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E. E. Donets

Publications and source records attributed to E. E. Donets.

At least 19 recordsLinked to original sources
arXiv2015

Algorithm for Solving the Optimization Problem for the Temperature Distribution on a Plate

The work describes the maximization problem regarding heating of an area on the surface of a thin plate within a given temperature range. The solution of the problem is applied to ion injectors. The given temperature range corresponds to a required pressure of a saturated gas comprising evaporated atoms of the plate material. In order to find the solution, a one-parameter optimization problem was formulated and implemented leading to optimization of the plate's specific geometry. It was shown that a heated area can be increased up to 23.5% in comparison with the regular rectangle form of a given plate configuration.

physics.comp-ph↗
arXiv2015

Electron string ion sources for carbon ion cancer therapy accelerators

The Electron String type of Ion Sources (ESIS) was developed, constructed and tested first in the Joint Institute for Nuclear Research. These ion sources can be the appropriate sources for production of pulsed C4+ and C6+ ion beams which can be used for cancer therapy accelerators. In fact the test ESIS Krion-6T already now at the solenoid magnetic field only 4.6 T provides more than 10^10 C4+ ions per pulse and about 5*10^9 C6+ ions per pulse. Such ion sources could be suitable for application at synchrotrons. It was also found, that Krion-6T can provide more than 10^11 C6+ ions per second at 100 Hz repetition rate, and the repetition rate can be increased at the same or larger ion output per second. This makes ESIS applicable at cyclotrons as well. As for production of 11C radioactive ion beams ESIS can be the most economic kind of ion source. To proof that the special cryogenic cell for pulse injection of gaseous species into electron string was successfully tested using the ESIS Krion-2M.

physics.acc-ph↗
arXiv2004

Unstable even-parity eigenmodes of the regular static SU(2) Yang-Mills-dilaton solutions

In this paper we obtain unstable even-parity eigenmodes to the static regular spherically symmetric solutions of the SU(2) Yang-Mills-dilaton coupled system of equations in 3+1 Minkowski space-time. The corresponding matrix Sturm-Liouville problem is solved numerically by means of the continuous analogue of Newton's method. The method, being the powerful tool for solving both boundary-value and Sturm-Liouville problems, is described in details.

gr-qc↗
arXiv2003

Self-similarity and singularity formation in a coupled system of Yang-Mills-dilaton evolution equations

We study both analytically and numerically a coupled system of spherically symmetric SU(2) Yang-Mills-dilaton equation in 3+1 Minkowski space-time. It has been found that the system admits a hidden scale invariance which becomes transparent if a special ansatz for the dilaton field is used. This choice corresponds to transition to a frame rotated in the $\ln r-t$ plane at a definite angle. We find an infinite countable family of self-similar solutions which can be parametrized by the $N$ - the number of zeros of the relevant Yang-Mills function. According to the performed linear perturbation analysis, the lowest solution with N=0 only occurred to be stable. The Cauchy problem has been solved numerically for a wide range of smooth finite energy initial data. It has been found that if the initial data exceed some threshold, the resulting solutions in a compact region shrinking to the origin, attain the lowest N=0 stable self-similar profile, which can pretend to be a global stable attractor in the Cauchy problem. The solutions live a finite time in a self-similar regime and then the unbounded growth of the second derivative of the YM function at the origin indicates a singularity formation, which is in agreement with the general expectations for the supercritical systems.

hep-th↗
arXiv2001

Nuclear astrophysics researches in an ion trap apparatus

At low energies, far below Coulumb barrier, fusion nuclear reactions are very sensitive to its shape, which is usually in experiments modified by atomic electrons of targer or both projectile and target particles. This article describes proposal on construction of an installation and measurements of excitation functions for d(d,p)t reaction in the region 1.5<E_{cm}<12.0 keV for 3^He(d,p)4^He reaction in the region 6.5<E_{cm}<15.0 keV center of mass energy in the conditions when the both beam and target particles would be in bare nuclear states. The technology of Electron Beam Ion Sources and Traps can provide such experimental conditions. Possibilities to study some other reactions are also considered.

astro-ph↗
arXiv2000

Brane Vacuum as Chain of Rotators

We analyse the noncommutative U(1) sigma model, which arises from the vacuum dynamics of the noncommutative charged tachyonic field. The sector of ``spherically symmetric'' excitations of the model is equivalent to a chain of rotators. Classical solutions for this model are found, which are static and ``spherically symmetric'' in noncommutative spatial dimensions. The limit of small noncommutativity reveals the presence of Polyakov vortices in the model. A generalisation of the model to q-deformed space, which may serve as a regularisation of the non-deformed model is also considered.

hep-th↗
arXiv2000

N=4 Superconformal Mechanics and the Potential Structure of AdS Spaces

The dynamics of an N=4 spinning particle in a curved background is described using the N=4 superfield formalism. The $SU(2)_{local}\times SU(2)_{global}$ N=4 superconformal symmetry of the particle action requires the background to be a real "Kähler-like" manifold whose metric is generated by a sigma-model superpotential. The anti-de-Sitter spaces are shown to belong to this class of manifolds.

hep-th↗
arXiv2000

Partial supersymmetry breaking in Multidimensional N=4 SUSY QM

The multidimensional N=4 supersymmetric quantum mechanics (SUSY QM) is constructed and the various possibilities for partial supersymmetry breaking are discussed. It is shown that quantum mechanical models with one quarter, one half and three quarters of unbroken(broken) supersymmetries can exist in the framework of the multidimensional N=4 SUSY QM.

hep-th↗
arXiv1999

N=4 Supersymmetric Multidimensional Quantum Mechanics, Partial SUSY Breaking and Superconformal Quantum Mechanics

The multidimensional N=4 supersymmetric quantum mechanics (SUSY QM) is constructed using the superfield approach. As a result, the component form of the classical and quantum Lagrangian and Hamiltonian is obtained. In the considered SUSY QM both classical and quantum N=4 algebras include central charges, and this opens various possibilities for partial supersymmetry breaking. It is shown that quantum mechanical models with one quarter, one half and three quarters of unbroken(broken) supersymmetries can exist in the framework of the multidimensional N=4 SUSY QM, while the one-dimensional N=4 SUSY QM, constructed earlier, admits only one half or total supersymmetry breakdown. We illustrate the constructed general formalism, as well as all possible cases of the partial SUSY breaking taking as an example a direct multidimensional generalization of the one-dimensional N=4 superconformal quantum mechanical model. Some open questions and possible applications of the constructed multidimensional N=4 SUSY QM to the known exactly integrable systems and problems of quantum cosmology are briefly discussed.

hep-th↗
arXiv1998

Towards N=2 $SUSY$ Homogeneous Quantum Cosmology; Einstein--Yang--Mills systems

The application of N=2 supersymmetric quantum mechanics for the quantization of homogeneous systems coupled with gravity is discussed. Starting with the superfield formulation of an N=2 SUSY sigma model, Hermitian self-adjoint expressions for quantum Hamiltonians and Lagrangians for any signature of a sigma-model metric are obtained. This approach is then applied to coupled SU(2) Einstein-Yang-Mills (EYM) systems in axially symmetric $Bianchi$-type I, II, VIII, IX, $Kantowski-Sachs$, and closed $Friedmann-Robertson-Walker$ cosmological models. It is shown that all these models admit the embedding into the N=2 SUSY sigma model with the explicit expressions for superpotentials being direct sums of gravitational and Yang-Mills (YM) parts. In addition, the YM parts of superpotentials exactly coincide with the corresponding Chern-Simons terms. The spontaneous SUSY breaking caused by YM instantons in EYM systems is discussed in a number of examples.

gr-qc↗
arXiv1998

Evolution of Nonlinear Perturbations Inside Einstein-Yang-Mills Black Holes

We present our results on numerical study of evolution of nonlinear perturbations inside spherically symmetric black holes in the SU(2) Einstein-Yang-Mills (EYM) theory. Recent developments demonstrate a new type of the behavior of the metric for EYM black hole interiors; the generic metric exhibits an infinitely oscillating approach to the singularity, which is a spacelike but not of the mixmaster type. The evolution of various types of spherically symmetric perturbations, propagating from the internal vicinity of the external horizon towards the singularity is investigated in a self-consistent way using an adaptive numerical algorithm. The obtained results give a strong numerical evidence in favor of nonlinear stability of the generic EYM black hole interiors. Alternatively, the EYM black hole interiors of S(chwarzschild)-type, which form only a zero measure subset in the space of all internal solutions are found to be unstable and transform to the generic type as perturbations are developed.

gr-qc↗
arXiv1997

Singularities Inside Hairy Black Holes

We show that the Strong Cosmic Censorship is supported by the behavior of generic solutions on the class of static spherically symmetric black holes in gravitating gauge models and their stringy generalizations.

gr-qc↗
arXiv1997

Internal structure of non-Abelian black holes and nature of singularity

Recent results concerning the internal structure of static spherically-symmetric non-Abelian black holes in the Einstein-Yang-Mills (EYM) theory and its generalizations including scalar fields are reviewed and discussed with an emphasis on the problem of a generic singularity in black holes. It is argued that in the theories admitting a violation of the naive no-hair conjecture the structure of singularity is essentially affected by the "hair roots". This invalidates an image of a non-Abelian black hole as a Schwarzschild black hole sitting inside the soliton. We give an analytic description of the generic oscillatory approach to the singularity in the pure EYM theory in terms of a divergent discrete sequence and show that the mass function is exponentially growing "in average". The second type of a generic approach to the singularity in hairy black holes is a "power-law mass inflation" which is realized in the theories including scalar fields. Both singularities are spacelike and no Cauchy horizons are met in the full interior region in conformity with the Strong Cosmic Censorship conjecture. Black holes violating this conjecture exist only for certain discrete values of the event horizon radius thus forming a subset of zero measure.

hep-th↗
arXiv1997

Power-law mass inflation in Einstein-Yang-Mills-Higgs black holes

Analytical formulas are presented describing a generic singularity inside the static spherically symmetric black holes in the SU(2) Einstein-Yang-Mills-Higgs theories with triplet or doublet Higgs field. The singularity is spacelike and exhibits a `power-low mass inflation'. Alternatively this asymptotic may be interpreted as a pointlike singularity with a non-vanishing shear in the Kantowski-Sachs anisotropic cosmology.

gr-qc↗
arXiv1997

Singularities inside non-Abelian black holes

Singularities inside static spherically symmetric black holes in the SU(2) Einstein-Yang-Mills and Einstein-Yang-Mills-dilaton theories are investigated. Analytical formulas are presented describing oscillatory and power law metric behavior near spacelike singularities in generic solutions.

gr-qc↗
arXiv1997

Internal Structure of Einstein-Yang-Mills Black Holes

It is shown that a generic black hole solution of the SU(2) Einstein-Yang-Mills equations develops a new type of an infinitely oscillating behavior near the singularity. Only for certain discrete values of the event horizon radius exceptional solutions exist, possessing an inner structure of the Schwarzschild or Reissner-Nordstrom type.

gr-qc↗
arXiv1993

Non-Abelian Cornucopions

An infinite family of cornucopions is found within the $SU(2)\times U(1)$ sector of the 4--d heterotic string low-energy theory, the extremal $U(1)$ magnetic dilatonic black hole being the lowest energy state. Non-abelian cornucopions are interpreted as sphalerons associated with potential barriers separating topologically distinct Yang-Mills vacua on the $U(1)$ cornucopion background. A mass formula for non-abelian dilatonic black holes is derived, and the free energy is calculated through the Euclidean action.

hep-th↗