308 research outputs found
Finite to infinite steady state solutions, bifurcations of an integro-differential equation
We consider a bistable integral equation which governs the stationary
solutions of a convolution model of solid--solid phase transitions on a circle.
We study the bifurcations of the set of the stationary solutions as the
diffusion coefficient is varied to examine the transition from an infinite
number of steady states to three for the continuum limit of the
semi--discretised system. We show how the symmetry of the problem is
responsible for the generation and stabilisation of equilibria and comment on
the puzzling connection between continuity and stability that exists in this
problem
On the unitarity of higher-dervative and nonlocal theories
We consider two simple models of higher-derivative and nonlocal quantu
systems.It is shown that, contrary to some claims found in literature, they can
be made unitary.Comment: 8 pages, no figure
Linearisation of Universal Field Equations
The Universal Field Equations, recently constructed as examples of higher
dimensional dynamical systems which admit an infinity of inequivalent
Lagrangians are shown to be linearised by a Legendre transformation. This
establishes the conjecture that these equations describe integrable systems.
While this construction is implicit in general, there exists a large class of
solutions for which an explicit form may be written.Comment: 11pp., DTP-92/47, NI-92/01
Covariant scalar representation of quantization of the scalar relativistic particle
A covariant scalar representation of is constructed and
analysed in comparison with existing methods for the quantization of the scalar
relativistic particle. It is found that, with appropriately defined
wavefunctions, this produced representation can be identified
with the state space arising from the canonical BFV-BRST quantization of the
modular invariant, unoriented scalar particle (or antiparticle) with admissible
gauge fixing conditions. For this model, the cohomological determination of
physical states can thus be obtained purely from the representation theory of
the algebra.Comment: 16 pages Late
On singular Lagrangians affine in velocities
The properties of Lagrangians affine in velocities are analyzed in a
geometric way. These systems are necessarily singular and exhibit, in general,
gauge invariance. The analysis of constraint functions and gauge symmetry leads
us to a complete classification of such Lagrangians.Comment: AMSTeX, 22 page
Radiative correction of the correlator for (0^{++},1) light hybrid
We calculate the radiative corrections to the current-current correlator of
the hybrid current . Based on this
new result we use the QCD sum rule approach to estimate lower bounds on the
masses of the = and light hybrids.Comment: References added and Text improve
A Precision Measurement of Nuclear Muon Capture on 3He
The muon capture rate in the reaction mu- 3He -> nu + 3H has been measured at
PSI using a modular high pressure ionization chamber. The rate corresponding to
statistical hyperfine population of the mu-3He atom is (1496.0 +- 4.0) s^-1.
This result confirms the PCAC prediction for the pseudoscalar form factors of
the 3He-3H system and the nucleon.Comment: 13 pages, 6 PostScript figure
Equilibrium states and chaos in an oscillating double-well potential
We investigate numerically parametrically driven coupled nonlinear Schrödinger equations modeling the dynamics of coupled wave fields in a periodically oscillating double-well potential. The equations describe, among other things, two coupled periodically curved optical waveguides with Kerr nonlinearity or Bose-Einstein condensates in a double-well potential that is shaken horizontally and periodically in time. In particular, we study the persistence of equilibrium states of the undriven system due to the presence of the parametric drive. Using numerical continuations of periodic orbits and calculating the corresponding Floquet multipliers, we find that the drive can (de)stabilize a continuation of an equilibrium state indicated by the change in the (in)stability of the orbit, showing that parametric drives can provide a powerful control to nonlinear (optical- or matter-wave-) field tunneling. We also discuss the appearance of chaotic regions reported in previous studies that is due to destabilization of a periodic orbit. Analytical approximations based on an averaging method are presented. Using perturbation theory, the influence of the drive on the symmetry-breaking bifurcation point is analyzed. © 2014 American Physical Society
Harmonic BRST Quantization of Systems with Irreducible Holomorphic Boson and Fermion Constraints
We show that the harmonic Becchi-Rouet-Stora-Tyutin method of quantizing
bosonic systems with second-class constraints or first-class holomorphic
constraints extends to systems having both bosonic and fermionic second-class
or first-class holomorphic constraints. Using a limit argument, we show that
the harmonic BRST modified path integral reproduces the correct Senjanovic
measure.Comment: 11 pages, phyzz
Three-Nucleon Electroweak Capture Reactions
Recent advances in the study of the p-d radiative and mu-3he weak capture
processes are presented and discussed. The three-nucleon bound and scattering
states are obtained using the correlated-hyperspherical-harmonics method, with
realistic Hamiltonians consisting of the Argonne v14 or Argonne v18 two-nucleon
and Tucson-Melbourne or Urbana IX three-nucleon interactions. The
electromagnetic and weak transition operators include one- and two-body
contributions. The theoretical accuracy achieved in these calculations allows
for interesting comparisons with experimental data.Comment: 12 pages, 4 figures, invited talk at the CFIF Fall Workshop: Nuclear
Dynamics, from Quarks to Nuclei, Lisbon, 31st of October - 1st of November
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