31 research outputs found
Chaos and Quantum-Classical Correspondence via Phase Space Distribution Functions
Quantum-classical correspondence in conservative chaotic Hamiltonian systems
is examined using a uniform structure measure for quantal and classical phase
space distribution functions. The similarities and differences between quantum
and classical time-evolving distribution functions are exposed by both
analytical and numerical means. The quantum-classical correspondence of
low-order statistical moments is also studied. The results shed considerable
light on quantum-classical correspondence.Comment: 16 pages, 5 figures, to appear in Physical Review
Magnetic monopoles from gauge theory phase transitions
Thermal fluctuations of the gauge field lead to monopole formation at the
grand unified phase transition in the early Universe, even if the transition is
merely a smooth crossover. The dependence of the produced monopole density on
various parameters is qualitatively different from theories with global
symmetries, and the monopoles have a positive correlation at short distances.
The number density of monopoles may be suppressed if the grand unified symmetry
is only restored for a short time by, for instance, nonthermal symmetry
restoration after preheating.Comment: 5 pages, updated to match the version published in PRD
(http://link.aps.org/abstract/PRD/v68/e021301) on 11 July 200
Out-of-equilibrium quantum fields with conserved charge
We study the out-of-equilibrium evolution of an O(2)-invariant scalar field
in which a conserved charge is stored. We apply a loop expansion of the
2-particle irreducible effective action to 3-loop order. Equations of motion
are derived which conserve both total charge and total energy yet allow for the
effects of scattering whereby charge and energy can transfer between modes.
Working in (1+1)-dimensions we solve the equations of motion numerically for a
system knocked out of equilibrium by a sudden temperature quench. We examine
the initial stages of the charge and energy redistribution. This provides a
basis from which we can understand the formation of Bose-Einstein condensates
from first principles.Comment: 11 pages, 5 figures, replacement with improved presentatio
Explaining LSND by a decaying sterile neutrino
We propose an explanation of the LSND evidence for electron antineutrino
appearance based on neutrino decay. We introduce a heavy neutrino, which is
produced in pion and muon decays because of a small mixing with muon neutrinos,
and then decays into a scalar particle and a light neutrino, predominantly of
the electron type. We require values of few eV, being the
neutrino--scalar coupling and the heavy neutrino mass, e.g. in the
range from 1 keV to 1 MeV and . Performing a fit to
the LSND data as well as all relevant null-result experiments, we show that all
data can be explained within this decay scenario. In the minimal version of the
decay model, we predict a signal in the upcoming MiniBooNE experiment
corresponding to a transition probability of the same order as seen in LSND. In
addition, we show that extending our model to two nearly degenerate heavy
neutrinos it is possible to introduce CP violation in the decay, which can lead
to a suppression of the signal in MiniBooNE running in the neutrino mode. We
briefly discuss signals in future neutrino oscillation experiments, we show
that our scenario is compatible with bounds from laboratory experiments, and we
comment on implications in astrophysics and cosmology.Comment: 23 pages, 5 figures, minor improvements, matches published versio
Mixedness and entanglement for two-mode Gaussian states
We analytically exploit the two-mode Gaussian states nonunitary dynamics. We
show that in the zero temperature limit, entanglement sudden death (ESD) will
always occur for symmetric states (where initial single mode compression is
) provided the two mode squeezing satisfies We also give the analytical expressions for the time of ESD.
Finally, we show the relation between the single modes initial impurities and
the initial entanglement, where we exhibit that the later is suppressed by the
former.Comment: Accepted for publication in Optics Communication
Non-Abelian Dark Sectors and Their Collider Signatures
Motivated by the recent proliferation of observed astrophysical anomalies,
Arkani-Hamed et al. have proposed a model in which dark matter is charged under
a non-abelian "dark" gauge symmetry that is broken at ~ 1 GeV. In this paper,
we present a survey of concrete models realizing such a scenario, followed by a
largely model-independent study of collider phenomenology relevant to the
Tevatron and the LHC. We address some model building issues that are easily
surmounted to accommodate the astrophysics. While SUSY is not necessary, we
argue that it is theoretically well-motivated because the GeV scale is
automatically generated. Specifically, we propose a novel mechanism by which
mixed D-terms in the dark sector induce either SUSY breaking or a super-Higgs
mechanism precisely at a GeV. Furthermore, we elaborate on the original
proposal of Arkani-Hamed et al. in which the dark matter acts as a messenger of
gauge mediation to the dark sector. In our collider analysis we present
cross-sections for dominant production channels and lifetime estimates for
primary decay modes. We find that dark gauge bosons can be produced at the
Tevatron and the LHC, either through a process analogous to prompt photon
production or through a rare Z decay channel. Dark gauge bosons will decay back
to the SM via "lepton jets" which typically contain >2 and as many as 8
leptons, significantly improving their discovery potential. Since SUSY decays
from the MSSM will eventually cascade down to these lepton jets, the discovery
potential for direct electroweak-ino production may also be improved.
Exploiting the unique kinematics, we find that it is possible to reconstruct
the mass of the MSSM LSP. We also present decay channels with displaced
vertices and multiple leptons with partially correlated impact parameters.Comment: 44 pages, 25 figures, version published in JHE
R-parity preserving super-WIMP decays
We point out that when the decay of one electroweak scale super-WIMP state to
another occurs at second order in a super-weak coupling constant, this can
naturally lead to decay lifetimes that are much larger than the age of the
Universe, and create observable consequences for the indirect detection of dark
matter. We demonstrate this in a supersymmetric model with Dirac neutrinos,
where the right-handed scalar neutrinos are the lightest and next-to-lightest
supersymmetric partners. We show that this model produces a super-WIMP decay
rate scaling as m_nu^4/(weak scale)^3, and may significantly enhance the
fraction of energetic electrons and positrons over anti-protons in the decay
products. Such a signature is consistent with the observations recently
reported by the PAMELA experiment.Comment: 14 pages, v3 JHEP versio
Dark matter and sub-GeV hidden U(1) in GMSB models
Motivated by the recent PAMELA and ATIC data, one is led to a scenario with
heavy vector-like dark matter in association with a hidden sector
below GeV scale. Realizing this idea in the context of gauge mediated
supersymmetry breaking (GMSB), a heavy scalar component charged under
is found to be a good dark matter candidate which can be searched for direct
scattering mediated by the Higgs boson and/or by the hidden gauge boson. The
latter turns out to put a stringent bound on the kinetic mixing parameter
between and : . For the typical range
of model parameters, we find that the decay rates of the ordinary lightest
neutralino into hidden gauge boson/gaugino and photon/gravitino are comparable,
and the former decay mode leaves displaced vertices of lepton pairs and missing
energy with distinctive length scale larger than 20 cm for invariant lepton
pair mass below 0.5 GeV. An unsatisfactory aspect of our model is that the
Sommerfeld effect cannot raise the galactic dark matter annihilation by more
than 60 times for the dark matter mass below TeV.Comment: 1+15 pages, 4 figures, version published in JCAP, references added,
minor change