Sharif Digital Repository

To study the rate of energy and momentum loss of a heavy quark in QGP, specifically in the hydrodynamic regime, we use fluid/gravity duality and construct a perturbative procedure to find the string solution in gravity side. We show that by this construction, the position of the world-sheet horizon and thereby the drag force exerted on the quark can be computed perturbatively, order by order in a boundary derivative expansion, for a wide range of quark velocities. At ideal order, our result is just the localized expression of the drag force exerted on a moving quark in thermal plasma, while for a quark whose velocity does not belong to the mentioned range, we predict a nonlocal drag force.... 

In the framework of chiral kinetic theory (CKT), we consider a system of right-and left-handed Weyl fermions out of thermal equilibrium in a homogeneous weak magnetic field. We show that the Lorentz invariance implies a modification in the definition of the momentum current in the phase space, compared to the case in which the system is in global equilibrium. Using this modified momentum current, we derive the linearized conservation equations from the kinetic equation up to second order in the derivative expansion. It turns out that the eigenmodes of these equations, namely the hydrodynamic modes, differ from those obtained from the hydrodynamic in the Landau-Lifshitz (LL) frame at the same... 

We consider a fluid with weakly broken time and translation symmetries. We assume the fluid also possesses a U(1) symmetry which is not only weakly broken, but is anomalous. We use the second order chiral quasi-hydrodynamics to compute the magneto conductivities of this fluid in the presence of a weak magnetic field. Analogous to the electrical and thermoelectric conductivities, it turns out that the thermal conductivity depends on the coefficient of mixed gauge-gravitational anomaly. Our results can be applied to the hydrodynamic regime of every arbitrary system, once the thermodynamics of that system is known. By applying them to a free system of Weyl fermions at low temperature limit T ≪... 

We determine the most general form of the covariant drag force exerted on a quark moving through a fluid dynamical flow. Up to first order in derivative expansion, our general formula requires the specification of seven coefficient functions. We use the perturbative method introduced in arXiv:1202.2737 and find all these coefficients in the hydrodynamic regime of a N = 4 SYM plasma. Having this general formula, we can obtain the rate of the energy and momentum loss of a quark, namely the drag force, in a general flow. This result makes it possible to perturbatively study the motion of heavy quarks moving through the Bjorken flow up to first order in derivative expansion  

Here we introduce a phase-shifting digital holography-based method to determine the temperature profile around an irradiated (sub-)micron spherical bead. The method utilizes a Mach-Zehnder interferometer implemented into an open setup microscope. The results of irradiated gold spheres with diameter of 400 nm and also silver-coated micron-sized silica beads embedded in silicone oil are presented. We show that the applied method is able to accurately determine the surface temperature with accuracy of 1 °C. Our experimental results perfectly confirm the theoretical prediction of temperature profile around the irradiated bead  

In this article, we present a novel framework based on incoherent holography (IH) and optical phase conjugation (OPC) principle for imaging through scattering media. While many different methods have recently addressed the issue of focusing light inside scattering media or through-scatterer imaging, the majority of them suffer from severe drawbacks, such as demanding for a high-intensity and narrow-bandwidth laser illumination and an extremely stable optical setup in digital holography as the normal disadvantages of interferometry. On the contrary, our proposed framework relaxes the need for interferometry by getting advantage of its IH-based structure. Our newly presented approach for... 

We use holographic methods to study the entanglement entropy for excited states in a two dimensional conformal field theory. The entangling area is a single interval and the excitations are produced by in and out vertex operators with given scaling dimensions. On the gravity side we provide the excitations by turning on a scalar field with an appropriate mass. The calculation amounts to using the gravitational background, with a singular boundary, to find the one point function of the vertex operators. The singular boundary is taken care of by introducing a nontrivial UV regulator surface to calculate gravitational partition functions. By means of holographic methods we reproduce the field... 

We argue that in order to study the magneto-transport in a relativistic Weyl fluid, it is needed to take into account the associated quantum corrections, namely the side-jump effect, at least to second order. To this end, we impose Lorentz invariance to a system of free Weyl fermions in the presence of the magnetic field and find the second order correction to the energy dispersion. By developing a scheme to compute the integrals in the phase space, we show that the mentioned correction has non-trivial effects on the thermodynamics of the system. Specifically, we compute the expression of the negative magnetoresistivity in the system from the enthalpy density in equilibrium. Then in analogy... 

In this paper, general form of optimum distribution free (D.F.) detector for noncoherent radars is extracted. This general form is very complex to be analyzed, therefore, we have derived two special cases and one case which is more interesting and practical is analyzed accurately. We have shown that in spite of its simple form, the detector has considerable benefits over conventional OSCFAR schemes  

In this paper it is shown that the entropy of the black hole horizon in Achúcarro-Ortiz spacetime, which is the most general two-dimensional black hole derived from the three-dimensional rotating Banados-Teitelboim- Zanelli black hole, can be described by the Cardy-Verlinde formula. The latter is supposed to be an entropy formula of conformai field theory in any dimension. © 2003 The American Physical Society