1,888 research outputs found
Nucleon-Nucleon Scattering in a Strong External Magnetic Field and the Neutrino Emissivity
The nucleon-nucleon scattering in a large magnetic background is considered
to find its potential to change the neutrino emissivity of the neutron stars.
For this purpose we consider the one-pion-exchange approximation to find the NN
cross-section in a background field as large as
. We show that the NN cross-section in
neutron stars with temperatures in the range 0.1-5 \texttt{MeV} can be changed
up to the one order of magnitude with respect to the one in the absence of the
magnetic field. In the limit of the soft neutrino emission the neutrino
emissivity can be written in terms of the NN scattering amplitude therefore the
large magnetic fields can dramatically change the neutrino emissivity of the
neutron stars as well.Comment: 21 pages, 5 figures, to appear in PR
Effect of tocotrienols enriched canola oil on glycemic control and oxidative status in patients with type 2 diabetes mellitus: A randomized double-blind placebo-controlled clinical trial
Background: Tocotrienols have been shown to improve glycemic control and redox balance in an animal study, but their effects on patients with diabetes are unknown. The study aimed to investigate whether tocotrienols improves glycemic control, insulin sensitivity, and oxidative stress in individuals with type 2 diabetes mellitus (T2DM). Materials and Methods: This study was a double-blinded, placebo-controlled, randomized trial. A total of 50 patients, aged 35-60 years, with T2DM treated by noninsulin hypoglycemic drugs were randomly assigned to receive either 15 mL/day tocotrienols (200 mg) enriched canola oil (n = 25) or pure canola oil (n = 25) for 8 weeks. Fasting blood sugar (FBS), fasting insulin, total antioxidant capacity (TAC), malondialdehyde (MDA), and homeostatic model assessment for insulin resistance (HOMA-IR) were determined before and after the intervention. The data were compared between and within groups, before and after the intervention. Results: Baseline characteristics of participants including age, sex, physical activity, disease duration, and type of drug consumption were not significantly different between the two groups. In tocotrienol enriched canola oil, FBS (mean percent change: �15.4 vs. 3.9; P = 0.006) and MDA (median percent change: �35.6 vs. 16.3; P = 0.003) were significantly reduced while TAC was significantly increased (median percent change: 21.4 vs. 2.3; P = 0.001) compared to pure canola oil. At the end of the study, patients who treated with tocotrienols had lower FBS (P = 0.023) and MDA (P = 0.044) compared to the pure canola oil group. However, tocotrienols had no effect on insulin concentrations and HOMA-IR. Conclusion: Tocotrienols can improve FBS concentrations and modifies redox balance in T2DM patients with poor glycemic control and can be considered in combination with hypoglycemic drugs to better control of T2DM. © 2015 Journal of Research in Medical Sciences
Positronium Hyperfine Splitting in Non-commutative Space at the Order
We obtain positronium Hyperfine Splitting owing to the non-commutativity of
space and show that, in the leading order, it is proportional to where, is the parameter of non-commutativity. It is also
shown that spatial non-commutativity splits the spacing between triplet
excited levels which provides an experimental test on
the non-commutativity of space.Comment: 7 pages, 2 figures, to appear in Phys. Rev.
Twisted supersymmetric 5D Yang-Mills theory and contact geometry
We extend the localization calculation of the 3D Chern-Simons partition
function over Seifert manifolds to an analogous calculation in five dimensions.
We construct a twisted version of N=1 supersymmetric Yang-Mills theory defined
on a circle bundle over a four dimensional symplectic manifold. The notion of
contact geometry plays a crucial role in the construction and we suggest a
generalization of the instanton equations to five dimensional contact
manifolds. Our main result is a calculation of the full perturbative partition
function on a five sphere for the twisted supersymmetric Yang-Mills theory with
different Chern-Simons couplings. The final answer is given in terms of a
matrix model. Our construction admits generalizations to higher dimensional
contact manifolds. This work is inspired by the work of Baulieu-Losev-Nekrasov
from the mid 90's, and in a way it is covariantization of their ideas for a
contact manifold.Comment: 28 pages; v2: minor mistake corrected; v3: matches published versio
Constraining noncommutative field theories with holography
An important window to quantum gravity phenomena in low energy noncommutative
(NC) quantum field theories (QFTs) gets represented by a specific form of UV/IR
mixing. Yet another important window to quantum gravity, a holography,
manifests itself in effective QFTs as a distinct UV/IR connection. In matching
these two principles, a useful relationship connecting the UV cutoff
, the IR cutoff and the scale of
noncommutativity , can be obtained. We show that an effective
QFT endowed with both principles may not be capable to fit disparate
experimental bounds simultaneously, like the muon and the masslessness of
the photon. Also, the constraints from the muon preclude any possibility
to observe the birefringence of the vacuum coming from objects at cosmological
distances. On the other hand, in NC theories without the UV completion, where
the perturbative aspect of the theory (obtained by truncating a power series in
) becomes important, a heuristic estimate of the region
where the perturbative expansion is well-defined , gets affected when holography is applied by providing the energy of the
system a -dependent lower limit. This may affect models
which try to infer the scale by using data from low-energy
experiments.Comment: 4 pages, version to be published in JHE
Neutrino-electron scattering in noncommutative space
Neutral particles can couple with the gauge field in the adjoint
representation at the tree level if the space-time coordinates are
noncommutative (NC). Considering neutrino-photon coupling in the NC QED
framework, we obtain the differential cross section of neutrino-electron
scattering. Similar to the magnetic moment effect, one of the NC terms is
proportional to , where is the electron recoil energy.
Therefore, this scattering provides a chance to achieve a stringent bound on
the NC scale in low energy by improving the sensitivity to the smaller electron
recoil energy.Comment: 12 pages, 2 figure
Three Body Bound State in Non-Commutative Space
The Bethe-Salpeter equation in non-commutative QED (NCQED) is considered for
three-body bound state. We study the non-relativistic limit of this equation in
the instantaneous approximation and derive the corresponding Schr\"{o}dinger
equation in non-commutative space. It is shown that the experimental data for
Helium atom puts an upper bound on the magnitude of the parameter of
non-commutativity, .Comment: 10 pages, 3 figures, to appear in Phys. Rev.
Exact Results in ABJM Theory from Topological Strings
Recently, Kapustin, Willett and Yaakov have found, by using localization
techniques, that vacuum expectation values of Wilson loops in ABJM theory can
be calculated with a matrix model. We show that this matrix model is closely
related to Chern-Simons theory on a lens space with a gauge supergroup. This
theory has a topological string large N dual, and this makes possible to solve
the matrix model exactly in the large N expansion. In particular, we find the
exact expression for the vacuum expectation value of a 1/6 BPS Wilson loop in
the ABJM theory, as a function of the 't Hooft parameters, and in the planar
limit. This expression gives an exact interpolating function between the weak
and the strong coupling regimes. The behavior at strong coupling is in precise
agreement with the prediction of the AdS string dual. We also give explicit
results for the 1/2 BPS Wilson loop recently constructed by Drukker and
TrancanelliComment: 18 pages, two figures, small misprints corrected and references
added, final version to appear in JHE
Direct Integration and Non-Perturbative Effects in Matrix Models
We show how direct integration can be used to solve the closed amplitudes of
multi-cut matrix models with polynomial potentials. In the case of the cubic
matrix model, we give explicit expressions for the ring of non-holomorphic
modular objects that are needed to express all closed matrix model amplitudes.
This allows us to integrate the holomorphic anomaly equation up to holomorphic
modular terms that we fix by the gap condition up to genus four. There is an
one-dimensional submanifold of the moduli space in which the spectral curve
becomes the Seiberg--Witten curve and the ring reduces to the non-holomorphic
modular ring of the group . On that submanifold, the gap conditions
completely fix the holomorphic ambiguity and the model can be solved explicitly
to very high genus. We use these results to make precision tests of the
connection between the large order behavior of the 1/N expansion and
non-perturbative effects due to instantons. Finally, we argue that a full
understanding of the large genus asymptotics in the multi-cut case requires a
new class of non-perturbative sectors in the matrix model.Comment: 51 pages, 8 figure
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