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Vojtech Kundrat

Publications and source records attributed to Vojtech Kundrat.

13 recordsLinked to original sources
arXiv2025

Anisotropic Phonon Dynamics and Directional Transport in Actinide van der Waals Semiconductor USe$_3$

Direction-dependent charge transport and optical responses are characteristic of van der Waals (vdW) materials with strong in-plane anisotropy. While transition-metal trichalcogenides (TMTCs) exemplify this behavior, heavier analogs remain largely unexplored. In this study we examine USe$_3$ as an anisotropic vdW material and a heavier analog of the well-studied TMTCs. We reveal strong in-plane anisotropy using polarization-resolved Raman spectroscopy, investigate strain-induced shifts of phonon modes, and quantify direction-dependent charge-carrier mobility through transport measurements on field-effect devices. First-principles calculations based on density-functional theory corroborate our findings, providing a theoretical basis for our experimental observations. Casting USe$_3$ as an actinide analog of a TMTC establishes a platform for exploring low-dimensional semiconductors that combine strong in-plane anisotropy with f-electron physics.

cond-mat.mtrl-sci↗
arXiv2019

Eikonal model analysis of elastic proton-proton collisions at 52.8 GeV and 8 TeV

Under the influence of standardly used description of Coulomb-hadronic interference proposed by West and Yennie the protons have been interpreted as transparent objects; elastic events have been interpreted as more central than inelastic ones. It will be shown that using eikonal model the protons may be interpreted in agreement with usual ontological conception; elastic processes being more peripheral than inelastic ones. The corresponding results (differing fundamentally from the suggested hitherto models) will be presented by analyzing the most ample elastic data set measured at the ISR energy of 52.8 GeV and the LHC energy of 8 TeV. Detailed analysis of measured differential cross section will be performed and possibility of peripheral behavior on the basis of eikonal model will be presented. The impact of recently established electromagnetic form factors on determination of quantities specifying hadron interaction determined from the fits of experimental elastic data will be analyzed. The influence of some other assumptions on proton characteristics derived from elastic hadronic amplitude determined on the basis of experimental data will be studied, too.

hep-th↗
arXiv2017

Eikonal model analysis of elastic proton-proton collisions at 52.8 GeV and 8 TeV

Under the influence of standardly used description of Coulomb-hadronic interference proposed by West and Yennie the protons have been interpreted as transparent objects; elastic events have been interpreted as more central than inelastic ones. It is known that using more general eikonal model the measured elastic data may be interpreted also very differently; elastic processes being more peripheral than inelastic ones. The most ample elastic data set measured at ISR energy of 52.8 GeV have been recently reanalyzed with the help of the eikonal model and new results obtained. The impact of recently established electromagnetic form factors on determination of quantities specifying hadron interaction determined from the fits of experimental elastic data have been studied. The influence of some other assumptions on proton characteristics derived from elastic hadronic scattering amplitude determined on the basis of experimental data have been analyzed, too. It concerns mainly the assumed $t$-dependence of phase of elastic hadronic amplitude. The results may be then compared to similar analysis of experimental data at much higher LHC energy of 8 TeV recently published by TOTEM experiment.

hep-ph↗
arXiv2016

Dependence of elastic hadron collisions on impact parameter

Elastic proton-proton collisions represent probably the greatest ensemble of available measured data, the analysis of which may provide large amount of new physical results concerning fundamental particles. It is, however, necessary to analyze first some conclusions concerning pp collisions and their interpretations differing fundamentally from our common macroscopic experience. It has been argued, e.g., that elastic hadron collisions have been more central than inelastic ones, even if any explanation of the existence of so different process, i.e., elastic and inelastic (with hundreds of secondary particles) collisions, under the same conditions has not been given until now. The given conclusion has been based on a greater number of simplifying mathematical assumptions (done already in earlier calculations), without their influence on physical interpretation being analyzed and entitled; the corresponding influence has started to be studied in the approach based on eikonal model. The possibility of peripheral interpretation of elastic collisions will be demonstrated and corresponding results summarized. The arguments will be given why no preference may be given to the mentioned centrality against the standard peripheral behaviour. The corresponding discussion of contemporary description of elastic hadronic collision in dependence on impact parameter will be summarized and the justification of some important assumptions will be considered.

hep-ph↗
arXiv2015

Elastic scattering of hadrons without optical theorem

All contemporary phenomenological models of elastic hadronic scattering have been based on the assumption of validity of optical theorem that was overtaken from optics. It has been stated that it may be proven in particle physics. However, it will be shown that its derivation in the framework of unitary S-matrix theory (which is supposed to be the most general approach in this case) has been based on several requirements that do not correspond to the actual collision characteristics of two particles. It will be shown that especially in the case of short-ranged interaction (for which the theorem is used most frequently) it cannot be applied to. The analysis of corresponding collision experiments is to be done under new basic physical assumptions. The actual progress in the description of hadronic collision processes may exist only if the distribution of different initial states will be specified on the basis of impact parameter values of colliding particles and the dependence of collision probability on this parameter will be established, without limiting corresponding conclusions by the assumption of optical theorem validity from the very beginning.

nucl-th↗
arXiv2014

Elastic hadron scattering and optical theorem

All contemporary phenomenological models of elastic hadronic scattering have been based in principle on the assumption of optical theorem validity that has been overtaken from optics. It will be shown that the given theorem which has not been actually proved in particle physics cannot be applied to short-ranged strong interactions. The analysis of corresponding collision experiments is to be done under new basic assumptions. The actual progress in description of hadronic collision processes might then exist only if the initial states are specified on the basis of impact parameter values of colliding particles and probability dependence on this parameter is established, without limiting corresponding conclusion by optical theorem validity.

nucl-th↗
arXiv2014

Two different physical interpretations of Schroedinger equation

The assumptions added by Bohr and concerning the Hilbert space (formed by all solutions of Schroedinger equation) changed fundamentally the original physical interpretation of these solutions proposed earlier by Schroedinger. This new alternative was refused by Einstein on the basis of the EPR Gedankenexperiment, but accepted fully for microscopic reality by scientific community. Both the quantum alternatives were discussed, however, again later. Bell tried to find a possibility how to decide between them; he generalized Einstein's Gedankenexperiment assuming that also spins of two detected particles would be measured. He derived then some inequality for a special combination of four coincidence probabilities, and it was commonly assumed that his inequality held for the original Schroedinger interpretation but not in Bohr's Copenhagen quantum mechanics; without any actual proof having been given. Corresponding experiments were proposed and finished in 1982. The violation of Bell's inequality was then interpreted as decisive victory of Bohr's theory. However, it will be shown that Bell's inequality has been interpreted mistakenly. It has been based always on some assumption that does not hold in any probabilistic theory (i.e., in the given spin experiment) but only in deterministic classical theory. There is not any argument for preferring the Copenhagen quantum mechanics and against Einstein's critical standpoint. Some other consequences will be mentioned, too.

quant-ph↗
arXiv2009

Theoretical aspects of high energy elastic nucleon scattering

The eikonal model must be denoted as strongly preferable for the analysis of elastic high-energy hadron collisions. The given approach allows to derive corresponding impact parameter profiles that characterize important physical features of nucleon collisions, e.g., the range of different forces. The contemporary phenomenological analysis of experimental data is, however, not able to determine these profiles unambiguously, i.e., it cannot give the answer whether the elastic hadron collisions are more central or more peripheral than the inelastic ones. However, in the collisions of mass objects (like protons) the peripheral behavior of elastic collisions should be preferred.

hep-ph↗
arXiv2009

Contemporary models of elastic nucleon scattering and their predictions for LHC

The analyses of elastic collisions of charged nucleons have been based standardly on West and Yennie formula. However, this approach has been shown recently to be inadequate from experimental as well as theoretical points of view. The eikonal model seems to be more pertinent as it enables to determine physical characteristics in impact parameter space. The contemporary phenomenological models cannot give, of course, any definite answer as the elastic collisions may be interpreted differently, as central or peripheral processes. Nevertheless, the predictions for the planned LHC energy have been given on their basis and the possibility of exact determination of luminosity has been considered.

hep-ph↗
arXiv2009

Optical theorem and elastic nucleon scattering

In the theoretical analysis of high-energy elastic nucleon scattering one starts commonly from the description based on the validity of optical theorem, which allows to derive the value of total cross section directly from the experimentally measured t-dependence of elastic differential cross section. It may be shown, however, that this theorem has been derived on the basis of one assumption that might be regarded perhaps as acceptable for long-range (e.g., Coulomb) forces but must be denoted as quite unacceptable for finite-range hadron forces. Consequently, the conclusions leading to the increase of total cross section with energy at higher collision energies must be newly analyzed. The necessity of new analysis concerns also the derivation of elastic scattering t-dependence at very low transverse momenta from measured data.

hep-ph↗
arXiv2007

To the theory of high-energy elastic nucleon collisions

The commonly used West and Yennie integral formula for the relative phase between the Coulomb and elastic hadronic amplitudes requires for the phase of the elastic hadronic amplitude to be constant at all kinematically allowed values of t. More general interference formula based on the eikonal model approach does not exhibit such limitation. The corresponding differences will be demonstrated and some predictions of different phenomenological models for elastic pp scattering at energy of 14 TeV at the LHC will be given. Special attention will be devoted to determination of luminosity from elastic scattering data; it will be shown that the systematic error might reach till 5 % if the luminosity is derived from the values in the center of the interference region with the help of West and Yennie formula.

hep-ph↗
arXiv2000

High-energy elastic hadron collisions and space structure of hadrons

The elastic and inelastic profiles have been derived from the measured elastic differential cross section data with the help of exact impact parameter representation of elastic scattering amplitude. The results obtained for $pp$ scattering at energy of 53 GeV and $\bar{p} p$ scattering at energy of 541 GeV have been presented. They indicate that nucleons can be regarded as objects characterized by a small core (diameter $\sim$ 0.4$÷$0.8 fm) and a half transparent outer shell (responsible mainly for elastic hadron scattering).

hep-ph↗