14 research outputs found

### Dynamical Restoration of Z_N Symmetry in SU(N)+Higgs Theories

We study the Z_N symmetry in SU(N)+Higgs theories with the Higgs field in the
fundamental representation. The distributions of the Polyakov loop show that
the Z_N symmetry is explicitly broken in the Higgs phase. On the other hand,
inside the Higgs symmetric phase the Polyakov loop distributions and other
physical observables exhibit the Z_N symmetry. This effective restoration of
the Z_N symmetry changes the nature of the confinement-deconfinenement
transition. We argue that the Z_N symmetry will lead to time independent
topological defect solutions in the Higgs symmetric deconfined phase which will
play important role at high temperatures.Comment: 13 pages, 4 figure

### Analyzing flow anisotropies with excursion sets in relativistic heavy-ion collisions

We show that flow anisotropies in relativistic heavy-ion collisions can be
analyzed using a certain technique of shape analysis of excursion sets recently
proposed by us for CMBR fluctuations to investigate anisotropic expansion
history of the universe. The technique analyzes shapes (sizes) of patches above
(below) certain threshold value for transverse energy/particle number (the
excursion sets) as a function of the azimuthal angle and rapidity. Modeling
flow by imparting extra anisotropic momentum to the momentum distribution of
particles from HIJING, we compare the resulting distributions for excursion
sets at two different azimuthal angles. Angles with maximum difference in the
two distributions identify the event plane, and the magnitude of difference in
the two distributions relates to the magnitude of momentum anisotropy, i.e.
elliptic flow.Comment: 5 pages, 4 figure

### Hawking radiation from acoustic black holes in hydrodynamic flow of electrons

Acoustic black holes are formed when a fluid flowing with subsonic
velocities, accelerates and becomes supersonic. When the flow is directed from
the subsonic to supersonic region, the surface on which the normal component of
fluid velocity equals the local speed of sound acts as an acoustic horizon.
This is because no acoustic perturbation from the supersonic region can cross
it to reach the subsonic part of the fluid. One can show that if the fluid
velocity is locally irrotational, the field equations for acoustic
perturbations of the velocity potential are identical to that of a massless
scalar field propagating in a black hole background. One, therefore, expects
Hawking radiation in the form of a thermal spectrum of phonons. There have been
numerous investigations of this possibility, theoretically, as well as
experimentally, in systems ranging from cold atom systems to quark-gluon plasma
formed in relativistic heavy-ion collisions. Here we investigate this
possibility in the hydrodynamic flow of electrons. Resulting Hawking radiation
in this case should be observable in terms of current fluctuations. Further,
current fluctuations on both sides of the acoustic horizon should show
correlations expected for pairs of Hawking particles.Comment: 7 pages, 2 figure

### On viscous flow and azimuthal anisotropy of quark-gluon plasma in strong magnetic field

We calculate the viscous pressure tensor of the quark-gluon plasma in strong
magnetic field. It is azimuthally anisotropic and is characterized by five
shear viscosity coefficients, four of which vanish when the field strength eB
is much larger than the plasma temperature squared. We argue, that the
azimuthally anisotropic viscous pressure tensor generates the transverse flow
with asymmetry as large as 1/3, even not taking into account the collision
geometry. We conclude, that the magnitude of the shear viscosity extracted from
the experimental data ignoring the magnetic field must be underestimated.Comment: 10 page

### Probing the anisotropic expansion history of the universe with cosmic microwave background

We propose a simple technique to detect any anisotropic expansion stage in
the history of the universe starting from the inflationary stage to the surface
of last scattering from the CMBR data. We use the property that any anisotropic
expansion in the universe would deform the shapes of the primordial density
perturbations and this deformation can be detected in a shape analysis of
superhorizon fluctuations in CMBR. Using this analysis we obtain the constraint
on any previous anisotropic expansion of the universe to be less than about
35%.Comment: 16 pages, 11 figures (color online