19,971 research outputs found
Effect of helicity and rotation on the free decay of turbulent flows
The self-similar decay of energy in a turbulent flow is studied in direct
numerical simulations with and without rotation. Two initial conditions are
considered: one non-helical (mirror-symmetric), and one with maximal helicity.
The results show that, while in the absence of rotation the energy in the
helical and non-helical cases decays with the same rate, in rotating flows the
helicity content has a major impact on the decay rate. These differences are
associated with differences in the energy and helicity cascades when rotation
is present. Properties of the structures that arise in the flow at late times
in each time are also discussed.Comment: 4 pages, 4 figure
Reconstructing Seesaws
We explore some aspects of "reconstructing" the heavy singlet sector of
supersymmetric type I seesaw models, for two, three or four singlets. We work
in the limit where one light neutrino is massless. In an ideal world, where
selected coefficients of the TeV-scale effective Lagrangian could be measured
with arbitrary accuracy, the two-singlet case can be reconstructed, two three
or more singlets can be differentiated, and an inverse seesaw with four
singlets can be reconstructed. In a more realistic world, we estimate \ell_\a
\to \ell_\b \gamma expectations with a "Minimal-Flavour-Violation-like"
ansatz, which gives a relation between ratios of the three branching ratios.
The two singlet model predicts a discrete set of ratios.Comment: 14 page
Optically-Induced Polarons in Bose-Einstein Condensates: Monitoring Composite Quasiparticle Decay
Nonresonant light-scattering off atomic Bose-Einstein condensates (BECs) is
predicted to give rise to hitherto unexplored composite quasiparticles:
unstable polarons, i.e., local ``impurities'' dressed by virtual phonons.
Optical monitoring of their spontaneous decay can display either Zeno or
anti-Zeno deviations from the Golden Rule, and thereby probe the temporal
correlations of elementary excitations in BECs.Comment: 4 pages, 3 figure
Relating Leptogenesis to Low Energy Flavor Violating Observables in Models with Spontaneous CP Violation
In the minimal left-right symmetric model, there are only two intrinsic CP
violating phases to account for all CP violation in both the quark and lepton
sectors, if CP is broken spontaneously by the complex phases in the VEV's of
the scalar fields. In addition, the left- and right-handed Majorana mass terms
for the neutrinos are proportional to each other due to the parity in the
model. This is thus a very constrained framework, making the existence of
correlations among the CP violation in leptogenesis, neutrino oscillation and
neutrinoless double beta decay possible. In these models, CP violation in the
leptonic sector and CP violation in the quark sector are also related. We find,
however, that such connection is rather weak due to the large hierarchy in the
bi-doublet VEV required by a realistic quark sector.Comment: RevTeX4, 21 pages; v2: references added, version to appear in Phys.
Rev.
Problems with Extraction of the Nucleon to Delta(1232) Photonic Amplitudes
We investigate the model dependence and the importance of choice of database
in extracting the {\it physical} nucleon-Delta(1232) electromagnetic transition
amplitudes, of interest to QCD and baryon structure, from the pion
photoproduction observables. The model dependence is found to be much smaller
than the range of values obtained when different datasets are fitted. In
addition, some inconsistencies in the current database are discovered, and
their affect on the extracted transition amplitudes is discussed.Comment: Revtex, 2 figs., submitted to PR
Effective Lagrangian Approach to the Fermion Mass Problem
An effective theory is proposed, combining the standard gauge group
with a horizontal discrete
symmetry. By assigning appropriate charges under this discrete symmetry to the
various fermion fields and to (at least) two Higgs doublets, the broad spread
of the fermion mass and mixing angle spectrum can be explained as a result of
suppressed, non-renormalisable terms. A particular model is constructed which
achieves the above while simultaneously suppressing neutral Higgs-induced
flavour-changing processes.Comment: 21 pages, UM-P-93/81, latex file, 1 figure available on reques
On rigidly rotating perfect fluid cylinders
The gravitational field of a rigidly rotating perfect fluid cylinder with
gamma- law equation of state is found analytically. The solution has two
parameters and is physically realistic for gamma in the interval (1.41,2].
Closed timelike curves always appear at large distances.Comment: 10 pages, Revtex (galley
Deposition And Drying Dynamics Of Liquid Crystal Droplets
Drop drying and deposition phenomena reveal a rich interplay of fundamental science and engineering, give rise to fascinating everyday effects (coffee rings), and influence technologies ranging from printing to genotyping. Here we investigate evaporation dynamics, morphology, and deposition patterns of drying lyotropic chromonic liquid crystal droplets. These drops differ from typical evaporating colloidal drops primarily due to their concentration-dependent isotropic, nematic, and columnar phases. Phase separation occurs during evaporation, and in the process creates surface tension gradients and significant density and viscosity variation within the droplet. As a result, the drying multiphase drops exhibit different convective currents, drop morphologies, and deposition patterns (coffee-rings)
Interpretations of the NuTeV
We summarize theoretical explanations of the three discrepancy
between measured by NuTeV and predicted by the Standard Model
global fit. Possible new physics explanations ({\it e.g.} an unmized ) are
not compelling. The discrepancy would be reduced by a positive momentum
asymmetry in the strange sea; present experimental estimates of are
unreliable or incomplete. Upgrading the NuTeV analysis to NLO would alleviate
concerns that the discrepancy is a QCD effect.Comment: (proceedings for the NuFact'02 Workshop); reference and footnote
added, following the NuTeV proceeding
Non-resonant leptogenesis in seesaw models with an almost conserved B-L
We review the motivations and some results on leptogenesis in seesaw models
with an almost conserved lepton number. The paper is based on a talk given at
the 5th International Symposium on Symmetries in Subatomic Physics, SSP2012.Comment: 8 pages, 1 figure. Published in the proceedings of the 5th
International Symposium on Symmetries in Subatomic Physics, SSP201
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