18,190 research outputs found
The Accession of Finland and Sweden to NATO: Geopolitical implications for Russia's position in the Baltic Sea region
The article examines Sweden's and Finland's motives for ending their long-time non-aligned policies and joining NATO after Russia had launched a special military operation in Ukraine in February 2022. The two countries’ decision is shown to be in the interest of the United States, which has always sought to fill the geopolitical vacuum reigning after the collapse of the opposing Soviet bloc and the Soviet Union itself. Finland and Sweden were the missing links for Washington and NATO in the Baltic region and Northern Europe as a whole. The study analyses the major consequences of these geopolitical changes for Russia in the Baltic region. These include the increasing disparity in armed forces with NATO, the substantial expansion of the border with the Alliance, the acquisition of new territorial and infrastructural capabilities by NATO to deploy reinforcements and military equipment from member countries to the region, the potential stationing of nuclear weapons on the territories of new member countries, the risk of blockading the Kaliningrad region, as well as the Gulf of Finland, and the Danish straits for Russian vessels. It is stressed that in the current circumstances, Russia needs to consider multiple scenarios in the Baltic region. On the one hand, it must safeguard its interests with minimal damage. On the other hand, it is crucial to steer clear of uncontrolled escalation of tensions with NATO, as it entails the risk of a military clash
The Tails of the Crossing Probability
The scaling of the tails of the probability of a system to percolate only in
the horizontal direction was investigated numerically for correlated
site-bond percolation model for .We have to demonstrate that the
tails of the crossing probability far from the critical point have shape
where is the correlation
length index, is the probability of a bond to be closed. At
criticality we observe crossover to another scaling . Here is a scaling index describing the
central part of the crossing probability.Comment: 20 pages, 7 figures, v3:one fitting procedure is changed, grammatical
change
Random Walk with a Boundary Line as a Free Massive Boson with a Defect Line
We show that the problem of Random Walk with boundary attractive potential
may be mapped onto the free massive bosonic Quantum Field Theory with a line of
defect. This mapping permits to recover the statistical properties of the
Random Walks by using boundary --matrix and Form Factor techniques.Comment: 17 pages, Latex, 3 figures include
Oscillations of high energy neutrinos in matter: Precise formalism and parametric resonance
We present a formalism for precise description of oscillation phenomena in
matter at high energies or high densities, V > \Delta m^2/2E, where V is the
matter-induced potential of neutrinos. The accuracy of the approximation is
determined by the quantity \sin^2 2\theta_m \Delta V/2\pi V, where \theta_m is
the mixing angle in matter and \Delta V is a typical change of the potential
over the oscillation length (l \sim 2\pi/V). We derive simple and physically
transparent formulas for the oscillation probabilities, which are valid for
arbitrary matter density profiles. They can be applied to oscillations of high
energy (E > 10 GeV) accelerator, atmospheric and cosmic neutrinos in the matter
of the Earth, substantially simplifying numerical calculations and providing an
insight into the physics of neutrino oscillations in matter. The effect of
parametric enhancement of the oscillations of high energy neutrinos is
considered. Future high statistics experiments can provide an unambiguous
evidence for this effect.Comment: LaTeX, 5 pages, 1 figure. Linestyles in the figure corrected to match
their description in the caption; improved discussion of the accuracy of the
results; references added. Results and conclusions unchange
Four-dimensional integration by parts with differential renormalization as a method of evaluation of Feynman diagrams
It is shown how strictly four-dimensional integration by parts combined with
differential renormalization and its infrared analogue can be applied for
calculation of Feynman diagrams.Comment: 6 pages, late
Rotationally Invariant Hamiltonians for Nuclear Spectra Based on Quantum Algebras
The rotational invariance under the usual physical angular momentum of the
SUq(2) Hamiltonian for the description of rotational nuclear spectra is
explicitly proved and a connection of this Hamiltonian to the formalisms of
Amal'sky and Harris is provided. In addition, a new Hamiltonian for rotational
spectra is introduced, based on the construction of irreducible tensor
operators (ITO) under SUq(2) and use of q-deformed tensor products and
q-deformed Clebsch-Gordan coefficients. The rotational invariance of this
SUq(2) ITO Hamiltonian under the usual physical angular momentum is explicitly
proved, a simple closed expression for its energy spectrum (the ``hyperbolic
tangent formula'') is introduced, and its connection to the Harris formalism is
established. Numerical tests in a series of Th isotopes are provided.Comment: 34 pages, LaTe
Separable Structure of Many-Body Ground-State Wave Function
We have investigated a general structure of the ground-state wave function
for the Schr\"odinger equation for identical interacting particles (bosons
or fermions) confined in a harmonic anisotropic trap in the limit of large .
It is shown that the ground-state wave function can be written in a separable
form. As an example of its applications, this form is used to obtain the
ground-state wave function describing collective dynamics for trapped
bosons interacting via contact forces.Comment: J. Phys. B: At. Mol. Opt. Phys. 33 (2000) (accepted for publication
- …