14,357 research outputs found
Evolution of Primordial Black Hole Mass Spectrum in Brans-Dicke Theory
We investigate the evolution of primordial black hole mass spectrum by
including both accretion of radiation and Hawking evaporation within
Brans-Dicke cosmology in radiation, matter and vacuum-dominated eras. We also
consider the effect of evaporation of primordial black holes on the expansion
dynamics of the universe. The analytic solutions describing the energy density
of the black holes in equilibrium with radiation are presented. We demonstrate
that these solutions act as attractors for the system ensuring stability for
both linear and nonlinear situations. We show, however, that inclusion of
accretion of radiation delays the onset of this equilibrium in all radiation,
matter and vacuum-dominated eras.Comment: 18 pages, one figur
Influence of surface roughness on superhydrophobicity
Superhydrophobic surfaces, with liquid contact angle theta greater than 150
degree, have important practical applications ranging from self-cleaning window
glasses, paints, and fabrics to low-friction surfaces. Many biological
surfaces, such as the lotus leaf, have hierarchically structured surface
roughness which is optimized for superhydrophobicity through natural selection.
Here we present a molecular dynamics study of liquid droplets in contact with
self-affine fractal surfaces. Our results indicate that the contact angle for
nanodroplets depends strongly on the root-mean-square surface roughness
amplitude but is nearly independent of the fractal dimension D_f of the
surface.Comment: 5 Pages, 6 figures. Minimal changes with respect to the previous
versio
Renormalization Group Equation and QCD Coupling Constant in the Presence of SU(3) Chromo-Electric Field
We solve renormalization group equation in QCD in the presence of SU(3)
constant chromo-electric field E^a with arbitrary color index a=1,2,...8 and
find that the QCD coupling constant \alpha_s depends on two independent
casimir/gauge invariants C_1=[E^aE^a] and C_2=[d_{abc}E^aE^bE^c]^2 instead of
one gauge invariant C_1=[E^aE^a]. The \beta function is derived from the
one-loop effective action. This coupling constant may be useful to study hadron
formation from color flux tubes/strings at high energy colliders and to study
quark-gluon plasma formation at RHIC and LHC.Comment: 13 pages latex, 4 eps figs, Eur. Phys. J.
Spin polarization of the quantum Hall state
We report on results of numerical studies of the spin polarization of the
half filled second Landau level, which corresponds to the fractional quantum
Hall state at filling factor . Our studies are performed using both
exact diagonalization and Density Matrix Renormalization Group (DMRG) on the
sphere. We find that for the Coulomb interaction the exact finite-system ground
state is fully polarized, for shifts corresponding to both the Moore-Read
Pfaffian state and its particle-hole conjugate (anti-Pfaffian). This result is
found to be robust against small variations of the interaction. The low-energy
excitation spectrum is consistent with spin-wave excitations of a
fully-magnetized ferromagnet.Comment: Final version published on PR
O(4)-Invariant Formulation of the Nodal Liquid
We consider the O(4) symmetric point in the phase diagram of an electron
system in which there is a transition between d_{x^2 - y^2} density-wave order
and d_{x^2 - y^2} superconductivity. If the pseudospin
symmetry is disordered by quantum fluctuations, the Nodal Liquid can result. In
this context, we (1) construct a pseudospin -model; (2) discuss its
topological excitations; (3) point out the possibility of a {\it
pseudospin-Peierls} state and (4) propose a phase diagram for the underdoped
cuprate superconductors
Gauge-Invariant Quantities Characterizing Gauge Fields in Chromodynamics
We calculate Lorentz-invariant and gauge-invariant quantities characterizing
the product , where denotes the matrix
for the generator in the representation fundamental and adjoint, for
color SU(3). We also present analogous results for an SU(2) gauge theory
Geotechnical Studies of Foundation of a Tilted Tank at Parikshatgarh, India
An overhead tank of 200 KL capacity and 9 m staging was constructed in year 1975 at the ancient historical site at Parikshatgarh, Meerut, India. The depth of foundation is 1.6 m and inner and outer diameters of annular raft is 6.8 m and 10.3 respectively. In year 1978, the overhead tank was observed to be tilted. Detailed geotechnical studies have been conducted in 1987 to find out the causes of tilting of the tank and tilts have been measured every month for last one year. It is interesting to note that in spite of severe tilt of 4.3 cm/meter height the overhead tank has been functioning satisfactorily for last 12 years. A comparison of estimated, permissible and observed total and differential settlements has been made
Geotechnical Studies of Foundation of a Tilted Tank at Parikshatgarh, India
An overhead tank of 200 KL capacity and 9 m staging was constructed in year 1975 at the ancient historical site at Parikshatgarh, Meerut, India. The depth of foundation is 1.6 m and inner and outer diameters of annular raft is 6.8 m and 10.3 respectively. In year 1978, the overhead tank was observed to be tilted. Detailed geotechnical studies have been conducted in 1987 to find out the causes of tilting of the tank and tilts have been measured every month for last one year. It is interesting to note that in spite of severe tilt of 4.3 cm/meter height the overhead tank has been functioning satisfactorily for last 12 years. A comparison of estimated, permissible and observed total and differential settlements has been made
Production and Equilibration of the Quark-Gluon Plasma with Chromoelectric Field and Minijets
Production and equilibration of quark-gluon plasma are studied within the
color flux-tube model, at the RHIC and LHC energies. Non-Abelian relativistic
transport equations for quarks, antiquarks and gluons, are solved in the
extended phase space which includes coordinates, momenta and color. Before the
chromoelectric field is formed, hard and semihard partons are produced via
minijets which provide the initial conditions necessary to solve the transport
equations. The model predicts that in spite of the vast difference between the
RHIC and LHC incident energies, once the local equilibrium is reached, the
energy densities, the number densities and the temperatures at the two machines
may not be very different from each other. The minijet input significantly
alters the evolution of the deconfined matter, unless the color field is too
strong. For the input parameters used here the equilibration time is estimated
to be fm at RHIC and fm at LHC, measured from the instant
when the two colliding nuclei have just passed through each other. The
temperature at equilibration is found to be MeV at RHIC and MeV at LHC.Comment: version to appear in Phys. Rev. C; discussion enlarged to include
comparison with other models; conclusions unchanged; 14 single-spaced pages +
8 ps figure
Integrability and explicit solutions in some Bianchi cosmological dynamical systems
The Einstein field equations for several cosmological models reduce to
polynomial systems of ordinary differential equations. In this paper we shall
concentrate our attention to the spatially homogeneous diagonal G_2
cosmologies. By using Darboux's theory in order to study ordinary differential
equations in the complex projective plane CP^2 we solve the Bianchi V models
totally. Moreover, we carry out a study of Bianchi VI models and first
integrals are given in particular cases
- …