2,187,496 research outputs found
Quantum effects from a purely geometrical relativity theory
A purely geometrical relativity theory results from a construction that
produces from three-dimensional space a happy unification of Kaluza's
five-dimensional theory and Weyl's conformal theory. The theory can provide
geometrical explanations for the following observed phenomena, among others:
(a) lifetimes of elementary particles of lengths inversely proportional to
their rest masses; (b) the equality of charge magnitude among all charged
particles interacting at an event; (c) the propensity of electrons in atoms to
be seen in discretely spaced orbits; and (d) `quantum jumps' between those
orbits. This suggests the possibility that the theory can provide a
deterministic underpinning of quantum mechanics like that provided to
thermodynamics by the molecular theory of gases.Comment: 7 pages, LaTeX jpconf.cls (Institute of Physics Publishing), 6
Encapsulated PostScript figures (Fig. 6 is 1.8M uncompressed); Presented at
VI Mexican School on Gravitation and Mathematical Physics "Approaches to
Quantum Gravity
Aggregation of self-propelled colloidal rods near confining walls
Non-equilibrium collective behavior of self-propelled colloidal rods in a
confining channel is studied using Brownian dynamics simulations and dynamical
density functional theory. We observe an aggregation process in which rods
self-organize into transiently jammed clusters at the channel walls. In the
early stage of the process, fast-growing hedgehog-like clusters are formed
which are largely immobile. At later stages, most of these clusters dissolve
and mobilize into nematized aggregates sliding past the walls.Comment: 5 pages, 4 figure
Casimir force for cosmological domain walls
We calculate the vacuum fluctuations that may affect the evolution of
cosmological domain walls. Considering domain walls, which are classically
stable and have interaction with a scalar field, we show that explicit symmetry
violation in the interaction may cause quantum bias that can solve the
cosmological domain wall problem.Comment: 15 pages, 2figure
A compact spectroradiometer for solar simulator measurements
Compact spectral irradiance probe has been designed and built which uses wedge filter in conjunction with silicon cell and operational amplifier. Probe is used to monitor spectral energy distribution of solar simulators and other high intensity sources
Generalized van der Waals theory for the twist elastic modulus and helical pitch of cholesterics
We present a generalized van der Waals theory for a lyotropic cholesteric
system of chiral spherocylinders based on the classical Onsager theory for hard
anisometric bodies. The rods consist of a hard spherocylindrical backbone
surrounded with a square-well potential to account for attractive (or soft
repulsive) interactions. Long-ranged chiral interactions are described by means
of a simple pseudo-scalar potential which is appropriate for weak chiral forces
of a predominant electrostatic origin. Based on the formalism proposed by
Straley [Phys. Rev. A {\bf 14}, 1835 (1976)] we derive explicit algebraic
expressions for the twist elastic modulus and the cholesteric pitch for rods as
a function of density and temperature. The pitch varies non-monotonically with
density, with a sharp decrease at low packing fractions and a marked increase
at higher packing fractions. A similar trend is found for the temperature
dependence. The unwinding of the helical pitch at high densities (or low
temperatures) originates from a marked increase in the local nematic order and
a steep increase of the twist elastic resistance associated with near-parallel
local rod configurations. This contrasts with the commonly held view that the
increase in pitch with decreasing temperature as often observed in cholesterics
is due to layer formation resulting from pre-smectic fluctuations. The increase
in pitch with increasing temperature is consistent with an entropic unwinding
as the chiral interaction becomes less and less significant than the thermal
energy. The variation of the pitch with density, temperature and contour length
is in qualitative agreement with recent experimental results on colloidal {\em
fd} rods.Comment: 17 pages, 6 figures, to appear in J. Chem. Phy
Dual Quantum Monte Carlo Algorithm for Hardcore Bosons
We derive the exact dual representation of the bosonic Hubbard model which
takes the form of conserved current loops. The hardcore limit, which
corresponds to the quantum spin- Heisenberg antiferromagnet, is
also obtained. In this limit, the dual partition function takes a particularly
simple form which is very amenable to numerical simulations. In addition to the
usual quantities that we can measure (energy, density-density correlation
function and superfluid density) we can with this new algorithm measure
efficiently the order parameter correlation function, . We demonstrate this with numerical tests in one dimension.Comment: 15 pages, 4 figures . Talk given at CCP1998, Granada, Spai
LOCV calculations for polarized liquid with the spin-dependent correlation
We have used the lowest order constrained variational (LOCV) method to
calculate some ground state properties of polarized liquid at zero
temperature with the spin-dependent correlation function employing the
Lennard-Jones and Aziz pair potentials. We have seen that the total energy of
polarized liquid increases by increasing polarization. For all
polarizations, it is shown that the total energy in the spin-dependent case is
lower than the spin-independent case. We have seen that the difference between
the energies of spin-dependent and spin-independent cases decreases by
increasing polarization. We have shown that the main contribution of the
potential energy comes from the spin-triplet state.Comment: 14 pages, 5 figures. Int. J. Mod. Phys. B (2008) in pres
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