1,793 research outputs found
Parity violating vertices for spin-3 gauge fields
The problem of constructing consistent parity-violating interactions for
spin-3 gauge fields is considered in Minkowski space. Under the assumptions of
locality, Poincar\'e invariance and parity non-invariance, we classify all the
nontrivial perturbative deformations of the abelian gauge algebra. In
space-time dimensions and , deformations of the free theory are
obtained which make the gauge algebra non-abelian and give rise to nontrivial
cubic vertices in the Lagrangian, at first order in the deformation parameter
. At second order in , consistency conditions are obtained which the
five-dimensional vertex obeys, but which rule out the candidate.
Moreover, in the five-dimensional first order deformation case, the gauge
transformations are modified by a new term which involves the second de
Wit--Freedman connection in a simple and suggestive way.Comment: 27 pages, 1 table, revtex4, typos correcte
g = 2 as a Gauge Condition
Charged matter spin-1 fields enjoy a nonelectromagnetic gauge symmetry when
interacting with vacuum electromagnetism, provided their gyromagnetic ratio is
2.Comment: 5 pages, REVTeX, submitted to Phys Rev D Brief Report
Computational modeling of gradient hardening in polycrystals
A gradient hardening crystal plasticity model for polycrystals is introduced in Ekh et al. (2007). It is formulated in a thermodynamically consistent fashion and is capable of modeling a grain-size-dependent stress-strain response. In this contribution we extend that model to also include cross-hardening. A free energy is stated which includes contributions from the gradient of hardening along each slip direction. This leads to hardening stresses depending on the second derivative of the plastic slip. The governing equations for a nonlinear coupled system of equations is solved numerically with the help of a dual-mixed finite element method. The numerical results show that the macroscopic strength increases with decreasing grain size as a result of gradient hardening: Moreover, cross-hardening further enhances the strengthening gradient effect
Improvement of measurement accuracy in SU(1,1) interferometers
We consider an SU(1,1) interferometer employing four-wave mixers that is fed
with two-mode states which are both coherent and intelligent states of the
SU(1,1) Lie group. It is shown that the phase sensitivity of the interferometer
can be essentially improved by using input states with a large photon-number
difference between the modes.Comment: LaTeX, 5 pages, 1 figure (compressed PostScript, available at
http://www.technion.ac.il/~brif/graphics/interfer_graph/qopt.ps.gz ). More
information on http://www.technion.ac.il/~brif/science.htm
A tracking algorithm for the stable spin polarization field in storage rings using stroboscopic averaging
Polarized protons have never been accelerated to more than about GeV. To
achieve polarized proton beams in RHIC (250GeV), HERA (820GeV), and the
TEVATRON (900GeV), ideas and techniques new to accelerator physics are needed.
In this publication we will stress an important aspect of very high energy
polarized proton beams, namely the fact that the equilibrium polarization
direction can vary substantially across the beam in the interaction region of a
high energy experiment when no countermeasure is taken. Such a divergence of
the polarization direction would not only diminish the average polarization
available to the particle physics experiment, but it would also make the
polarization involved in each collision analyzed in a detector strongly
dependent on the phase space position of the interacting particle. In order to
analyze and compensate this effect, methods for computing the equilibrium
polarization direction are needed. In this paper we introduce the method of
stroboscopic averaging, which computes this direction in a very efficient way.
Since only tracking data is needed, our method can be implemented easily in
existing spin tracking programs. Several examples demonstrate the importance of
the spin divergence and the applicability of stroboscopic averaging.Comment: 39 page
Correlation Functions of Conserved Currents in Four Dimensional Conformal Field Theory
We derive a generating function for all the 3-point functions of higher spin
conserved currents in four dimensional conformal field theory. The resulting
expressions have a rather surprising factorized form which suggest that they
can all be realized by currents built from free massless fields of arbitrary
(half-)integer spin s. This property is however not necessarily true also for
the higher-point functions. As an illustration we analyze the general 4-point
function of conserved abelian U(1) currents of scale dimension equal to three
and find that apart from the two free field realizations there is a unique
possible function which may correspond to an interacting theory. Although this
function passes several non-trivial consistency tests, it remains an open
challenging problem whether it can be actually realized in an interacting CFT.Comment: 20 pages, LaTeX, references adde
(2+1)D Exotic Newton-Hooke Symmetry, Duality and Projective Phase
A particle system with a (2+1)D exotic Newton-Hooke symmetry is constructed
by the method of nonlinear realization. It has three essentially different
phases depending on the values of the two central charges. The subcritical and
supercritical phases (describing 2D isotropic ordinary and exotic oscillators)
are separated by the critical phase (one-mode oscillator), and are related by a
duality transformation. In the flat limit, the system transforms into a free
Galilean exotic particle on the noncommutative plane. The wave equations
carrying projective representations of the exotic Newton-Hooke symmetry are
constructed.Comment: 30 pages, 2 figures; typos correcte
Crystal properties of eigenstates for quantum cat maps
Using the Bargmann-Husimi representation of quantum mechanics on a torus
phase space, we study analytically eigenstates of quantized cat maps. The
linearity of these maps implies a close relationship between classically
invariant sublattices on the one hand, and the patterns (or `constellations')
of Husimi zeros of certain quantum eigenstates on the other hand. For these
states, the zero patterns are crystals on the torus. As a consequence, we can
compute explicit families of eigenstates for which the zero patterns become
uniformly distributed on the torus phase space in the limit . This
result constitutes a first rigorous example of semi-classical equidistribution
for Husimi zeros of eigenstates in quantized one-dimensional chaotic systems.Comment: 43 pages, LaTeX, including 7 eps figures Some amendments were made in
order to clarify the text, mainly in the 4 first sections. Figures are
unchanged. To be published in: Nonlinearit
Multi-Dimensional Hermite Polynomials in Quantum Optics
We study a class of optical circuits with vacuum input states consisting of
Gaussian sources without coherent displacements such as down-converters and
squeezers, together with detectors and passive interferometry (beam-splitters,
polarisation rotations, phase-shifters etc.). We show that the outgoing state
leaving the optical circuit can be expressed in terms of so-called
multi-dimensional Hermite polynomials and give their recursion and
orthogonality relations. We show how quantum teleportation of photon
polarisation can be modelled using this description.Comment: 10 pages, submitted to J. Phys. A, removed spurious fil
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