1,886 research outputs found
Cosmological perturbations in massive gravity with doubly coupled matter
We investigate the cosmological perturbations around FLRW solutions to non- linear massive gravity with a new effective coupling to matter proposed recently. Unlike the case with minimal matter coupling, all five degrees of freedom in the gravity sector propagate on generic self-accelerating FLRW backgrounds. We study the stability of the cosmological solutions and put constraints on the parameters of the theory by demanding the correct sign for the kinetic terms for scalar, vector and tensor perturbations
Dynamical gravities
It is offered that modified gravities can be considered as
nonperturbative quantum effects arising from Einstein gravity. It is assumed
that nonperturbative quantum effects gives rise to the fact that the connection
becomes incompatible with the metric, the metric factors and the square of the
connection in Einstein - Hilbert Lagrangian have nonperturbative additions. In
the simplest approximation both additions can be considered as functions of one
scalar field. The scalar field can be excluded from the Lagrangian obtaining
gravity. The essence of quantum correction to the affine connection as a
torsion is discussed.Comment: discussion on quantum corrections is adde
On geometric relativistic foundations of matter field equations and plane wave solutions
In this paper, we start from the geometric relativistic foundations to define
the basis upon which matter field theories are built, and their wave solutions
are investigated, finding that they display repulsive interactions able to
reproduce the exclusion principle in terms of its effects in a dynamical way,
then discussing possible consequences and problems.Comment: 11 page
Semiclassical Calculation of Multiparticle Scattering Cross Sections in Classicalizing Theories
It has been suggested in arXiv:1010.1415 that certain derivatively coupled
non-renormalizable scalar field theories might restore the perturbative
unitarity of high energy hard scatterings by classicalization, i.e. formation
of multiparticle states of soft quanta. Here we apply the semiclassical method
of calculating the multiparticle production rates to the scalar
Dirac-Born-Infeld (DBI) theory which is suggested to classicalize. We find that
the semiclassical method is applicable for the energies in the final state
above the cutoff scale of the theory L_*^{-1}. We encounter that the cross
section of the process two to N ceases to be exponentially suppressed for the
particle number in the final state N smaller than a critical particle number
N_{crit} ~ (E L_*)^{4/3}. It coincides with the typical particle number
produced in two-particle collisions at high energies predicted by
classicalization arguments.Comment: 17 pages, 4 figures, v2. Minor changes to match the published versio
Measuring measurement--disturbance relationships with weak values
Using formal definitions for measurement precision {\epsilon} and disturbance
(measurement backaction) {\eta}, Ozawa [Phys. Rev. A 67, 042105 (2003)] has
shown that Heisenberg's claimed relation between these quantities is false in
general. Here we show that the quantities introduced by Ozawa can be determined
experimentally, using no prior knowledge of the measurement under investigation
--- both quantities correspond to the root-mean-squared difference given by a
weak-valued probability distribution. We propose a simple three-qubit
experiment which would illustrate the failure of Heisenberg's
measurement--disturbance relation, and the validity of an alternative relation
proposed by Ozawa
The Evolution of Universe with th B-I Type Phantom Scalar Field
We considered the phantom cosmology with a lagrangian ,
which is original from the nonlinear Born-Infeld type scalar field with the
lagrangian . This cosmological model can explain the
accelerated expansion of the universe with the equation of state parameter
. We get a sufficient condition for a arbitrary potential to admit a
late time attractor solution: the value of potential at the critical
point should be maximum and large than zero. We study a specific
potential with the form of
via phase plane
analysis and compute the cosmological evolution by numerical analysis in
detail. The result shows that the phantom field survive till today (to account
for the observed late time accelerated expansion) without interfering with the
nucleosynthesis of the standard model(the density parameter
at the equipartition epoch), and also avoid the
future collapse of the universe.Comment: 17 pages, 10 figures,typos corrected, references added,figures added
and enriched, title changed, main result remaine
Kinetic energy driven superconductivity, the origin of the Meissner effect, and the reductionist frontier
Is superconductivity associated with a lowering or an increase of the kinetic
energy of the charge carriers? Conventional BCS theory predicts that the
kinetic energy of carriers increases in the transition from the normal to the
superconducting state. However, substantial experimental evidence obtained in
recent years indicates that in at least some superconductors the opposite
occurs. Motivated in part by these experiments many novel mechanisms of
superconductivity have recently been proposed where the transition to
superconductivity is associated with a lowering of the kinetic energy of the
carriers. However none of these proposed unconventional mechanisms explores the
fundamental reason for kinetic energy lowering nor its wider implications. Here
I propose that kinetic energy lowering is at the root of the Meissner effect,
the most fundamental property of superconductors. The physics can be understood
at the level of a single electron atom: kinetic energy lowering and enhanced
diamagnetic susceptibility are intimately connected. According to the theory of
hole superconductivity, superconductors expel negative charge from their
interior driven by kinetic energy lowering and in the process expel any
magnetic field lines present in their interior. Associated with this we predict
the existence of a macroscopic electric field in the interior of
superconductors and the existence of macroscopic quantum zero-point motion in
the form of a spin current in the ground state of superconductors (spin
Meissner effect). In turn, the understanding of the role of kinetic energy
lowering in superconductivity suggests a new way to understand the fundamental
origin of kinetic energy lowering in quantum mechanics quite generally
Symmetry-preserving Loop Regularization and Renormalization of QFTs
A new symmetry-preserving loop regularization method proposed in \cite{ylw}
is further investigated. It is found that its prescription can be understood by
introducing a regulating distribution function to the proper-time formalism of
irreducible loop integrals. The method simulates in many interesting features
to the momentum cutoff, Pauli-Villars and dimensional regularization. The loop
regularization method is also simple and general for the practical calculations
to higher loop graphs and can be applied to both underlying and effective
quantum field theories including gauge, chiral, supersymmetric and
gravitational ones as the new method does not modify either the lagrangian
formalism or the space-time dimension of original theory. The appearance of
characteristic energy scale and sliding energy scale offers a
systematic way for studying the renormalization-group evolution of gauge
theories in the spirit of Wilson-Kadanoff and for exploring important effects
of higher dimensional interaction terms in the infrared regime.Comment: 13 pages, Revtex, extended modified version, more references adde
Classification of life by the mechanism of genome size evolution
The classification of life should be based upon the fundamental mechanism in
the evolution of life. We found that the global relationships among species
should be circular phylogeny, which is quite different from the common sense
based upon phylogenetic trees. The genealogical circles can be observed clearly
according to the analysis of protein length distributions of contemporary
species. Thus, we suggest that domains can be defined by distinguished
phylogenetic circles, which are global and stable characteristics of living
systems. The mechanism in genome size evolution has been clarified; hence main
component questions on C-value enigma can be explained. According to the
correlations and quasi-periodicity of protein length distributions, we can also
classify life into three domains.Comment: 53 pages, 9 figures, 2 table
On the instability of classical dynamics in theories with higher derivatives
The development of instability in the dynamics of theories with higher
derivatives is traced in detail in the framework of the Pais-Uhlenbeck fourth
oder oscillator. For this aim the external friction force is introduced in the
model and the relevant solutions to equations of motion are investigated. As a
result, the physical implication of the energy unboundness from below in
theories under consideration is revealed.Comment: 9 pages, no figures and no tables, revtex4; a few misprints are
correcte
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