1,590 research outputs found
Contact Term, its Holographic Description in QCD and Dark Energy
In this work we study the well known contact term, which is the key element
in resolving the so-called problem in QCD. We study this term using
the dual Holographic Description. We argue that in the dual picture the contact
term is saturated by the D2 branes which can be interpreted as the tunnelling
events in Minkowski space-time. We quote a number of direct lattice results
supporting this identification. We also argue that the contact term receives a
Casimir -like correction \sim (\Lqcd R)^{-1} rather than naively expected
\exp(-\Lqcd R) when the Minkowski space-time is replaced by
a large but finite manifold with a size . Such a behaviour is consistent
with other QFT-based computations when power like corrections are due to
nontrivial properties of topological sectors of the theory. In holographic
description such a behaviour is due to massless Ramond-Ramond (RR) field living
in the bulk of multidimensional space when power like corrections is a natural
outcome of massless RR field. In many respects the phenomenon is similar to the
Aharonov -Casher effect when the "modular electric field" can penetrate into a
superconductor where the electric field is exponentially screened. The role of
"modular operator" from Aharonov -Casher effect is played by large gauge
transformation operator in 4d QCD, resulting the transparency of the
system to topologically nontrivial pure gauge configurations. We discuss some
profound consequences of our findings. In particular, we speculate that a slow
variation of the contact term in expanding universe might be the main source of
the observed Dark Energy.Comment: Final version to appear in Phys. Rev. D. Comments added on
interpretation of the "topological Casimir effect" from 5d viewpoint where it
can be thought as conventional Casimir effec
The Gauge Fields and Ghosts in Rindler Space
We consider 2d Maxwell system defined on the Rindler space with metric
ds^2=\exp(2a\xi)\cdot(d\eta^2-d\xi^2) with the goal to study the dynamics of
the ghosts. We find an extra contribution to the vacuum energy in comparison
with Minkowski space time with metric ds^2= dt^2-dx^2. This extra contribution
can be traced to the unphysical degrees of freedom (in Minkowski space). The
technical reason for this effect to occur is the property of Bogolubov's
coefficients which mix the positive and negative frequencies modes. The
corresponding mixture can not be avoided because the projections to positive
-frequency modes with respect to Minkowski time t and positive -frequency modes
with respect to the Rindler observer's proper time \eta are not equivalent. The
exact cancellation of unphysical degrees of freedom which is maintained in
Minkowski space can not hold in the Rindler space. In BRST approach this effect
manifests itself as the presence of BRST charge density in L and R parts. An
inertial observer in Minkowski vacuum |0> observes a universe with no net BRST
charge only as a result of cancellation between the two. However, the Rindler
observers who do not ever have access to the entire space time would see a net
BRST charge. In this respect the effect resembles the Unruh effect. The effect
is infrared (IR) in nature, and sensitive to the horizon and/or boundaries. We
interpret the extra energy as the formation of the "ghost condensate" when the
ghost degrees of freedom can not propagate, but nevertheless do contribute to
the vacuum energy. Exact computations in this simple 2d model support the claim
made in [1] that the ghost contribution might be responsible for the observed
dark energy in 4d FLRW universe.Comment: Final version to appear in Phys. Rev. D. Comments on relation with
energy momentum computations and few new refs are adde
Large-Scale Magnetic Fields, Dark Energy and QCD
Cosmological magnetic fields are being observed with ever increasing
correlation lengths, possibly reaching the size of superclusters, therefore
disfavouring the conventional picture of generation through primordial seeds
later amplified by galaxy-bound dynamo mechanisms. In this paper we put forward
a fundamentally different approach that links such large-scale magnetic fields
to the cosmological vacuum energy. In our scenario the dark energy is due to
the Veneziano ghost (which solves the problem in QCD). The Veneziano
ghost couples through the triangle anomaly to the electromagnetic field with a
constant which is unambiguously fixed in the standard model. While this
interaction does not produce any physical effects in Minkowski space, it
triggers the generation of a magnetic field in an expanding universe at every
epoch. The induced energy of the magnetic field is thus proportional to
cosmological vacuum energy: , hence acting as a source for the magnetic energy
. The corresponding numerical estimate leads to a magnitude in the
nG range. There are two unique and distinctive predictions of our proposal: an
uninterrupted active generation of Hubble size correlated magnetic fields
throughout the evolution of the universe; the presence of parity violation on
the enormous scales , which apparently has been already observed in CMB.
These predictions are entirely rooted into the standard model of particle
physics.Comment: jhep style, 22 pages, v2 with updated estimates and extended
discussion on parity violation, v3 as published (references updated
Systematic Review: The Effects of Nonpharmacological and Pharmacological Measures in Neonates with Neonatal Abstinence Syndrome
With the increasing incidence of drug addiction among pregnant women, neonatal abstinence syndrome (NAS) has become a significant problem in the United States and has led to increased hospital costs, longer lengths of stay, and more serious health problems in neonates. This systematic review will explore the evidence about outcome differences for neonates with NAS that receive breastfeeding, rooming-in, and acupuncture in addition to pharmacological agents when compared to infants only receiving pharmacological agents. Twenty-one articles, retrieved from the databases PubMed and CINAHL and published between the years 2000-2017, were described in an integrated review, analyzed with critical appraisal, and synthesized for this systematic review. In general, researchers have found that breastfeeding, rooming-in, and acupuncture have positive effects of decreasing the need for pharmacological treatment, NAS symptoms, hospital costs, and length of hospital stay for infants with NAS when used in conjunction with pharmacologic agents
On Classification of QCD defects via holography
We discuss classification of defects of various codimensions within a
holographic model of pure Yang-Mills theories or gauge theories with
fundamental matter. We focus on their role below and above the phase transition
point as well as their weights in the partition function. The general result is
that objects which are stable and heavy in one phase are becoming very light
(tensionless) in the other phase. We argue that the dependence of the
partition function drastically changes at the phase transition point, and
therefore it correlates with stability properties of configurations. Some
possible applications for study the QCD vacuum properties above and below phase
transition are also discussed.Comment: 21 pages, 2 figure
Molecular evidence for horizontal transmission of chelonid alphaherpesvirus 5 at green turtle (Chelonia mydas) foraging grounds in Queensland, Australia
Fibropapillomatosis (FP) is a marine turtle disease recognised by benign tumours on the skin, eyes, shell, oral cavity and/or viscera. Despite being a globally distributed disease that affects an endangered species, research on FP and its likely causative agent chelonid alphaherpesvirus 5 (ChHV5) in Australia is limited. Here we present improved molecular assays developed for detection of ChHV5, in combination with a robust molecular and phylogenetic analysis of ChHV5 variants. This approach utilised a multi-gene assay to detect ChHV5 in all FP tumors sampled from 62 marine turtles found at six foraging grounds along the Great Barrier Reef. Six distinct variants of ChHV5 were identified and the distribution of these variants was associated with host foraging ground. Conversely, no association between host genetic origin and ChHV5 viral variant was found. Together this evidence supports the hypothesis that marine turtles undergo horizontal transmission of ChHV5 at foraging grounds and are unlikely to be contracting the disease at rookeries, either during mating or vertically from parent to offspring
Suppression of inhomogeneous broadening in rf spectroscopy of optically trapped atoms
We present a novel method for reducing the inhomogeneous frequency broadening
in the hyperfine splitting of the ground state of optically trapped atoms. This
reduction is achieved by the addition of a weak light field, spatially
mode-matched with the trapping field and whose frequency is tuned in-between
the two hyperfine levels. We experimentally demonstrate the new scheme with Rb
85 atoms, and report a 50-fold narrowing of the rf spectrum
Recommended from our members
Reducing the Harm of Intimate Partner Violence: Randomized Controlled Trial of the Hampshire Constabulary CARA Experiment
Research Question: Among Southampton-area males arrested for and admitting to low-risk intimate partner violence as a first domestic offence and receiving a conditional caution, did a randomly assigned requirement to attend (with 5 to 7 other male offenders), two weekend day-long Cautioning and Relationship Abuse (CARA) workshops led by experienced professionals reduce the total severity of crime harm relative to a no-workshop control group?
Data: Eligible offenders (N =293) were randomly assigned to the CARA workshop attendance requirement (n= 154) or to the no-workshop requirement (n = 139), with 91% of all cases receiving treatment as randomly assigned. Each offender’s records of police contact were tracked for exactly 365 days after the date of random assignment.
Methods: All repeat arrests or complaints of crime naming the 293 randomly assigned offenders were coded by the Cambridge Crime Harm Index (CHI) as the primary outcome measure for each offender (Sherman et al 2016), with the sum of total days of recommended imprisonment for each offence (as the guideline starting point for sentencing) summed across all new offences, with both domestic and non-domestic relationships to their victims. Prevalence and frequency of repeat contact were also computed. All analysis was done by intention-to-treat.
Findings: Offenders assigned to the workshop group were re-arrested for crimes with a total Crime Harm Index (CHI) value that was 27% lower than for re-arrests of offenders assigned to the control group (P =.011). The CARA workshop group members were arrested for crimes totalling an average of 8.4 days of recommended imprisonment under English sentencing guidelines, compared to an average of 11.6 days per offender assigned to the control group, the equivalent of 38% more harm without the workshop than with it. The effect size was much stronger, however, in the first study period of high caseflow (72% reduction in CHI, P = .001) than in the second period (21% reduction in CHI, P =.178). Frequency of re-arrest for domestic abuse (21% lower for workshop-assigned group) and prevalence (35% lower for workshop-assigned group) also favoured the CARA workshop group.
Conclusions: The results of this one-year followup analysis suggest that the CARA workshops are an effective way to reduce the future harm of domestic abuse among first offenders who admit their crime, although effect size may vary over time. Given the highly restrictive eligibility criteria for the programme, these findings provide an evidence-based reason for testing the same treatment among a larger proportion of all first-offender arrests for domestic abuse. Keywords Intimate partner violence – policing – RCT—Crime Harm Index--CAR
Consistency, Amplitudes and Probabilities in Quantum Theory
Quantum theory is formulated as the only consistent way to manipulate
probability amplitudes. The crucial ingredient is a consistency constraint: if
there are two different ways to compute an amplitude the two answers must
agree. This constraint is expressed in the form of functional equations the
solution of which leads to the usual sum and product rules for amplitudes. A
consequence is that the Schrodinger equation must be linear: non-linear
variants of quantum mechanics are inconsistent. The physical interpretation of
the theory is given in terms of a single natural rule. This rule, which does
not itself involve probabilities, is used to obtain a proof of Born's
statistical postulate. Thus, consistency leads to indeterminism.
PACS: 03.65.Bz, 03.65.Ca.Comment: 23 pages, 3 figures (old version did not include the figures
Constraining photon-axion oscillations using quasar spectra
Using quasar spectra from the SDSS survey, we constrain the possibility of
photon-axion oscillations as a source of dimming of high redshift objects. Such
a process has been suggested as an explanation of the apparent faintness of
distant Type Ia supernovae. For most combinations of magnetic field strengths
and plasma densities along the line of sight, large beam attenuations in broad
band filters would also lead to significant differential attenuation, not
observed in the quasar sample. However, this conservative study does not
exclude the possibility of 0.1 mag dimming of Type Ia supernovae for average
plasma densities n_e = 10^(-8) cm^(-3). NIR and MIR spectroscopic studies of
high-z sources may be used put further constrains or provide indirect evidence
for the existence of a very light axion.Comment: 14 pages, 8 figure
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