1,081 research outputs found
Precise MS-bar light-quark masses from lattice QCD in the RI/SMOM scheme
We compute the conversion factors needed to obtain the MS-bar and RGI up,
down, and strange-quark masses at next-to-next-to-leading order from the
corresponding parameters renormalized in the recently proposed RI/SMOM and
RI/SMOM_gamma_mu renormalization schemes. This is important for obtaining the
MS-bar masses with the best possible precision from numerical lattice-QCD
simulations, because the customary RI(')/MOM scheme is afflicted with large
irreducible uncertainties both on the lattice and in perturbation theory. We
find that the smallness of the known one-loop matching coefficients is
accompanied by even smaller two-loop contributions. From a study of residual
scale dependences, we estimate the resulting perturbative uncertainty on the
light-quark masses to be about 2% in the RI/SMOM scheme and about 3% in the
RI/SMOM_gamma_mu scheme. Our conversion factors are given in fully analytic
form, for general covariant gauge and renormalization point. We provide
expressions for the associated anomalous dimensions.Comment: Added results for the RI/SMOM_gamma_mu scheme and anomalous
dimensions; typos fixed (results unchanged); added reference
Fractional Generalization of Gradient Systems
We consider a fractional generalization of gradient systems. We use
differential forms and exterior derivatives of fractional orders. Examples of
fractional gradient systems are considered. We describe the stationary states
of these systems.Comment: 11 pages, LaTe
Psi-Series Solution of Fractional Ginzburg-Landau Equation
One-dimensional Ginzburg-Landau equations with derivatives of noninteger
order are considered. Using psi-series with fractional powers, the solution of
the fractional Ginzburg-Landau (FGL) equation is derived. The leading-order
behaviours of solutions about an arbitrary singularity, as well as their
resonance structures, have been obtained. It was proved that fractional
equations of order with polynomial nonlinearity of order have the
noninteger power-like behavior of order near the singularity.Comment: LaTeX, 19 pages, 2 figure
Renormalization constants and beta functions for the gauge couplings of the Standard Model to three-loop order
We compute the beta functions for the three gauge couplings of the Standard
Model in the minimal subtraction scheme to three loops. We take into account
contributions from all sectors of the Standard Model. The calculation is
performed using both Lorenz gauge in the unbroken phase of the Standard Model
and background field gauge in the spontaneously broken phase. Furthermore, we
describe in detail the treatment of and present the automated setup
which we use for the calculation of the Feynman diagrams. It starts with the
generation of the Feynman rules and leads to the bare result for the Green's
function of a given process.Comment: 44 pages, 9 figures; v2: sign in eq.(29) corrected; final result
unchange
Fractional Liouville and BBGKI Equations
We consider the fractional generalizations of Liouville equation. The
normalization condition, phase volume, and average values are generalized for
fractional case.The interpretation of fractional analog of phase space as a
space with fractal dimension and as a space with fractional measure are
discussed. The fractional analogs of the Hamiltonian systems are considered as
a special class of non-Hamiltonian systems. The fractional generalization of
the reduced distribution functions are suggested. The fractional analogs of the
BBGKI equations are derived from the fractional Liouville equation.Comment: 20 page
Pure Stationary States of Open Quantum Systems
Using Liouville space and superoperator formalism we consider pure stationary
states of open and dissipative quantum systems. We discuss stationary states of
open quantum systems, which coincide with stationary states of closed quantum
systems. Open quantum systems with pure stationary states of linear oscillator
are suggested. We consider stationary states for the Lindblad equation. We
discuss bifurcations of pure stationary states for open quantum systems which
are quantum analogs of classical dynamical bifurcations.Comment: 7p., REVTeX
Universal Electromagnetic Waves in Dielectric
The dielectric susceptibility of a wide class of dielectric materials
follows, over extended frequency ranges, a fractional power-law frequency
dependence that is called the "universal" response. The electromagnetic fields
in such dielectric media are described by fractional differential equations
with time derivatives of non-integer order. An exact solution of the fractional
equations for a magnetic field is derived. The electromagnetic fields in the
dielectric materials demonstrate fractional damping. The typical features of
"universal" electromagnetic waves in dielectric are common to a wide class of
materials, regardless of the type of physical structure, chemical composition,
or of the nature of the polarizing species, whether dipoles, electrons or ions.Comment: 19 pages, LaTe
Fractional Systems and Fractional Bogoliubov Hierarchy Equations
We consider the fractional generalizations of the phase volume, volume
element and Poisson brackets. These generalizations lead us to the fractional
analog of the phase space. We consider systems on this fractional phase space
and fractional analogs of the Hamilton equations. The fractional generalization
of the average value is suggested. The fractional analogs of the Bogoliubov
hierarchy equations are derived from the fractional Liouville equation. We
define the fractional reduced distribution functions. The fractional analog of
the Vlasov equation and the Debye radius are considered.Comment: 12 page
Variability of the Halpha emission of Cygnus X-1 and its connection with the soft X-ray radiation
High-resolution Halpha monitoring of Cyg X-1, HD226868 was carried out during
1996-2002 and the resultant spectra analysed in conjunction with 1.5-12 keV
X-ray monitoring. We demonstrate that the Halpha line-profiles have complex
variability on different timescales, controlled in particular by the orbital
period and the focused wind model of mass loss. We find that long-term
variability of the mass loss by the supergiant and short-term variability due
to clumpy structure of the stellar wind dominate during the low/hard X-ray
state and that X-ray photoionization has a relatively small influence on the
line-profile shape and EW variability. During the high/soft X-ray state and
flaring the effect of photoionization the line-profile and EW of Halpha
increases but is still unable to describe the loose anti-correlation between EW
and the low energy X-ray emission. We propose that variability of the mass loss
by the supergiant can change wind velocities in the Stromgren zone around the
accretion disc of the secondary, leading to an increase in accretion rate
through the disc.Comment: Accepted for publication in A&
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