216 research outputs found
Reparametrization-Invariant Path Integral in GR and "Big Bang" of Quantum Universe
The reparametrization-invariant generating functional for the unitary and
causal perturbation theory in general relativity in a finite space-time is
obtained. The region of validity of the Faddeev-Popov-DeWitt functional is
studied. It is shown that the invariant content of general relativity as a
constrained system can be covered by two "equivalent" unconstrained systems:
the "dynamic" (with "dynamic" evolution parameter as the metric scale factor)
and "geometric" (given by the Levi-Civita type canonical transformation to the
action-angle variables where the energy constraint converts into a new
momentum). "Big Bang", the Hubble evolution, and creation of matter fields by
the "geometric" vacuum are described by the inverted Levi-Civita (LC)
transformation of the geomeric system into the dynamic one. The particular case
of the LC transformations are the Bogoliubov ones of the particle variables
(diagonalizing the dynamic Hamiltonian) to the quasiparticles (diagonalizing
the equations of motion). The choice of initial conditions for the "Big Bang"
in the form of the Bogoliubov (squeezed) vacuum reproduces all stages of the
evolution of the Friedmann-Robertson-Walker Universe in their conformal
(Hoyle-Narlikar) versions.Comment: 21 pages, latex, 4 figures in postscrip
Magnetic Strings in Dilaton Gravity
First, I present two new classes of magnetic rotating solutions in
four-dimensional Einstein-Maxwell-dilaton gravity with Liouville-type
potential. The first class of solutions yields a 4-dimensional spacetime with a
longitudinal magnetic field generated by a static or spinning magnetic string.
I find that these solutions have no curvature singularity and no horizons, but
have a conic geometry. In these spacetimes, when the rotation parameter does
not vanish, there exists an electric field, and therefore the spinning string
has a net electric charge which is proportional to the rotation parameter. The
second class of solutions yields a spacetime with an angular magnetic field.
These solutions have no curvature singularity, no horizon, and no conical
singularity. The net electric charge of the strings in these spacetimes is
proportional to their velocities. Second, I obtain the ()-dimensional
rotating solutions in Einstein-dilaton gravity with Liouville-type potential. I
argue that these solutions can present horizonless spacetimes with conic
singularity, if one chooses the parameters of the solutions suitable. I also
use the counterterm method and compute the conserved quantities of these
spacetimes.Comment: 16 pages, no figure, references added, some minor correction
Experimental test for extra dimensions in Kaluza-Klein gravity
5D Kaluza-Klein gravity has several nonasymptotically flat solutions which
generally, possessed both electric and magnetic charges. In this paper we
suggest that these solutions can act as quantum virtual handles (wormholes) in
spacetime foam models. By applying a sufficently large, external electric
and/or magnetic field it may be possible to ``inflate'' these solutions from a
quantum to a classical state. This effect would lead to a possible experimental
signal for higher dimensions in multidimensional gravity.Comment: 11 pages, 3 PS.figures, REVTEX, the quality of the figures are
improve
Topological classification of black Hole: Generic Maxwell set and crease set of horizon
The crease set of an event horizon or a Cauchy horizon is an important object
which determines qualitative properties of the horizon. In particular, it
determines the possible topologies of the spatial sections of the horizon. By
Fermat's principle in geometric optics, we relate the crease set and the
Maxwell set of a smooth function in the context of singularity theory. We
thereby give a classification of generic topological structure of the Maxwell
sets and the generic topologies of the spatial section of the horizon.Comment: 22 pages, 6 figure
Accelerated Levi-Civita-Bertotti-Robinson Metric in D-Dimensions
A conformally flat accelerated charge metric is found in an arbitrary
dimension . It is a solution of the Einstein-Maxwell-null fluid with a
cosmological constant in dimensions. When the acceleration is zero
our solution reduces to the Levi-Civita-Bertotti-Robinson metric. We show that
the charge loses its energy, for all dimensions, due to the acceleration.Comment: Latex File, 12 page
On the electrodynamics of moving bodies at low velocities
We discuss the seminal article in which Le Bellac and Levy-Leblond have
identified two Galilean limits of electromagnetism, and its modern
implications. We use their results to point out some confusion in the
literature and in the teaching of special relativity and electromagnetism. For
instance, it is not widely recognized that there exist two well defined
non-relativistic limits, so that researchers and teachers are likely to utilize
an incoherent mixture of both. Recent works have shed a new light on the choice
of gauge conditions in classical electromagnetism. We retrieve Le
Bellac-Levy-Leblond's results by examining orders of magnitudes, and then with
a Lorentz-like manifestly covariant approach to Galilean covariance based on a
5-dimensional Minkowski manifold. We emphasize the Riemann-Lorenz approach
based on the vector and scalar potentials as opposed to the Heaviside-Hertz
formulation in terms of electromagnetic fields. We discuss various applications
and experiments, such as in magnetohydrodynamics and electrohydrodynamics,
quantum mechanics, superconductivity, continuous media, etc. Much of the
current technology where waves are not taken into account, is actually based on
Galilean electromagnetism
Anisotropic inharmonic Higgs oscillator and related (MICZ-)Kepler-like systems
We propose the integrable (pseudo)spherical generalization of the
four-dimensional anisotropic oscillator with additional nonlinear potential.
Performing its Kustaanheimo-Stiefel transformation we then obtain the
pseudospherical generalization of the MICZ-Kepler system with linear and
potential terms. We also present the generalization of the
parabolic coordinates, in which this system admits the separation of variables.
Finally, we get the spherical analog of the presented MICZ-Kepler-like system.Comment: 7 page
COVID-19 vaccine mRNABNT162b2 elicits human antibody response in milk of breastfeeding women
Objective: The objective of this research is to demonstrate the release of SARS-CoV-2 Spike (S) antibodies in human milk samples obtained by patients who have been vaccinated with mRNABNT162b2 vaccine. Methods: Milk and serum samples were collected in 10 volunteers 20 days after the first dose and 7 seven days after the second dose of the mRNABNT162b2 vaccine. Anti-SARS-CoV-2 S antibodies were measured by the Elecsys® Anti-SARS-CoV-2 S ECLIA assay (Roche Diagnostics AG, Rotkreuz, Switzerland), a quantitative electrochemiluminescence immunometric method. Results: At first sample, anti-SARS-CoV-2 S antibodies were detected in all serum samples (103.9 ± 54.9 U/mL) and only in two (40%) milk samples with a low concentration (1.2 ± 0.3 U/mL). At the second sample, collected 7 days after the second dose, anti-SARS-CoV-2 S antibodies were detected in all serum samples (3875.7 ± 3504.6 UI/mL) and in all milk samples (41.5 ± 47.5 UI/mL). No correlation was found between the level of serum and milk antibodies; the milk antibodies/serum antibodies ratio was on average 2% (range: 0.2–8.4%). Conclusion: We demonstrated a release of anti-SARS-CoV-2 S antibodies in the breast milk of women vaccinated with mRNABNT162b2. Vaccinating breastfeeding women could be a strategy to protect their infants from COVID-19 infection
Systems of Hess-Appel'rot Type and Zhukovskii Property
We start with a review of a class of systems with invariant relations, so
called {\it systems of Hess--Appel'rot type} that generalizes the classical
Hess--Appel'rot rigid body case. The systems of Hess-Appel'rot type carry an
interesting combination of both integrable and non-integrable properties.
Further, following integrable line, we study partial reductions and systems
having what we call the {\it Zhukovskii property}: these are Hamiltonian
systems with invariant relations, such that partially reduced systems are
completely integrable. We prove that the Zhukovskii property is a quite general
characteristic of systems of Hess-Appel'rote type. The partial reduction
neglects the most interesting and challenging part of the dynamics of the
systems of Hess-Appel'rot type - the non-integrable part, some analysis of
which may be seen as a reconstruction problem. We show that an integrable
system, the magnetic pendulum on the oriented Grassmannian has
natural interpretation within Zhukovskii property and it is equivalent to a
partial reduction of certain system of Hess-Appel'rot type. We perform a
classical and an algebro-geometric integration of the system, as an example of
an isoholomorphic system. The paper presents a lot of examples of systems of
Hess-Appel'rot type, giving an additional argument in favor of further study of
this class of systems.Comment: 42 page
The Maupertuis principle and canonical transformations of the extended phase space
We discuss some special classes of canonical transformations of the extended
phase space, which relate integrable systems with a common Lagrangian
submanifold. Various parametric forms of trajectories are associated with
different integrals of motion, Lax equations, separated variables and
action-angles variables. In this review we will discuss namely these induced
transformations instead of the various parametric form of the geometric
objects
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