1,260 research outputs found
Proposal of an experimental scheme for realising a translucent eavesdropping on a quantum cryptographic channel
Purpose of this paper is to suggest a scheme, which can be realised with
today's technology and could be used for entangling a probe to a photon qubit
based on polarisation. Using this probe a translucent or a coherent
eavesdropping can be performed.Comment: in pres
Anomaly freedom in Seiberg-Witten noncommutative gauge theories
We show that noncommutative gauge theories with arbitrary compact gauge group
defined by means of the Seiberg-Witten map have the same one-loop anomalies as
their commutative counterparts. This is done in two steps. By explicitly
calculating the \epsilon^{\m_1\m_2\m_3\m_4} part of the renormalized
effective action, we first find the would-be one-loop anomaly of the theory to
all orders in the noncommutativity parameter \theta^{\m\n}. And secondly we
isolate in the would-be anomaly radiative corrections which are not BRS
trivial. This gives as the only true anomaly occurring in the theory the
standard Bardeen anomaly of commutative spacetime, which is set to zero by the
usual anomaly cancellation condition.Comment: LaTeX 2e, no macros, no figures, 32 A4 page
Insufficient treatment of severe depression in neuromyelitis optica spectrum disorder
OBJECTIVE: To investigate depression frequency, severity, current treatment, and interactions with somatic symptoms among patients with neuromyelitis optica spectrum disorder (NMOSD). METHODS: In this dual-center observational study, we included 71 patients diagnosed with NMOSD according to the International Panel for NMO Diagnosis 2015 criteria. The Beck Depression Inventory (BDI) was classified into severe, moderate, or minimal/no depressive state category. We used the Fatigue Severity Scale to evaluate fatigue. Scores from the Brief Pain Inventory and the PainDETECT Questionnaire were normalized to estimate neuropathic pain. Psychotropic, pain, and immunosuppressant medications were tabulated by established classes. RESULTS: Twenty-eight percent of patients with NMOSD (n = 20) had BDI scores indicative of moderate or severe depression; 48% of patients (n = 34) endorsed significant levels of neuropathic pain. Severity of depression was moderately associated with neuropathic pain (r = 0.341, p < 0.004) but this relationship was confounded by levels of fatigue. Furthermore, only 40% of patients with moderate or severe depressive symptoms received antidepressant medical treatment. Fifty percent of those treated reported persistent moderate to severe depressive symptoms under treatment. CONCLUSIONS: Moderate and severe depression in patients with NMOSD is associated with neuropathic pain and fatigue and is insufficiently treated. These results are consistent across 2 research centers and continents. Future research needs to address how depression can be effectively managed and treated in NMOSD
Quantum metamorphosis of conformal symmetry in N = 4 super Yang-Mills theory
In gauge theories, not all rigid symmetries of the classical action can be
maintained manifestly in the quantization procedure, even in the absence of
anomalies. If this occurs for an anomaly-free symmetry, the effective action is
invariant under a transformation that differs from its classical counterpart by
quantum corrections. As shown by Fradkin and Palchik years ago, such a
phenomenon occurs for conformal symmetry in quantum Yang-Mills theories with
vanishing beta function, such as the N = 4 super Yang-Mills theory. More
recently, Jevicki et al demonstrated that the quantum metamorphosis of
conformal symmetry sheds light on the nature of the AdS/CFT correspondence. In
this paper, we derive the conformal Ward identity for the bosonic sector of the
N = 4 super Yang-Mills theory using the background field method. We then
compute the leading quantum modification of the conformal transformation for a
specific Abelian background which is of interest in the context of the AdS/CFT
correspondence. In the case of scalar fields, our final result agrees with that
of Jevicki et al. The resulting vector and scalar transformations coincide with
those which are characteristic of a D3-brane embedded in AdS5 x S5.Comment: 20 pages, latex, no figures; comments and references added, the final
version to appear in NPB, the title changed on referee's reques
Transdiagnostic hippocampal damage patterns in neuroimmunological disorders
Hippocampal damage and associated cognitive deficits are frequently observed in neuroimmunological disorders, but comparative analyses to identify shared hippocampal damage patterns are missing. Here, we adopted a transdiagnostic analytical approach and investigated hippocampal shape deformations and associated cognitive deficits in four neuroimmunological diseases. We studied 120 patients (n = 30 in each group), including patients with multiple sclerosis (MS), neuromyelitis optica spectrum disorder (NMOSD), anti-NMDAR and anti-LGI1 encephalitis. A control group was matched to each patient sample from a pool of 79 healthy participants. We performed an MRI-based vertex-wise hippocampal shape analysis, extracted hippocampal volume estimates and scalar projection values as a measure of surface displacement. Cognitive testing included assessment of verbal memory and semantic fluency performance. Our cross-sectional analyses revealed characteristic patterns of bilateral inward deformations covering up to 32% of the hippocampal surface in MS, anti-NMDAR encephalitis, and anti-LGI1 encephalitis, whereas NMOSD patients showed no deformations compared to controls. Significant inversions were noted mainly on the hippocampal head, were accompanied by volume loss, and correlated with semantic fluency scores and verbal episodic memory in autoimmune encephalitis and MS. A deformation overlap analysis across disorders revealed a convergence zone on the left anterior hippocampus that corresponds to the CA1 subfield. This convergence zone indicates a shared downstream substrate of immune-mediated damage that appears to be particularly vulnerable to neuroinflammatory processes. Our transdiagnostic morphological view sheds light on mutual pathophysiologic pathways of cognitive deficits in neuroimmunological diseases and stimulates further research into the mechanisms of increased susceptibility of the hippocampus to autoimmunity
An algebraic approach to the Tavis-Cummings problem
An algebraic method is introduced for an analytical solution of the
eigenvalue problem of the Tavis-Cummings (TC) Hamiltonian, based on
polynomially deformed su(2), i.e. su_n(2), algebras. In this method the
eigenvalue problem is solved in terms of a specific perturbation theory,
developed here up to third order. Generalization to the N-atom case of the Rabi
frequency and dressed states is also provided. A remarkable enhancement of
spontaneous emission of N atoms in a resonator is found to result from
collective effects.Comment: 13 pages, 7 figure
A skeleton approximate solution of the Einstein field equations for multiple black-hole systems
An approximate analytical and non-linear solution of the Einstein field
equations is derived for a system of multiple non-rotating black holes. The
associated space-time has the same asymptotic structure as the Brill-Lindquist
initial data solution for multiple black holes. The system admits an
Arnowitt-Deser-Misner (ADM) Hamiltonian that can particularly evolve the
Brill-Lindquist solution over finite time intervals. The gravitational field of
this model may properly be referred to as a skeleton approximate solution of
the Einstein field equations. The approximation is based on a conformally flat
truncation, which excludes gravitational radiation, as well as a removal of
some additional gravitational field energy. After these two simplifications,
only source terms proportional to Dirac delta distributions remain in the
constraint equations. The skeleton Hamiltonian is exact in the test-body limit,
it leads to the Einsteinian dynamics up to the first post-Newtonian
approximation, and in the time-symmetric limit it gives the energy of the
Brill-Lindquist solution exactly. The skeleton model for binary systems may be
regarded as a kind of analytical counterpart to the numerical treatment of
orbiting Misner-Lindquist binary black holes proposed by Gourgoulhon,
Grandclement, and Bonazzola, even if they actually treat the corotating case.
Along circular orbits, the two-black-hole skeleton solution is quasi-stationary
and it fulfills the important property of equality of Komar and ADM masses.
Explicit calculations for the determination of the last stable circular orbit
of the binary system are performed up to the tenth post-Newtonian order within
the skeleton model.Comment: 15 pages, 1 figure, submitted to Phys. Rev. D, 3 references added,
minor correction
Investigation of stimulated dynamics in strongly anisotropic high-temperature superconductors system Bi-Pb-Sr-Ca-Cu-O
It is used the mechanical method of Abrikosov vortex stimulated dynamics
investigation in superconductors. With its help it was studied relaxation
phenomena in vortex matter of high-temperature superconductors. It established
that pulsed magnetic fields change the course of relaxation processes taking
place in vortex matter. The study of the influence of magnetic pulses differing
by their durations and amplitudes on vortex system of strongly anisotropic
high-temperature superconductors system Bi1.7Pb0.3Sr2Ca2Cu3O10-d showed the
presence of threshold phenomena. The small duration pulses do not change the
course of relaxation processes taking place in vortex matter. When the duration
of pulses exceeds some critical value (threshold), then their influence change
the course of relaxation process which is revealed by stepwise change of
relaxing mechanical moment.. These investigation showed that the time for
formatting of Abrikosov vortex lattice in Bi1.7Pb0.3Sr2Ca2Cu3O10-d is of the
order of 150 us which on the order of value exceeds the time necessary for
formation of a single vortex observed in isotropic high-temperature
superconductor HoBa2Cu3O7-d and on two orders exceeds the creation time of a
single vortex observed in classical type II superconductors.Comment: 6 pages, 0 figure
The repulsive nature of naked singularities from the point of view of Quantum Mechanics
We use the Dirac equation coupled to a background metric to examine what
happens to quantum mechanical observables like the probability density and the
radial current in the vicinity of a naked singularity of the
Reissner-Nordstr\"{o}m type. We find that the wave function of the Dirac
particle is regular in the point of the singularity. We show that the
probability density is exactly zero at the singularity reflecting
quantum-mechanically the repulsive nature of the naked singularity.
Furthermore, the surface integral of the radial current over a sphere in the
vicinity of the naked singularity turns out to be also zero.Comment: 11 page
Crucial Physical Dependencies of the Core-Collapse Supernova Mechanism
We explore with self-consistent 2D F{\sc{ornax}} simulations the dependence
of the outcome of collapse on many-body corrections to neutrino-nucleon cross
sections, the nucleon-nucleon bremsstrahlung rate, electron capture on heavy
nuclei, pre-collapse seed perturbations, and inelastic neutrino-electron and
neutrino-nucleon scattering. Importantly, proximity to criticality amplifies
the role of even small changes in the neutrino-matter couplings, and such
changes can together add to produce outsized effects. When close to the
critical condition the cumulative result of a few small effects (including
seeds) that individually have only modest consequence can convert an anemic
into a robust explosion, or even a dud into a blast. Such sensitivity is not
seen in one dimension and may explain the apparent heterogeneity in the
outcomes of detailed simulations performed internationally. A natural
conclusion is that the different groups collectively are closer to a realistic
understanding of the mechanism of core-collapse supernovae than might have
seemed apparent.Comment: 25 pages; 10 figure
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