860 research outputs found
Transverse velocities, intermittency and asymmetry in fully developed turbulence
Using experimental transverse velocities data for very high Reynolds number
turbulence, we suggest a model describing both formation of intermittency and
asymmetry of turbulence. The model, called "bump-model" is a modification of
ramp-model suggested earlier, S.I. Vainshtein and K.R. Sreenivasan, Phys. Rev.
Lett., 73, 3085 (1994). The connection between asymmetry and intermittency
makes it possible to study the latter with relatively low moments.Comment: 3 pages, 2 figure
Masses and decay constants of bound states containing fourth family quarks from QCD sum rules
The heavy fourth generation of quarks that have sufficiently small mixing
with the three known SM families form hadrons. In the present work, we
calculate the masses and decay constants of mesons containing either both
quarks from the fourth generation or one from fourth family and the other from
known third family SM quarks in the framework of the QCD sum rules. In the
calculations, we take into account two gluon condensate diagrams as
nonperturbative contributions. The obtained results reduce to the known masses
and decay constants of the and quarkonia when the fourth
family quark is replaced by the bottom or charm quark.Comment: 15 Pages, 9 Figures and 6 Table
Magnetized Turbulent Dynamo in Protogalaxies
The prevailing theory for the origin of cosmic magnetic fields is that they
have been amplified to their present values by the turbulent dynamo inductive
action in the protogalactic and galactic medium. Up to now, in calculation of
the turbulent dynamo, it has been customary to assume that there is no back
reaction of the magnetic field on the turbulence, as long as the magnetic
energy is less than the turbulent kinetic energy. This assumption leads to the
kinematic dynamo theory. However, the applicability of this theory to
protogalaxies is rather limited. The reason is that in protogalaxies the
temperature is very high, and the viscosity is dominated by magnetized ions. As
the magnetic field strength grows in time, the ion cyclotron time becomes
shorter than the ion collision time, and the plasma becomes strongly
magnetized. As a result, the ion viscosity becomes the Braginskii viscosity.
Thus, in protogalaxies the back reaction sets in much earlier, at field
strengths much lower than those which correspond to field-turbulence energy
equipartition, and the turbulent dynamo becomes what we call the magnetized
turbulent dynamo. In this paper we lay the theoretical groundwork for the
magnetized turbulent dynamo. In particular, we predict that the magnetic energy
growth rate in the magnetized dynamo theory is up to ten time larger than that
in the kinematic dynamo theory. We also briefly discuss how the Braginskii
viscosity can aid the development of the inverse cascade of magnetic energy
after the energy equipartition is reached.Comment: accepted to ApJ, 35 pages, 3 figure
New physics in \epsilon' from chromomagnetic contributions and limits on Left-Right symmetry
New physics in the chromomagnetic flavor changing transition s->dg* can avoid
the strong GIM suppression of the Standard Model and lead to large
contributions to CP-violating observables, in particular to the epsilon'
parameter, that we address here. We discuss the case of the Left-Right
symmetric models, where this contribution implies bounds on the phases of the
right-handed quark mixing matrix, or in generic models with large phases a
strong bound on the Left-Right symmetry scale. To the leading order, a numeric
formula for epsilon' as a function of the short-distance coefficients for a
wide class of models of new physics is given.Comment: 12 pages, Eq. 12 and related numerics amende
Compressible hydromagnetic nonlinearities in the predecoupling plasma
The adiabatic inhomogeneities of the scalar curvature lead to a compressible
flow affecting the dynamics of the hydromagnetic nonlinearities. The influence
of the plasma on the evolution of a putative magnetic field is explored with
the aim of obtaining an effective description valid for sufficiently large
scales. The bulk velocity of the plasma, computed in the framework of the
LambdaCDM scenario, feeds back into the evolution of the magnetic power spectra
leading to a (nonlocal) master equation valid in Fourier space and similar to
the ones discussed in the context of wave turbulence. Conversely, in physical
space, the magnetic power spectra obey a Schroedinger-like equation whose
effective potential depends on the large-scale curvature perturbations.
Explicit solutions are presented both in physical space and in Fourier space.
It is argued that curvature inhomogeneities, compatible with the WMAP 7yr data,
shift to lower wavenumbers the magnetic diffusivity scale.Comment: 29 page
Evidence for topological nonequilibrium in magnetic configurations
We use direct numerical simulations to study the evolution, or relaxation, of
magnetic configurations to an equilibrium state. We use the full single-fluid
equations of motion for a magnetized, non-resistive, but viscous fluid; and a
Lagrangian approach is used to obtain exact solutions for the magnetic field.
As a result, the topology of the magnetic field remains unchanged, which makes
it possible to study the case of topological nonequilibrium. We find two cases
for which such nonequilibrium appears, indicating that these configurations may
develop singular current sheets.Comment: 10 pages, 5 figure
Custodial bulk Randall-Sundrum model and B->K* l+ l'-
The custodial Randall-Sundrum model based on SU(2)_L X SU(2)_R X U(1)_(B-L)
generates new flavor-changing-neutral-current (FCNC) phenomena at tree level,
mediated by Kaluza-Klein neutral gauge bosons. Based on two natural assumptions
of universal 5D Yukawa couplings and no-cancellation in explaining the observed
standard model fermion mixing matrices, we determine the bulk Dirac mass
parameters. Phenomenological constraints from lepton-flavor-violations are also
used to specify the model. From the comprehensive study of B->K* l+ l'-, we
found that only the B->K*ee decay has sizable new physics effects. The zero
value position of the forward-backward asymmetry in this model is also
evaluated, with about 5% deviation from the SM result. Other effective
observables are also suggested such as the ratio of two differential (or
partially integrated) decay rates of B->K*ee and B->K*mu mu. For the first KK
gauge boson mass of M_A^(1)=2-4 TeV, we can have about 10-20% deviation from
the SM results.Comment: references added with minor change
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