201 research outputs found
Primordial pairing and binding of superheavy charge particles in the early Universe
Primordial superheavy particles, considered as the source of Ultra High
Energy Cosmic Rays (UHECR) and produced in local processes in the early
Universe, should bear some strictly or approximately conserved charge to be
sufficiently stable to survive to the present time. Charge conservation makes
them to be produced in pairs, and the estimated separation of particle and
antiparticle in such pair is shown to be in some cases much smaller than the
average separation determined by the averaged number density of considered
particles. If the new U(1) charge is the source of a long range field similar
to electromagnetic field, the particle and antiparticle, possessing that
charge, can form primordial bound system with annihilation timescale, which can
satisfy the conditions, assumed for this type of UHECR sources. These
conditions severely constrain the possible properties of considered particles.Comment: Latex, 4 pages. The final version to appear in Pis'ma ZhETF (the
conditions for the primordial binding are specified, some refs added
Vortex structure in exponentially shaped Josephson junctions
We report the numerical calculations of the static vortex structure and
critical curves in exponentially shaped long Josephson junctions for in-line
and overlap geometries. Each solution of the corresponding boundary value
problem is associated with the Sturm-Liouville problem whose minimal eigenvalue
allows to make a conclusion about the stability of the vortex. The change in
width of the junction leads to the renormalization of the magnetic flux in
comparison to the case of a linear one-dimensional model. We study the
influence of the model's parameters and, particularly, the shape parameter on
the stability of the states of the magnetic flux. We compare the vortex
structure and critical curves for the in-line and overlap geometries. Our
numerically constructed critical curve of the Josephson junction matches well
with the experimental one.Comment: 8 pages, 10 figures, NATO Advanced Research Workshop on "Vortex
dynamics in superconductors and other complex systems" Yalta, Crimea,
Ukraine, 13-17 September 200
A Cosmological Model with Dark Spinor Source
In this paper, we discuss the system of Friedman-Robertson-Walker metric
coupling with massive nonlinear dark spinors in detail, where the thermodynamic
movement of spinors is also taken into account. The results show that, the
nonlinear potential of the spinor field can provide a tiny negative pressure,
which resists the Universe to become singular. The solution is oscillating in
time and closed in space, which approximately takes the following form
g_{\mu\nu}=\bar R^2(1-\delta\cos t)^2\diag(1,-1,-\sin^2r ,-\sin^2r
\sin^2\theta), with light year, and
. The present time is about .Comment: 13 pages, no figure, to appear in IJMP
Big Bang Nucleosynthesis Constraints on Hadronically and Electromagnetically Decaying Relic Neutral Particles
Big Bang nucleosynthesis in the presence of decaying relic neutral particles
is examined in detail. All non-thermal processes important for the
determination of light-element abundance yields of 2H, 3H, 3He, 4He, 6Li, and
7Li are coupled to the thermonuclear fusion reactions to obtain comparatively
accurate results. Predicted light-element yields are compared to
observationally inferred limits on primordial light-element abundances to infer
constraints on the abundances and properties of relic decaying particles with
decay times in the interval 0.01 sec < tau < 10^(12) sec. Decaying particles
are typically constrained at early times by 4He or 2H, at intermediate times by
6Li, and at large times by the 3He/2H ratio. Constraints are shown for a large
number of hadronic branching ratios and decaying particle masses and may be
applied to constrain the evolution of the early Universe.Comment: 24 pages (revtex), 11 figures, title changed, matches published
versio
Skew-self-adjoint discrete and continuous Dirac type systems: inverse problems and Borg-Marchenko theorems
New formulas on the inverse problem for the continuous skew-self-adjoint
Dirac type system are obtained. For the discrete skew-self-adjoint Dirac type
system the solution of a general type inverse spectral problem is also derived
in terms of the Weyl functions. The description of the Weyl functions on the
interval is given. Borg-Marchenko type uniqueness theorems are derived for both
discrete and continuous non-self-adjoint systems too
Modern approaches to pharmacotherapy of chronic gastritis
The definition of gastritis is based on the histological features of the gastric mucosa. This is not the erythema observed during gastroscopy, and there are no specific clinical manifestations or symptoms that determine it. The modern classification of gastritis is based on time (acute and chronic), histological features, anatomical distribution and the main pathological mechanisms. Acute gastritis will develop into chronic if left untreated. Helicobacter pylori (H. pylori) is the most common cause of gastritis worldwide. However, from 60 to 70% H. pylori-negative subjects with functional dyspepsia or non-erosive gastroesophageal reflux were also found to have gastritis. H. pylori-negative gastritis is considered when a person meets all four of these criteria: negative triple staining of biopsies of the gastric mucosa, no history of treatment of H. pylori. In these patients, the cause of gastritis may be associated with tobacco smoking, alcohol consumption and / or the use of nonsteroidal anti-inflammatory drugs (NSAIDs) or steroids. Other causes of gastritis include autoimmune gastritis associated with antibodies of serum anti-parietal and anti-internal factor; organisms other than H. pylori, such as Mycobacterium avium intracellulare, Herpes simplex and Cytomegalovirus; gastritis caused by acid reflux; Rare causes of gastritis include collagen gastritis, sarcoidosis, eosinophilic gastritis and lymphocytic gastritis. The clinical picture, laboratory studies, gastroscopy, as well as histological and microbiological examination of tissue biopsies are important for the diagnosis of gastritis and its causes. Treatment of gastritis caused by H. pylori leads to the rapid disappearance of polymorphic-nuclear infiltration and a decrease in chronic inflammatory infiltrate with gradual normalization of the mucous membrane. Other types of gastritis should be treated based on their etiology
Five types of blow-up in a semilinear fourth-order reaction-diffusion equation: an analytic-numerical approach
Five types of blow-up patterns that can occur for the 4th-order semilinear
parabolic equation of reaction-diffusion type
u_t= -\Delta^2 u + |u|^{p-1} u \quad {in} \quad \ren \times (0,T), p>1,
\quad \lim_{t \to T^-}\sup_{x \in \ren} |u(x,t)|= +\iy, are discussed. For
the semilinear heat equation , various blow-up patterns
were under scrutiny since 1980s, while the case of higher-order diffusion was
studied much less, regardless a wide range of its application.Comment: 41 pages, 27 figure
Constraints on Supersymmetric Models from Catalytic Primordial Nucleosynthesis of Beryllium
The catalysis of nuclear reactions by negatively charged relics leads to
increased outputs of primordial ^6Li and ^9Be. In combination with
observational constraints on the primordial fractions of ^6Li and ^9Be, this
imposes strong restrictions on the primordial abundance and the lifetime of
charged relics. We analyze the constraints from the catalysis of ^9Be on
supersymmetric models in which the gravitino is the lightest supersymmetric
particle and a charged slepton--such as the lighter stau--the next-to-lightest
supersymmetric particle (NLSP). Barring the special cases in which the
primordial fraction of the slepton NLSP is significantly depleted, we find that
the ^9Be data require a slepton NLSP lifetime of less than 6x10^3 seconds. We
also address the issue of the catalytic destruction of ^6Li and ^9Be by late
forming bound states of protons with negatively charged relics finding that it
does not lead to any significant modification of the limit on the slepton
lifetime.Comment: 31 pages, 8 figures; minor additions, matches published versio
The Evolution of Compact Binary Star Systems
We review the formation and evolution of compact binary stars consisting of
white dwarfs (WDs), neutron stars (NSs), and black holes (BHs). Binary NSs and
BHs are thought to be the primary astrophysical sources of gravitational waves
(GWs) within the frequency band of ground-based detectors, while compact
binaries of WDs are important sources of GWs at lower frequencies to be covered
by space interferometers (LISA). Major uncertainties in the current
understanding of properties of NSs and BHs most relevant to the GW studies are
discussed, including the treatment of the natal kicks which compact stellar
remnants acquire during the core collapse of massive stars and the common
envelope phase of binary evolution. We discuss the coalescence rates of binary
NSs and BHs and prospects for their detections, the formation and evolution of
binary WDs and their observational manifestations. Special attention is given
to AM CVn-stars -- compact binaries in which the Roche lobe is filled by
another WD or a low-mass partially degenerate helium-star, as these stars are
thought to be the best LISA verification binary GW sources.Comment: 105 pages, 18 figure
Challenges and Lessons Learned from fabrication, testing and analysis of eight MQXFA Low Beta Quadrupole magnets for HL-LHC
By the end of October 2022, the US HL-LHC Accelerator Upgrade Project (AUP)
had completed fabrication of ten MQXFA magnets and tested eight of them. The
MQXFA magnets are the low beta quadrupole magnets to be used in the Q1 and Q3
Inner Triplet elements of the High Luminosity LHC. This AUP effort is shared by
BNL, Fermilab, and LBNL, with strand verification tests at NHMFL. An important
step of the AUP QA plan is the testing of MQXFA magnets in a vertical cryostat
at BNL. The acceptance criteria that could be tested at BNL were all met by the
first four production magnets (MQXFA03-MQXFA06). Subsequently, two magnets
(MQXFA07 and MQXFA08) did not meet some criteria and were disassembled. Lessons
learned during the disassembly of MQXFA07 caused a revision to the assembly
specifications that were used for MQXFA10 and subsequent magnets. In this
paper, we present a summary of: 1) the fabrication and test data of all the
MQXFA magnets; 2) the analysis of MQXFA07/A08 test results with
characterization of the limiting mechanism; 3) the outcome of the
investigation, including the lessons learned during MQXFA07 disassembly; and 4)
the finite element analysis correlating observations with test performance
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