significant resolution in every Fourier harmonic up to order six. In this article, we show that the analysis can be done more simply, and that even three- and four-plane correlators can be safely analyzed with just two symmetric pseudorapidity windows, in the same way as two-plane correlators. The analysis can thus be performed by other experiments with smaller detector acceptance. We also explain in detail how to generalize the scalar-product method used earlier for two-particle flow analysis [21], to mixed correlations, so as to eliminate the ambiguity brought about by the event-plane method [22]. We carry out realistic simulations within a multiphase transport (AMPT) model [23]. Results are for the first time in quantitative agreement with the ATLAS measurements. In addition, we present predictions for several new correlators, in particular four-plane correlators. Method.−The azimuthal distribution of outgoing particles is decomposed in Fourier harmonics in each collision event. The flow vector in harmonic n is defined as [24],
120847496
Multiplicity scaling in nuclear fragmentation
123325200
Production of antinuclei and hypernuclei in a relativistic Hagedorn resonance gas model