2,879 research outputs found
Equivalence of the Beta-function of the Variational Approach to that of QCD
The variational ansatz for the ground state wavefunctional of QCD is found to
capture the anti-screening behaviour that contributes the dominant `-4' to the
beta-function and leads to asymptotic freedom. By considering an SU(N) purely
gauge theory in the Hamiltonian formalism and choosing the Coulomb gauge, the
origins of all screening and anti-screening contributions in gluon processes
are found in terms of the physical degrees of freedom. The overwhelming anti-
screening contribution of `-4' is seen to originate in the renormalisation of a
Coulomb interaction by a transverse gluon. The lesser screening contribution of
`1/3' is seen to originate in processes involving transverse gluon
interactions. It is thus apparent how the variational ansatz must be developed
to capture the full running of the QCD coupling constant.Comment: 35 pages, 11 figures, LaTe
Pseudo Jahn-Teller Effect In The Origin Of Enhanced Flexoelectricity
The controversy between the theory and experiment in explaining the origin of enhanced flexoelectricity is removed by taking into account the pseudo Jahn-Teller effect (PJTE) which, under certain conditions, creates local dipolar distortions of dynamic nature, resonating between two or more equivalent orientations. The latter become nonequivalent under a strain gradient thus producing enhanced flexoelectricity: it is much easier to orient ready-made dipoles than to polarize an ionic solid. For BaTiO3, the obtained earlier numerical data for the adiabatic potential energy surface in the space of dipolar displacements in the Ti centers were used to estimate the flexoelectric coefficient integral in the paraelectric phase in a one-dimensional model with the strain gradient along the [111] direction: integral = -0.43 X 10(-6) Cm-1. This eliminates the huge contradiction between the experimental data of integral similar to mu Cm-1 for this case and the theoretical predictions (without the PJTE) of 3-4 orders-of-magnitude smaller values. Enhanced flexoelectricity is thus expected in solids with a sufficient density of centers that have PJTE induced dipolar instabilities. It explains also the origin of enhanced flexoelectricity observed in other solids, noticeable containing Nb perovskite centers which are known to have a PJTE instability, similar to that of Ti centers. The SrTiO3 crystal as a virtual ferroelectric in which the strain gradient eases the condition of PJTE polar instability is also discussed. (C) 2015 AIP Publishing LLC.Institute for Theoretical Chemistr
Growth and formation of the foreleg skeleton inbred mice and rats under conditions of hypo-, normo- and hyperdynamia
Inbred 1 month old males of C57B 1/6, CBA, CC57Br/Mw interlinear hybrid mice of the first generation and rats of the August and Wistar lines were subjected to conditions of hypo-, normo- and hyperdynamia for 2 months. The statistically reliable dependence is shown between mechanical underloadings and overloadings and macro microscopic changes in the hind limb skeleton of animals. Genetic determination of growth and formation of the forelimb skeleton is established. Hereditary susceptibility and the phenomenon of heterosis are preserved under all motor conditions
Statistics of fluctuations for two types of crossover: from ballistic to diffusive regime and from orthogonal to unitary ensemble
In our previous publication [Kogan et al, Phys. Rev. {\bf 48}, 9404 (1993)]
we considered the issue of statistics of radiation diffusively propagating in a
disordered medium. The consideration was in the framework of diagrammatic
techniques and a new representation for the intensity distribution function in
terms of connected diagrams only was proposed. Here we use similar approach to
treat the issue of statistics in the regime of the crossover between ballistic
and diffusive transport. We find that even small contribution from coherent
component decreases by one half the intensity distribution function for small
values of intensity and also produces oscillations of the distribution
function. We also apply this method to study statistics of fluctuations of wave
functions of chaotic electrons in a quantum dot in an arbitrary magnetic field,
by calculating the single state local density in the regime of the crossover
between the orthogonal and unitary ensemble.Comment: Revtex, 3 pages + 2 ps.figures in uuencoded file, a version which
clarifies and unites the results of two previous submission
Conductance noise in interacting Anderson insulators driven far from equilibrium
The combination of strong disorder and many-body interactions in Anderson
insulators lead to a variety of intriguing non-equilibrium transport phenomena.
These include slow relaxation and a variety of memory effects characteristic of
glasses. Here we show that when such systems are driven with sufficiently high
current, and in liquid helium bath, a peculiar type of conductance noise can be
observed. This noise appears in the conductance versus time traces as
downward-going spikes. The characteristic features of the spikes (such as
typical width) and the threshold current at which they appear are controlled by
the sample parameters. We show that this phenomenon is peculiar to hopping
transport and does not exist in the diffusive regime. Observation of
conductance spikes hinges also on the sample being in direct contact with the
normal phase of liquid helium; when this is not the case, the noise exhibits
the usual 1/f characteristics independent of the current drive. A model based
on the percolative nature of hopping conductance explains why the onset of the
effect is controlled by current density. It also predicts the dependence on
disorder as confirmed by our experiments. To account for the role of the bath,
the hopping transport model is augmented by a heuristic assumption involving
nucleation of cavities in the liquid helium in which the sample is immersed.
The suggested scenario is analogous to the way high-energy particles are
detected in a Glaser's bubble chamber.Comment: 15 pages 22 figure
Generalized parity transformations in the regularized Chern-Simons theory
We study renormalization effects in the Abelian Chern-Simons (CS) action.
These effects can be non-trivial when the gauge field is coupled to dynamical
matter, since the regularization of the UV divergences in the model forces the
introduction of a parity even piece in the gauge field action. This changes the
classical (odd) transformation properties of the pure CS action. This effect,
already discussed for the case of a lattice regularization by F. Berruto, M.C.
Diamantini and P. Sodano in hep-th/0004203, is also present when the theory is
defined in the continuum and, indeed, it is a manifestation of a more general
`anomalous' effect, since it happens for every regularization scheme. We
explore the physical consequences of this anomaly. We also show that
generalized, nonlocal parity transformations can be defined in such a way that
the regularized theory is odd, and that those transformations tend to the usual
ones when the cutoff is removed. These generalized transformations play a role
that is tantamount to the deformed symmetry corresponding to Ginsparg-Wilson
fermions [2] (in an even number of spacetime dimensions).Comment: 16 pages, LaTeX, references added and typos correcte
Effect of graded physical load on the state of the liver from morphometric data and biochemical blood indices of rats against a background of hypokinesia
Tests were conducted on 100 sexually immature inbred August and Wistar male rats in order to determine the effects hypokinesia, physical load and phenamine on the liver. Weight and linear dimension fell in hypokinesia; total serum protein lowered and aldolase and cholesterol and beta-lipoprotein levels rose. Blood sugar content rose and liver glycogen fell. Interlinear differences of these indices are found. Rehabilitated physical loading against hypokinesia background diminished and at times completely prevented its negative effect. Extent of correction depended on animal species. Evidence of genotypical conditionality of organism adaptation to physical load in hypokinesia was found
Effective Lagrangian from Higher Curvature Terms: Absence of vDVZ Discontinuity in AdS Space
We argue that the van Dam-Veltman-Zakharov discontinuity arising in the limit of the massive graviton through an explicit Pauli-Fierz mass term
could be absent in anti de Sitter space. This is possible if the graviton can
acquire mass spontaneously from the higher curvature terms or/and the massless
limit is attained faster than the cosmological constant . We discuss the effects of higher-curvature couplings and of an explicit
cosmological term () on stability of such continuity and of massive
excitations.Comment: 23 pages, Latex, the version to appear in Class. Quant. Gra
Spherically symmetric spacetimes in massive gravity
We explore spherically symmetric stationary solutions, generated by ``stars''
with regular interiors, in purely massive gravity. We reexamine the claim that
the resummation of non-linear effects can cure, in a domain near the source,
the discontinuity exhibited by the linearized theory as the mass m of the
graviton tends to zero. First, we find analytical difficulties with this claim,
which appears not to be robust under slight changes in the form of the mass
term. Second, by numerically exploring the inward continuation of the class of
asymptotically flat solutions, we find that, when m is ``small'', they all end
up in a singularity at a finite radius, well outside the source, instead of
joining some conjectured ``continuous'' solution near the source. We reopen,
however, the possibility of reconciling massive gravity with phenomenology by
exhibiting a special class of solutions, with ``spontaneous symmetry breaking''
features, which are close, near the source, to general relativistic solutions
and asymptote, for large radii, a de Sitter solution of curvature ~m^2.Comment: 57 pages, references addde
Difficulties in Inducing a Gauge Theory at Large N
It is argued that the recently proposed Kazakov-Migdal model of induced gauge
theory, at large , involves only the zero area Wilson loops that are
effectively trees in the gauge action induced by the scalars. This retains only
a constant part of the gauge action excluding plaquettes or anything like them
and the gauge variables drop out.Comment: 6 pages, Latex, AZPH-TH/93-01, COLO-HEP/30
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