35 research outputs found
Predictions from Quantum Cosmology
The world view suggested by quantum cosmology is that inflating universes
with all possible values of the fundamental constants are spontaneously created
out of nothing. I explore the consequences of the assumption that we are a
`typical' civilization living in this metauniverse. The conclusions include
inflation with an extremely flat potential and low thermalization temperature,
structure formation by topological defects, and an appreciable cosmological
constant.Comment: (revised version), 15 page
Sign reversal of the order parameter in s-wave superconductors
We show that in a superconductor where two or more bands cross the Fermi
level it is possible, in the framework of the conventional (s-wave) BCS theory,
that the sign of the superconducting gap is different on the different sheets
of the Fermi surface. At least one of two conditions has to be satisfied: (1)
The interband pairing interaction is weaker than the Coulomb pseudopotential,
while the intraband one is stronger, or (2) there is strong interband
scattering by magnetic impurities. In the case of YBa% CuO we shall
argue that the first condition is possibly satisfied, and the second one very
likely satisfied. In many aspects such a sign-reversal wave superconductor
is similar to a d-wave superconductor, and thus demands revising recent
experiments aimed to distinguish between the and wave
superconductivity in this compound.Comment: RevTex; Physica C, in pres
Stationarity of Inflation and Predictions of Quantum Cosmology
We describe several different regimes which are possible in inflationary
cosmology. The simplest one is inflation without self-reproduction of the
universe. In this scenario the universe is not stationary. The second regime,
which exists in a broad class of inflationary models, is eternal inflation with
the self-reproduction of inflationary domains. In this regime local properties
of domains with a given density and given values of fields do not depend on the
time when these domains were produced. The probability distribution to find a
domain with given properties in a self-reproducing universe may or may not be
stationary, depending on the choice of an inflationary model. We give examples
of models where each of these possibilities can be realized, and discuss some
implications of our results for quantum cosmology. In particular, we propose a
new mechanism which may help solving the cosmological constant problem.Comment: 30 pages, Stanford preprint SU-ITP-94-24, LaTe
Axion-induced oscillations of cooperative electric field in a cosmic magneto-active plasma
We consider one cosmological application of an axionic extension of the
Maxwell-Vlasov theory, which describes axionically induced oscillatory regime
in the state of global magnetic field evolving in the anisotropic expanding
(early) universe. We show that the cooperative electric field in the
relativistic plasma, being coupled to the pseudoscalar (axion) and global
magnetic fields, plays the role of a regulator in this three-level system; in
particular, the cooperative (Vlasov) electric field converts the regime of
anomalous growth of the pseudoscalar field, caused by the axion-photon coupling
at the inflationary epoch of the universe expansion, into an oscillatory regime
with finite density of relic axions. We analyze solutions to the dispersion
equations for the axionically induced cooperative oscillations of the electric
field in the relativistic plasma.Comment: 7 pages, misprints correcte
Theory of Melting and the Optical Properties of Gold/DNA Nanocomposites
We describe a simple model for the melting and optical properties of a
DNA/gold nanoparticle aggregate. The optical properties at fixed wavelength
change dramatically at the melting transition, which is found to be higher and
narrower in temperature for larger particles, and much sharper than that of an
isolated DNA link. All these features are in agreement with available
experiments. The aggregate is modeled as a cluster of gold nanoparticles on a
periodic lattice connected by DNA bonds, and the extinction coefficient is
computed using the discrete dipole approximation. Melting takes place as an
increasing number of these bonds break with increasing temperature. The melting
temperature corresponds approximately to the bond percolation threshold.Comment: 5 pages, 4 figure. To be published in Phys. Rev.
Structure Formation, Melting, and the Optical Properties of Gold/DNA Nanocomposites: Effects of Relaxation Time
We present a model for structure formation, melting, and optical properties
of gold/DNA nanocomposites. These composites consist of a collection of gold
nanoparticles (of radius 50 nm or less) which are bound together by links made
up of DNA strands. In our structural model, the nanocomposite forms from a
series of Monte Carlo steps, each involving reaction-limited cluster-cluster
aggregation (RLCA) followed by dehybridization of the DNA links. These links
form with a probability which depends on temperature and particle
radius . The final structure depends on the number of monomers (i. e. gold
nanoparticles) , , and the relaxation time. At low temperature, the
model results in an RLCA cluster. But after a long enough relaxation time, the
nanocomposite reduces to a compact, non-fractal cluster. We calculate the
optical properties of the resulting aggregates using the Discrete Dipole
Approximation. Despite the restructuring, the melting transition (as seen in
the extinction coefficient at wavelength 520 nm) remains sharp, and the melting
temperature increases with increasing as found in our previous
percolation model. However, restructuring increases the corresponding link
fraction at melting to a value well above the percolation threshold. Our
calculated extinction cross section agrees qualitatively with experiments on
gold/DNA composites. It also shows a characteristic ``rebound effect,''
resulting from incomplete relaxation, which has also been seen in some
experiments. We discuss briefly how our results relate to a possible sol-gel
transition in these aggregates.Comment: 12 pages, 10 figure
Smooth hybrid inflation in supergravity with a running spectral index and early star formation
It is shown that in a smooth hybrid inflation model in supergravity adiabatic
fluctuations with a running spectral index with \ns >1 on a large scale and
\ns <1 on a smaller scale can be naturally generated, as favored by the
first-year data of WMAP. It is due to the balance between the nonrenormalizable
term in the superpotential and the supergravity effect. However, since smooth
hybrid inflation does not last long enough to reproduce the central value of
observation, we invoke new inflation after the first inflation. Its initial
condition is set dynamically during smooth hybrid inflation and the spectrum of
fluctuations generated in this regime can have an appropriate shape to realize
early star formation as found by WMAP. Hence two new features of WMAP
observations are theoretically explained in a unified manner.Comment: 12 pages, 1 figure, to appear in Phys. Rev.
Solitary wave solution to the generalized nonlinear Schrodinger equation for dispersive permittivity and permeability
We present a solitary wave solution of the generalized nonlinear Schrodinger
equation for dispersive permittivity and permeability using a scaling
transformation and coupled amplitude-phase formulation. We have considered the
third-order dispersion effect (TOD) into our model and show that soliton shift
may be suppressed in a negative index material by a judicious choice of the TOD
and self-steepening parameter.Comment: 6 page
Electromagnetic waves in an axion-active relativistic plasma non-minimally coupled to gravity
We consider cosmological applications of a new self-consistent system of
equations, accounting for a nonminimal coupling of the gravitational,
electromagnetic and pseudoscalar (axion) fields in a relativistic plasma. We
focus on dispersion relations for electromagnetic perturbations in an initially
isotropic ultrarelativistic plasma coupled to the gravitational and axion
fields in the framework of isotropic homogeneous cosmological model of the de
Sitter type. We classify the longitudinal and transversal electromagnetic modes
in an axionically active plasma and distinguish between waves (damping,
instable or running), and nonharmonic perturbations (damping or instable). We
show that for the special choice of the guiding model parameters the
transversal electromagnetic waves in the axionically active plasma,
nonminimally coupled to gravity, can propagate with the phase velocity less
than speed of light in vacuum, thus displaying a possibility for a new type of
resonant particle-wave interactions.Comment: 19 pages, 9 figures, published versio
Background Dependent Lorentz Violation: Natural Solutions to the Theoretical Challenges of the OPERA Experiment
To explain both the OPERA experiment and all the known phenomenological
constraints/observations on Lorentz violation, the Background Dependent Lorentz
Violation (BDLV) has been proposed. We study the BDLV in a model independent
way, and conjecture that there may exist a "Dream Special Relativity Theory",
where all the Standard Model (SM) particles can be subluminal due to the
background effects. Assuming that the Lorentz violation on the Earth is much
larger than those on the interstellar scale, we automatically escape all the
astrophysical constraints on Lorentz violation. For the BDLV from the effective
field theory, we present a simple model and discuss the possible solutions to
the theoretical challenges of the OPERA experiment such as the Bremsstrahlung
effects for muon neutrinos and the pion decays. Also, we address the Lorentz
violation constraints from the LEP and KamLAMD experiments. For the BDLV from
the Type IIB string theory with D3-branes and D7-branes, we point out that the
D3-branes are flavour blind, and all the SM particles are the conventional
particles as in the traditional SM when they do not interact with the
D3-branes. Thus, we not only can naturally avoid all the known phenomenological
constraints on Lorentz violation, but also can naturally explain all the
theoretical challenges. Interestingly, the energy dependent photon velocities
may be tested at the experiments.Comment: RevTex4, 14 pages, minor corrections, references adde