311 research outputs found
Single Atom and Two Atom Ramsey Interferometry with Quantized Fields
Implications of field quantization on Ramsey interferometry are discussed and
general conditions for the occurrence of interference are obtained.
Interferences do not occur if the fields in two Ramsey zones have precise
number of photons. However in this case we show how two atom (like two photon)
interferometry can be used to discern a variety of interference effects as the
two independent Ramsey zones get entangled by the passage of first atom.
Generation of various entangled states like |0,2>+|2,0> are discussed and in
far off resonance case generation of entangled state of two coherent states is
discussed.Comment: 20 pages, 5 figures, revised version. submitted to Phys. Rev.
Supergauge interactions and electroweak baryogenesis
We present a complete treatment of the diffusion processes for supersymmetric
electroweak baryogenesis that characterizes transport dynamics ahead of the
phase transition bubble wall within the symmetric phase. In particular, we
generalize existing approaches to distinguish between chemical potentials of
particles and their superpartners. This allows us to test the assumption of
superequilibrium (equal chemical potentials for particles and sparticles) that
has usually been made in earlier studies. We show that in the Minimal
Supersymmetric Standard Model, superequilibrium is generically maintained --
even in the absence of fast supergauge interactions -- due to the presence of
Yukawa interactions. We provide both analytic arguments as well as illustrative
numerical examples. We also extend the latter to regions where analytical
approximations are not available since down-type Yukawa couplings or supergauge
interactions only incompletely equilibrate. We further comment on cases of
broken superequilibrium wherein a heavy superpartner decouples from the
electroweak plasma, causing a kinematic bottleneck in the chain of
equilibrating reactions. Such situations may be relevant for baryogenesis
within extensions of the MSSM. We also provide a compendium of inputs required
to characterize the symmetric phase transport dynamics.Comment: 49 pages, 9 figure
A Quantum-Bayesian Route to Quantum-State Space
In the quantum-Bayesian approach to quantum foundations, a quantum state is
viewed as an expression of an agent's personalist Bayesian degrees of belief,
or probabilities, concerning the results of measurements. These probabilities
obey the usual probability rules as required by Dutch-book coherence, but
quantum mechanics imposes additional constraints upon them. In this paper, we
explore the question of deriving the structure of quantum-state space from a
set of assumptions in the spirit of quantum Bayesianism. The starting point is
the representation of quantum states induced by a symmetric informationally
complete measurement or SIC. In this representation, the Born rule takes the
form of a particularly simple modification of the law of total probability. We
show how to derive key features of quantum-state space from (i) the requirement
that the Born rule arises as a simple modification of the law of total
probability and (ii) a limited number of additional assumptions of a strong
Bayesian flavor.Comment: 7 pages, 1 figure, to appear in Foundations of Physics; this is a
condensation of the argument in arXiv:0906.2187v1 [quant-ph], with special
attention paid to making all assumptions explici
Baryogenesis, Electric Dipole Moments and Dark Matter in the MSSM
We study the implications for electroweak baryogenesis (EWB) within the
minimal supersymmetric Standard Model (MSSM) of present and future searches for
the permanent electric dipole moment (EDM) of the electron, for neutralino dark
matter, and for supersymmetric particles at high energy colliders. We show that
there exist regions of the MSSM parameter space that are consistent with both
present two-loop EDM limits and the relic density and that allow for successful
EWB through resonant chargino and neutralino processes at the electroweak phase
transition. We also show that under certain conditions the lightest neutralino
may be simultaneously responsible for both the baryon asymmetry and relic
density. We give present constraints on chargino/neutralino-induced EWB implied
by the flux of energetic neutrinos from the Sun, the prospective constraints
from future neutrino telescopes and ton-sized direct detection experiments, and
the possible signatures at the Large Hadron Collider and International Linear
Collider.Comment: 32 pages, 10 figures; version to appear on JHE
Nonequilibrium evolution in scalar O(N) models with spontaneous symmetry breaking
We consider the out-of-equilibrium evolution of a classical condensate field
and its quantum fluctuations for a scalar O(N) model with spontaneously broken
symmetry. In contrast to previous studies we do not consider the large N limit,
but the case of finite N, including N=1, i.e., plain theory.
The instabilities encountered in the one-loop approximation are prevented, as
in the large-N limit, by back reaction of the fluctuations on themselves, or,
equivalently, by including a resummation of bubble diagrams.
For this resummation and its renormalization we use formulations developed
recently based on the effective action formalism of Cornwall, Jackiw and
Tomboulis. The formulation of renormalized equations for finite N derived here
represents a useful tool for simulations with realistic models. Here we
concentrate on the phase structure of such models. We observe the transition
between the spontaneously broken and the symmetric phase at low and high energy
densities, respectively. This shows that the typical structures expected in
thermal equilibrium are encountered in nonequilibrium dynamics even at early
times, i.e., before an efficient rescattering can lead to thermalization.Comment: 31 pages, 19 Figures, LaTeX; extended discussion on the basis of:
fluctuations, eff. potential, correlations, analytic calculation of
parametric resonance for "pion"_and_ "sigma" field
Hadronic Parity Violation and Inelastic Electron-Deuteron Scattering
We compute contributions to the parity-violating (PV) inelastic
electron-deuteron scattering asymmetry arising from hadronic PV. While hadronic
PV effects can be relatively important in PV threshold electro- disintegration,
we find that they are highly suppressed at quasielastic kinematics. The
interpretation of the PV quasielastic asymmetry is, thus, largely unaffected by
hadronic PV.Comment: 27 pages, 13 figures, uses REVTeX and BibTe
Identification of an age-dependent biomarker signature in children and adolescents with autism spectrum disorders
Background: Autism spectrum disorders (ASDs) are neurodevelopmental conditions with symptoms manifesting before the age of 3, generally persisting throughout life and affecting social development and com
Default Mode Network in the Effects of ¿9-Tetrahydrocannabinol (THC) on Human Executive Function
Evidence is increasing for involvement of the endocannabinoid system in cognitive functions including attention and executive function, as well as in psychiatric disorders characterized by cognitive deficits, such as schizophrenia. Executive function appears to be associated with both modulation of active networks and inhibition of activity in the default mode network. In the present study, we examined the role of the endocannabinoid system in executive function, focusing on both the associated brain network and the default mode network. A pharmacological functional magnetic resonance imaging (fMRI) study was conducted with a placebo-controlled, cross-over design, investigating effects of the endocannabinoid agonist ¿9-tetrahydrocannabinol (THC) on executive function in 20 healthy volunteers, using a continuous performance task with identical pairs. Task performance was impaired after THC administration, reflected in both an increase in false alarms and a reduction in detected targets. This was associated with reduced deactivation in a set of brain regions linked to the default mode network, including posterior cingulate cortex and angular gyrus. Less deactivation was significantly correlated with lower performance after THC. Regions that were activated by the continuous performance task, notably bilateral prefrontal and parietal cortex, did not show effects of THC. These findings suggest an important role for the endocannabinoid system in both default mode modulation and executive function. This may be relevant for psychiatric disorders associated with executive function deficits, such as schizophrenia and ADH
Molecular Sex Differences in Human Serum
Background: Sex is an important factor in the prevalence, incidence, progression, and response to treatment of many medical conditions, including autoimmune and cardiovascular diseases and psychiatric conditions. Identification of molecular differences between typical males and females can provide a valuable basis for exploring conditions differentially affected by sex. Methodology/Principal Findings: Using multiplexed immunoassays, we analyzed 174 serum molecules in 9 independent cohorts of typical individuals, comprising 196 males and 196 females. Sex differences in analyte levels were quantified using a meta-analysis approach and put into biological context using k-means to generate clusters of analytes with distinct biological functions. Natural sex differences were established in these analyte groups and these were applied to illustrate sexually dimorphic analyte expression in a cohort of 22 males and 22 females with Asperger syndrome. Reproducible sex differences were found in the levels of 77 analytes in serum of typical controls, and these comprised clusters of molecules enriched with distinct biological functions. Analytes involved in fatty acid oxidation/hormone regulation, immune cell growth and activation, and cell death were found at higher levels in females, and analytes involved in immune cell chemotaxis and other indistinct functions were higher in males. Comparison of these naturally occurring sex differences against a cohort of people with Asperger syndrome indicated that a cluster of analytes that had functions related to fatty acid oxidation/hormone regulation was associated with sex and the occurren
Galaxy and Apollo as a biologist-friendly interface for high-quality cooperative phage genome annotation
In the modern genomic era, scientists without extensive bioinformatic training need to apply
high-power computational analyses to critical tasks like phage genome annotation. At the
Center for Phage Technology (CPT), we developed a suite of phage-oriented tools housed
in open, user-friendly web-based interfaces. A Galaxy platform conducts computationally
intensive analyses and Apollo, a collaborative genome annotation editor, visualizes the
results of these analyses. The collection includes open source applications such as the
BLAST+ suite, InterProScan, and several gene callers, as well as unique tools developed at
the CPT that allow maximum user flexibility. We describe in detail programs for finding
Shine-Dalgarno sequences, resources used for confident identification of lysis genes such
as spanins, and methods used for identifying interrupted genes that contain frameshifts or
introns. At the CPT, genome annotation is separated into two robust segments that are facilitated through the automated execution of many tools chained together in an operatio
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