292 research outputs found
Microcanonical Ensemble and Algebra of Conserved Generators for Generalized Quantum Dynamics
It has recently been shown, by application of statistical mechanical methods
to determine the canonical ensemble governing the equilibrium distribution of
operator initial values, that complex quantum field theory can emerge as a
statistical approximation to an underlying generalized quantum dynamics. This
result was obtained by an argument based on a Ward identity analogous to the
equipartition theorem of classical statistical mechanics. We construct here a
microcanonical ensemble which forms the basis of this canonical ensemble. This
construction enables us to define the microcanonical entropy and free energy of
the field configuration of the equilibrium distribution and to study the
stability of the canonical ensemble. We also study the algebraic structure of
the conserved generators from which the microcanonical and canonical ensembles
are constructed, and the flows they induce on the phase space.Comment: Plain TeX, 18 pages. Corrected report number onl
Spectral Function of Fermion Coupled with Massive Vector Boson at Finite Temperature in Gauge Invariant Formalism
We investigate spectral properties of a fermion coupled with a massive gauge
boson with a mass m at finite temperature (T) in the perturbation theory. The
massive gauge boson is introduced as a U(1) gauge boson in the Stueckelberg
formalism with a gauge parameter \alpha. We find that the fermion spectral
function has a three-peak structure for T \sim m irrespective of the choice of
the gauge parameter, while it tends to have one faint peak at the origin and
two peaks corresponding to the normal fermion and anti-plasmino excitations
familiar in QED in the hard thermal loop approximation for T \gg m. We show
that our formalism successfully describe the fermion spectral function in the
whole T region with the correct high-T limit except for the faint peak at the
origin, although some care is needed for choice of the gauge parameter for T
\gg m. We clarify that for T \sim m, the fermion pole is almost independent of
the gauge parameter in the one-loop order, while for T \gg m, the one-loop
analysis is valid only for \alpha \ll 1/g where g is the fermion-boson coupling
constant, implying that the one-loop analysis can not be valid for large gauge
parameters as in the unitary gauge.Comment: 28pages, 11figures. v2: typos fixe
Geometrical approach to the proton spin decomposition
We discuss in detail and from the geometrical point of view the issues of
gauge invariance and Lorentz covariance raised by the approach proposed
recently by Chen et al. to the proton spin decomposition. We show that the
gauge invariance of this approach follows from a mechanism similar to the one
used in the famous Stueckelberg trick. Stressing the fact that the Lorentz
symmetry does not force the gauge potential to transform as a Lorentz
four-vector, we show that the Chen et al. approach is Lorentz covariant
provided that one uses the suitable Lorentz transformation law. We also make an
attempt to summarize the present situation concerning the proton spin
decomposition. We argue that the ongoing debates concern essentially the
physical interpretation and are due to the plurality of the adopted pictures.
We discuss these different pictures and propose a pragmatic point of view.Comment: 39 pages, 1 figure, updated version to appear in PRD (2013
The Supersymmetric Stueckelberg Mass and Overcoming the Fayet-Iliopoulos Mechanism for Breaking Symmetry
Gauge invariant generation of mass for supersymmetric U(1) vector field
through use of a chiral Stueckelberg superfield is considered. When a
Fayet-Iliopoulos D term is also present, no breaking of supersymmetry ever
occurs so long as the Stueckelberg mass is not zero. A moduli space in which
gauge symmetry is spontaneously broken arises in this case
LHC signatures for Z` models with continuously distributed mass
We discuss phenomenological consequences of renormalizable Z` models with
continuously distributed mass. We point out that one of possible LHC signatures
for such nodel is the existence of broad resonance in Drell-Yan reaction .Comment: 7 page
A Supersymmetric U(1)' Model with Multiple Dark Matters
We consider a scenario where a supersymmetric model has multiple dark matter
particles. Adding a U(1)' gauge symmetry is a well-motivated extension of the
Minimal Supersymmetric Standard Model (MSSM). It can cure the problems of the
MSSM such as the mu-problem or the proton decay problem with high-dimensional
lepton number and baryon number violating operators which R-parity allows. An
extra parity (U-parity) may arise as a residual discrete symmetry after U(1)'
gauge symmetry is spontaneously broken. The Lightest U-parity Particle (LUP) is
stable under the new parity becoming a new dark matter candidate. Up to three
massive particles can be stable in the presence of the R-parity and the
U-parity. We numerically illustrate that multiple stable particles in our model
can satisfy both constraints from the relic density and the direct detection,
thus providing a specific scenario where a supersymmetric model has
well-motivated multiple dark matters consistent with experimental constraints.
The scenario provides new possibilities in the present and upcoming dark matter
searches in the direct detection and collider experiments.Comment: 25 pages, 5 figure
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