180 research outputs found
T-violation in decay in a general two-Higgs doublet model
We calculate the transverse muon polarization in the process
arising from the Yukawa couplings of charged Higgs boson in a general two-Higgs
doublet model where spontaneous violation of CP is presentComment: 6 pages, latex, accepted for publication in Phys. Rev.
Association of the EPAS1 gene G/A polymorphism with successful performance in a group of Russian wrestlers
A large number of studies showed that the gene EPAS1 may serve as a possible predictor of success in sports because of its influence on the processes of oxygen transportation and consumption. However, data concerning the impact of EPAS1 polymorphisms on sports achievements in the modern research literature are very scarce and contradictory. The aim of the present paper was to study genetic selection in the polymorphic system of the EPAS1 gene (rs1867785) in a group of male sambo practitioners. 312 Russian males from 18 to 30 years of age were studied. Of them, 220 were professional athletes and 92 were non-athletes, who served as the control group. The genotype of a single nucleotide G/A polymorphic system of the EPAS1 gene was determined for each participant of the study. Analysis of genotype frequencies revealed statistically significant differences between the two groups. An increase of АА and AG genotype frequencies was revealed in the group of athletes (χ2 = 8.68, p = 0.01). Thus, for sambo practitioners, who reached high levels, the presence of the minor А-allele in the genotypes was typical. The odd ratio (OR) calculated for this group was 1.800 (95 % CI 1.227–2.641), demonstrating that the carriers of the А-allele of the EPAS1 gene had some advantages over the carriers of the G-allele. OR for the highest-rank wrestlers was even higher, 1.990 (95 % CI 1.195–3.313). These results suggest directed genetic selection in the А-allele carriers of the EPAS1 gene among sambo practitioners
Power Series Solution for Solving Nonlinear Burgers-Type Equations
Power series solution method has been traditionally used to solve ordinary and partial linear differential equations. However, despite their usefulness the application of this method has been limited to this particular kind of equations. In this work we use the method of power series to solve nonlinear partial differential equations. The method is applied to solve three versions of nonlinear time-dependent Burgers-type differential equations in order to demonstrate its scope and applicability
Covariant gauge-natural conservation laws
When a gauge-natural invariant variational principle is assigned, to
determine {\em canonical} covariant conservation laws, the vertical part of
gauge-natural lifts of infinitesimal principal automorphisms -- defining
infinitesimal variations of sections of gauge-natural bundles -- must satisfy
generalized Jacobi equations for the gauge-natural invariant Lagrangian. {\em
Vice versa} all vertical parts of gauge-natural lifts of infinitesimal
principal automorphisms which are in the kernel of generalized Jacobi morphisms
are generators of canonical covariant currents and superpotentials. In
particular, only a few gauge-natural lifts can be considered as {\em canonical}
generators of covariant gauge-natural physical charges.Comment: 16 pages; presented at XXXVI Symposium on Math. Phys., Torun
09/06-12/06/04; the last paragraph of Section 3 has been reformulated, in
particular a mistake in the equation governing the vertical part of
gauge-natural lifts with respect to prolongations of principal connections
(appearing e.g. in the vertical superpotential) has been correcte
The Lie derivative of spinor fields: theory and applications
Starting from the general concept of a Lie derivative of an arbitrary
differentiable map, we develop a systematic theory of Lie differentiation in
the framework of reductive G-structures P on a principal bundle Q. It is shown
that these structures admit a canonical decomposition of the pull-back vector
bundle i_P^*(TQ) = P\times_Q TQ over P. For classical G-structures, i.e.
reductive G-subbundles of the linear frame bundle, such a decomposition defines
an infinitesimal canonical lift. This lift extends to a prolongation
Gamma-structure on P. In this general geometric framework the concept of a Lie
derivative of spinor fields is reviewed. On specializing to the case of the
Kosmann lift, we recover Kosmann's original definition. We also show that in
the case of a reductive G-structure one can introduce a "reductive Lie
derivative" with respect to a certain class of generalized infinitesimal
automorphisms, and, as an interesting by-product, prove a result due to
Bourguignon and Gauduchon in a more general manner. Next, we give a new
characterization as well as a generalization of the Killing equation, and
propose a geometric reinterpretation of Penrose's Lie derivative of "spinor
fields". Finally, we present an important application of the theory of the Lie
derivative of spinor fields to the calculus of variations.Comment: 28 pages, 1 figur
Lagrangian reductive structures on gauge-natural bundles
A reductive structure is associated here with Lagrangian canonically defined
conserved quantities on gauge-natural bundles. Parametrized transformations
defined by the gauge-natural lift of infinitesimal principal automorphisms
induce a variational sequence such that the generalized Jacobi morphism is
naturally self-adjoint. As a consequence, its kernel defines a reductive split
structure on the relevant underlying principal bundle.Comment: 11 pages, remarks and comments added, this version published in ROM
A Guide to Precision Calculations in Dyson's Hierarchical Scalar Field Theory
The goal of this article is to provide a practical method to calculate, in a
scalar theory, accurate numerical values of the renormalized quantities which
could be used to test any kind of approximate calculation. We use finite
truncations of the Fourier transform of the recursion formula for Dyson's
hierarchical model in the symmetric phase to perform high-precision
calculations of the unsubtracted Green's functions at zero momentum in
dimension 3, 4, and 5. We use the well-known correspondence between statistical
mechanics and field theory in which the large cut-off limit is obtained by
letting beta reach a critical value beta_c (with up to 16 significant digits in
our actual calculations). We show that the round-off errors on the magnetic
susceptibility grow like (beta_c -beta)^{-1} near criticality. We show that the
systematic errors (finite truncations and volume) can be controlled with an
exponential precision and reduced to a level lower than the numerical errors.
We justify the use of the truncation for calculations of the high-temperature
expansion. We calculate the dimensionless renormalized coupling constant
corresponding to the 4-point function and show that when beta -> beta_c, this
quantity tends to a fixed value which can be determined accurately when D=3
(hyperscaling holds), and goes to zero like (Ln(beta_c -beta))^{-1} when D=4.Comment: Uses revtex with psfig, 31 pages including 15 figure
New Cases of Universality Theorem for Gravitational Theories
The "Universality Theorem" for gravity shows that f(R) theories (in their
metric-affine formulation) in vacuum are dynamically equivalent to vacuum
Einstein equations with suitable cosmological constants. This holds true for a
generic (i.e. except sporadic degenerate cases) analytic function f(R) and
standard gravity without cosmological constant is reproduced if f is the
identity function (i.e. f(R)=R). The theorem is here extended introducing in
dimension 4 a 1-parameter family of invariants R' inspired by the
Barbero-Immirzi formulation of GR (which in the Euclidean sector includes also
selfdual formulation). It will be proven that f(R') theories so defined are
dynamically equivalent to the corresponding metric-affine f(R) theory. In
particular for the function f(R)=R the standard equivalence between GR and
Holst Lagrangian is obtained.Comment: 10 pages, few typos correcte
- …