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M. Yu. Kuchiev

Publications and source records attributed to M. Yu. Kuchiev.

At least 19 recordsLinked to original sources
arXiv2011

Radiative corrections in fermion bags bound by Higgs boson exchange

Radiative corrections for several heavy fermions bound together via the Higgs boson exchange are studied. The fermion bags considered include 12, or fewer, fermions occupying the lowest S_{1/2} shell. It is shown that for `moderately heavy' fermions with masses 0.4< m c^2< 1 TeV the radiative corrections are small, 10^{-2}, and have an attractive nature. Therefore they do not put existence of the fermion bag in doubt. This proves that these fermion bags can exist in nature.

hep-ph↗
arXiv2010

Amplitudes of radiative corrections in fermion bags bound by Higgs boson exchange

Properties of amplitudes that describe radiative corrections in a bag of heavy fermions bound by the Higgs boson exchange are studied. Classes of amplitudes, in which the large fermion mass is canceled out and hence produces no enhancement for the radiative corrections are found. For fermions with masses in the region 400< m < 1000 Gev all relevant amplitudes are found to possess this property. Correspondingly the radiative corrections for this range of masses are small. For very heavy fermions, m>1000 Gev, the processes described by diagrams with closed fermion loops are also mass-independent.

hep-ph↗
arXiv2008

Low-frequency plasma conductivity in the average-atom approximation

Low-frequency properties of a plasma are examined within the average-atom approximation, which presumes that scattering of a conducting electron on each atom takes place independently of other atoms. The relaxation time tau distinguishes a high-frequency region omega tau > 1, where the single-atom approximation is applicable explicitly, from extreme low frequencies omega tau < 1, where, naively, the single-atom approximation is invalid. A proposed generalization of the formalism, which takes into account many-atom collisions, is found to be accurate in all frequency regions, from omega =0 to omega tau >1, reproducing the Ziman formula in the static limit, results based on the Kubo-Greenwood formula for high frequencies, and satisfying the conductivity sum-rule precisely. The correspondence between physical processes leading to the conventional Ohm's law and the infrared properties of QED is discussed. The suggested average-atom approach to frequency-dependent conductivity is illustrated by numerical calculations for the an aluminum plasma in the temperature range 2--10 eV.

physics.plasm-ph↗
arXiv2007

Production of high energy particles in laser and Coulomb fields and e^+e^- antenna

A strong laser field and the Coulomb field of a nucleus can produce e^{+}e^{-} pairs. It is shown for the first time that there is a large probability that electrons and positrons created in this process collide after one or several oscillations of the laser field. These collisions can take place at high energy resulting in several phenomena. The quasielastic collision e^{+}e^{-} -> e^{+}e^{-} allows acceleration of leptons in the laser field to higher energies. The inelastic collisions allow production of high energy photons e^{+}e^{-}-> 2 gamma and muons, e^{+}e^{-} -> mu^{+}mu^{-}. The yield of high-energy photons and muons produced via this mechanism exceeds exponentially their production through conventional direct creation in laser and Coulomb fields. A relation of the phenomena considered with the antenna-mechanism of multiphoton absorption in atoms is discussed.

physics.atom-ph↗
arXiv2007

Electron-positron pair creation by Coulomb and laser fields in the tunneling regime

Electron-positron pair creation due to combined nuclear Coulomb and strong laser fields is investigated for the tunneling regime. The energy spectra and angular distributions of the pair are found analytically for the first time. The energy spectrum for each lepton exhibits a sharp maximum located well above the threshold for any polarization of the laser field. The angular distributions of leptons depend on the polarization: for the linear polarization both leptons move predominantly along the laser beam direction; for the circular polarization leptons are emitted in a thin-walled cone centered on the laser beam. The spectral and angular distributions found are governed by the intensity and frequency of the field, and the frequency independent total pair creation rates comply with the previously known results. A new method of calculation - the vicinal approximation - which uses the fact that the pair production takes place in the close vicinity of the nucleus, is suggested.

physics.atom-ph↗
arXiv2005

Coulomb problem for vector bosons

The Coulomb problem for vector bosons W incorporates a well known difficulty; the charge of the boson localized in a close vicinity of the attractive Coulomb center proves be infinite. This fact contradicts the renormalizability of the Standard Model, which presumes that at small distances all physical quantities are well defined. The paradox is shown to be resolved by the QED vacuum polarization, which brings in a strong effective repulsion that eradicates the infinite charge of the boson on the Coulomb center. This property allows to define the Coulomb problem for vector bosons properly, making it consistent with the Standard Model.

hep-th↗
arXiv2005

Coulomb problem for vector bosons versus Standard Model

The Coulomb problem for vector bosons W(+/-) propagating in an attractive Coulomb field incorporates a known difficulty, i.e. the total charge of the boson localized on the Coulomb center turns out infinite. This fact contradicts the renormalizability of the Standard model, which presumes that at small distances all physical quantities are well defined. The paradox is shown to be resolved by the QED vacuum polarization, which brings in a strong effective repulsion and eradicates the infinite charge of the boson on the Coulomb center. The effect makes the Coulomb problem for vector bosons well defined and consistent with the Standard Model.

hep-th↗
arXiv2005

Causality condition and reflection on event horizon

A new way to implement the causality condition on the event horizon of black holes is discovered. The metric of a black hole is shown to be a function of the complex-valued gravitational radius r_g => r_g + i0. The relation between this modification of the metric and the causality condition is established using the analyticity of the S-matrix, which describes scattering of probing particles on a back hole. The found property of the metric has strong manifestations in scattering and related phenomena. One of them is the unexpected effect of reflection of incoming particles on the event horizon, which strongly reduces the absorption cross section.

gr-qc↗
arXiv2004

Reflection on event horizon for collapsing black holes

It was argued recently that there exists an unexpected phenomenon, the reflection of incoming particles on the event horizon of black holes (Kuchiev(2003)). This means that a particle approaching the black hole can bounce back into the outside world due to those events that take part strictly on the horizon. Previously the effect was discussed in relation to eternal black holes. The present work shows that the effect exists for collapsing black holes as well.

gr-qc↗
arXiv2004

Reflection on event horizon and escape of particles from confinement inside black holes

Several recently found properties of the event horizon of black holes are discussed. One of them is the reflection of the incoming particles on the horizon. A particle approaching the black hole can bounce on the horizon back, into the outside world, which drastically reduces the absorption cross section in the infrared region. Another, though related phenomenon takes place for particles inside the horizon. A locked inside particle has, in fact, an opportunity to escape into the outside world. Thus, the confinement inside the horizon is not absolute. The escape from within the interior region of the horizon allows the transfer of information from this region into the outside world. This result may help resolve the information paradox for black holes. Both the reflection and escape phenomena happen due to pure quantum reasons, being impossible in the classical approximation.

gr-qc↗
arXiv2003

Exponential enhancement of nuclear reactions in condensed matter environment

A mechanism that uses the environment to enhance the probability of the nuclear reaction when a beam of accelerated nuclei collides with a target nucleus implanted in condensed matter is suggested. The effect considered is exponentially large for low collision energies. For t + p collision the mechanism becomes effective when the energy of the projectile tritium is below $\sim$ 1 Kev per nucleon. The gain in probability of the nuclear reaction is due to a redistribution of energy and momentum of the projectile in several ``preliminary'' elastic collisions with the target nucleus and the environmental nuclei in such a way that the final inelastic projectile-target collision takes place at a larger relative velocity, which is accompanied by a decrease of the center of mass energy. The gain of the relative velocity exponentially increases the penetration through the Coulomb barrier.

nucl-th↗
arXiv2003

Scattering of scalar particles by a black hole

The absorption cross section for scalar particle impact on a Schwarzschild black hole is found. The process is dominated by two physical phenomena. One of them is the well-known greybody factor that arises from the energy-dependent potential barrier outside the horizon that filters the incoming and outgoing waves. The other is related to the reflection of particles on the horizon (Kuchiev 2003). This latter effect strongly diminishes the cross section for low energies, forcing it to vanish in the infrared limit. It is argued that this is a general property, the absorption cross section vanishes in the infrared limit for scattering of particles of arbitrary spin.

gr-qc↗
arXiv2003

Reflection from black holes and space-time topology

The quantum corrections make the black hole capable of reflection: any particle that approaches the event horizon can bounce back in the outside world. The albedo of the black hole depends on its temperature. The reflection shares physical origins with the phenomenon of Hawking radiation; both effects are explained as consequences of the singular nature that the event horizon exhibits on the quantum level.

gr-qc↗
arXiv2003

Reflection, radiation and interference for black holes

Black holes are capable of reflection: there is a finite probability for any particle that approaches the event horizon to bounce back. The albedo of the black hole depends on its temperature and the energy of the incoming particle. The reflection shares its physical origins with the Hawking process of radiation, both of them arise as consequences of the mixing of the incoming and outgoing waves that takes place on the event horizon.

gr-qc↗
arXiv2003

Reflection from black holes

Black holes are presumed to have an ideal ability to absorb and keep matter. Whatever comes close to the event horizon, a boundary separating the inside region of a black hole from the outside world, inevitably goes in and remains inside forever. This work shows, however, that quantum corrections make possible a surprising process, reflection: a particle can bounce back from the event horizon. For low energy particles this process is efficient, black holes behave not as holes, but as mirrors, which changes our perception of their physical nature. Possible ways for observations of the reflection and its relation to the Hawking radiation process are outlined.

gr-qc↗
arXiv2003

Radiative corrections to parity-non-conservation in atoms

Recent progress in calculations of QED radiative corrections to parity nonconservation in atoms is reviewed. The QED vacuum polarization, the self-energy corrections and the vertex corrections are shown to be described very reliably by different methods used by different groups. All new calculations have recently converged to very close final values. Each separate radiative correction is very large, above 1 % for heavy atoms, but having different signs they partly compensate each other. Our results for the radiative corrections for all atoms are presented. The corrections are -0.54 % for 133 Cs, and -0.70% for 205 Tl, 208 Pb, and 209 Bi. The result for 133 Cs reconciles the most accurate atomic experimental data for the 6s-7s PNC amplitude in 133 Cs of Wood et al with the standard model.

hep-ph↗
arXiv2002

Z alpha expansion for self-energy radiative corrections to parity nonconservation in atoms

The self-energy and vertex QED radiative corrections to the parity nonconservation (PNC) amplitude in atoms are obtained using the perturbation theory in powers of (alpha Z). The calculated linear in (alpha Z) term gives -0.6 % for the PNC amplitude in Cs. The estimated nonlinear terms make corrections larger -0.9(2) %. This result brings the experimental data for the 6s-7s transition in 133 Cs in agreement with the standard model.

hep-ph↗