arXiv subjects

O. Kovalenko

Publications and source records attributed to O. Kovalenko.

7 recordsLinked to original sources

arXiv2025

Some optimal recovery problems for operators on classes of $L$-space valued functions

We solve three optimal recovery problems for operators on classes of $L$-space (which is a semilinear metric space with two additional axioms that connect the metric with the algebraic operations) valued functions that are defined by a majorant of their modulus of continuity. Consideration of $L$-spaces valued functions allows to treat multi- and fuzzy-valued functions, as well as random processes and other non-real valued functions in a unified manner.

math.FA↗

arXiv2019

New Test of Modulated Electron Capture Decay of Hydrogen-Like $^{142}$Pm Ions: Precision Measurement of Purely Exponential Decay

An experiment addressing electron capture (EC) decay of hydrogen-like $^{142}$Pm$^{60+}$ ions has been conducted at the experimental storage ring (ESR) at GSI. The decay appears to be purely exponential and no modulations were observed. Decay times for about 9000 individual EC decays have been measured by applying the single-ion decay spectroscopy method. Both visually and automatically analysed data can be described by a single exponential decay with decay constants of 0.0126(7) s$^{-1}$ for automatic analysis and 0.0141(7) s$^{-1}$ for manual analysis. If a modulation superimposed on the exponential decay curve is assumed, the best fit gives a modulation amplitude of merely 0.019(15), which is compatible with zero and by 4.9 standard deviations smaller than in the original observation which had an amplitude of 0.23(4).

nucl-ex↗

arXiv2018

Impact-parameter analysis of the new TOTEM pp data at 13 TeV: black disk limit excess

We revisit a discussion on the impact-parameter dependence of proton-proton elastic scattering amplitude with improved uncertainty calculation. This analysis allows to reveal the asymptotic properties of hadron interactions. New data indicates that the impact-parameter elastic scattering amplitude is slightly above the black disk limit at 13~TeV c.m.s. energy of the LHC reaching a value of $\mathrm{Im}\,H(s,0) = 0.512\pm 0.001\ \text{(sys+stat)} \pm 0.004\ \text{(norm)}$ confirming that black disk limit is violated at current collision energy, however it was not exceeded at 7~TeV. The growth trend of the impact-parameter amplitude imaginary part, extrapolated from previous and new data, indicates that it is unlikely that the amplitude is close to saturation. New analysis is consistent with smooth energy evolution of the elastic scattering amplitude and supersedes the earlier conclusion on the black disk limit excess observed at 7~TeV.

hep-ph↗

arXiv2015

Ultrafast electron-phonon-magnon interactions at noble metal-ferromagnet interfaces

Ultrafast optical excitation of gold-cobalt bilayers triggers the nontrivial interplay between the electronic, acoustic, and magnetic degrees of freedom. Laser-heated electrons generated at the gold-air interface diffuse through the layer of gold and strongly overheat the lattice in cobalt resulting in the emission of ultrashort acoustic pulses and generation of exchange-coupled magnons. Time-resolved optical measurements allow for extracting the thermal boundary (Kapitza) resistances at metal/metal interfaces and the hot electron diffusion length in ferromagnetic materials. Both the experimental data and the analytical treatment of the two-temperature model reveal the role of the Kapitza resistance in transient lattice overheating.

cond-mat.mtrl-sci↗

arXiv2014

Impact analysis of TOTEM data at the LHC: black disk limit exceeded

We discuss the profile of the impact--parameter dependent elastic scattering amplitude. Extraction of impact-parameter dependence from the dataset with inclusion of the experimental data on elastic scattering at the LHC energies helps to reveal the asymptotics of hadron interactions. Analysis of the data clearly indicates that the impact-parameter elastic scattering amplitude exceed the black disk limit at the LHC energy 7TeV and the inelastic overlap function reaches its maximum value at $b>0$

hep-ph↗

arXiv2013

Can the "standard" unitarized Regge models describe the TOTEM data?

The standard Regge poles are considered as inputs for two unitarization methods: eikonal and U-matrix. It is shown that only models with three input pomerons and two input odderons can describe the high energy data on $pp$ and $\bar pp$ elastic scattering including the new data from Tevatron and LHC. However, it seems that the both considered models (eikonal and U-matrix) require a further modification (e.g., to explore nonlinear reggeon trajectories and/or nonexponential vertex functions) for a more satisfactory description of the data at 19.0 GeV$\leq \sqrt{s}\leq$ 7 TeV and 0.01 $\leq |t|\leq $14.2 GeV$^{2}$.

hep-ph↗

arXiv2012

Magnetization switching by ultrashort acoustic pulses

It is shown theoretically that a single a few picoseconds long acoustic pulse can reverse magnetization in a magneto-strictive material Terfenol-D. Following giant magneto-elastic changes of free energy density the magnetization vector is kicked out of a local in-plane energy mininum and decays into another minimum. For acoustic pulse duration significantly shorter than magnetization precession period $τ_{ac}$<<$T_{prec}$, the switching threshold is determined by the {\it acoustic pulse area}, i.e. pulse integral in time domain, similar to coherent phenomena in optics. Simulation results are summarized in a magneto-acoustic switching diagram and discussed in the context of all-optical magnetization switching by circularly polarized light pulses.

cond-mat.mtrl-sci↗