arXiv subjects

B. Vlahovic

Publications and source records attributed to B. Vlahovic.

At least 19 recordsLinked to original sources

arXiv2025

Examination of the lattice QCD-motivated strong attractive $\Omega N$ potentials in the $\Omega^- n p$ system

Within the framework of the Faddeev equations in configuration space, we examine the $\Omega^{-} np$ system, employing strongly attractive lattice HAL QCD and Yukawa-type meson exchange potentials for the $\Omega N$ interaction. Our formalism incorporates the attractive Coulomb force between the $\Omega^{-}$ and proton, treating the system as three non-identical particle pairs (the $ABC$ model). In this study, we assess the impact of the Coulomb interaction on the system and compare our results with recent $\Omega NN$ ($AAC$ model) calculations obtained using various approaches. The $ABC$ model yields low-energy characteristics for the $\Omega NN$ system that differ from previous calculations. The Coulomb potential has a marginal perturbative effect on the $AAC$ system, shifting the three-body binding energy by the Coulomb energy of the two-body $BC$ subsystem, but only slightly deviating the spatial configuration from isosceles triangle symmetry. These effects are primarily driven by the strong $\Omega N$ interaction. We demonstrate that the large binding energy of the $\Omega^{-} np$ system arises from the short-range behavior of the $\Omega N$ potentials.

nucl-th↗

arXiv2025

Study of light $\phi$-mesic nuclei with HAL QCD $\phi N$ interactions

We explore the possible existence of light $\phi$-mesic nuclei using HAL QCD $\phi N$ interactions for the $^2S_{1/2}$ and $^4S_{3/2}$ channels. Particularly, using the Faddeev formalism in configuration space, the $\phi NN$ system, and $^{9}_{\phi}$Be and $^{6}_{\phi\phi}$He nuclei within the framework of the three-body cluster model, are investigated. The $\phi\alpha$ effective potential, obtained through a folding procedure, involves the HAL QCD $\phi N$ interaction in the $^4S_{3/2}$ channel which does not lead to a bound state of the $\phi N$ pair while the $\phi N$ $^2S_{1/2}$ channel yields the bound state as the $^3_\phi$H nucleus. The $^4S_{3/2}$ potential ensures that the folding procedure is appropriate because there are no open channels like $\phi+N$ and $\phi +2N $ near or below the $\phi+ 4N$ threshold, and it utilizes different matter distributions of $^4$He proposed in the literature. The folding potential is approximated by the Woods-Saxon formula. The mirror systems $\phi$+$\alpha$+$\alpha$ and $\phi$+$\phi$+$\alpha$ have energy ranges from 1-11 MeV and 3-10~MeV, respectively. The predicted binding energies represent the minimal values for the hypothetical $\phi$ mesic nuclei $^{5}_{\phi}$He, $^{9}_{\phi}$Be and $^{6}_{\phi\phi}$He. The phenomenological $\alpha\alpha$ and $\phi\phi$ potentials are adopted from the literature.

nucl-th↗

arXiv2022

Supervised learning applied to high-dimensional millimeter wave transient absorption data for age prediction of perovskite thin-film

We have analyzed a limited sample set of 120 GHz, and 150 GHz time-resolved millimeter wave (mmW) photoconductive decay (mmPCD) signals of 300 nm thick air-stable encapsulated perovskite film (methyl-ammonium lead halide) excited using a pulsed 532-nm laser with fluence 10.6 micro-Joules per cm-2. We correlated 12 parameters derived directly from acquired mmPCD kinetic-trace data and its step-response, each with the sample-age based on the date of the experiment. Five parameters with a high negative correlation with sample age were finally selected as predictors in the Gaussian Process Regression (GPR) machine learning model for prediction of the age of the sample. The effects of aging (between 0 and 40,000 hours after film production) are quantified mainly in terms of a shift in peak voltage, the response ratio (conductance parameter), loss-compensated transmission coefficient, and the radiofrequency (RF) area of the transient itself (flux). Changes in the other step-response parameters and the decay length of the aging transients are also shown. The GPR model is found to work well for a forward prediction of the age of the sample using this method. It is noted that the Matern-5 over 2 GPR kernel for supervised learning provides the best realistic solution for age prediction with R squared around 0.97.

cond-mat.mtrl-sci↗

arXiv2021

Mass-Energy Equivalence in Bound Three-Nucleon Systems

The mass defect formula reflects the equivalence of mass and energy for bound nuclear systems. We study three-nucleon systems $^3$H and $^3$He, considering the neutron and proton as indistinguishable particles ($AAA$ model) or taking into account the real masses of neutrons and protons ($AAB$ model). We have focused on conceptual problems of the $AAA$ model, which is widely used for $3N$ calculations. In particular, the $AAA$ model is incompatible with the mass defect formula, which naturally corresponds to the $AAB$ model. In addition, the $AAA$ model has a cyclic permutation symmetry, which is breaking in the natural $AAB$ model. The latter problem cannot be eliminated within the perturbative $AAA$ approach, in which the mass difference effect is simulated by correcting the kinetic energy operator. Earlier it was reported that the accuracy of such $AAA$ calculations is 1~keV. An example of the $AAB$ calculation, we numerically estimate the effect of the difference between the neutron and proton masses on the energy calculated without any approximation with the accuracy of 0.1~keV. Another manifestation of the equivalence of mass $m$ and energy $E$ can be expressed by the formula $dE/dm=Const$. To show this dependence of the three-body energy on the nucleon mass, we performed realistic calculations within the $AAA$ approximation, varying the averaged nucleon mass. The mass-energy compensation effect for the three-body Hamiltonian is shown. According to this, we have determined the effective nucleon mass required to compensate for the perturbative effect of a three-body potential.

nucl-th↗

arXiv2021

3N potentials in the Faddeev coordinate space approach to Nd scattering

In the last decade, for studying 3$N$ bound states and $Nd$ scattering the Tucson-Melbourne (TM) and Urbana 3$N$ force derived from the chiral EFT have been applied. We plan to use the TM 3$N$ force for studying the $Nd$ scattering on the basis of the Faddeev equations in configuration space. In the given paper, we present our final formulas for components of the TM 3$N$ potential obtained in the coordinate space.

nucl-th↗

arXiv2020

Three-body model for $K(1460)$ resonance

The three-body $KK\bar K$ model for the $K(1460)$ resonance is developed on the basis of the Faddeev equations in configuration space. A single-channel approach is using with taking into account the difference of masses of neutral and charged kaons. It is demonstrated that a splitting the mass of the $K(1460)$ resonance takes a place around 1460 MeV according to $K^0K^0{\bar K}^0$, $K^0K^+K^-$ and $K^+K^0{\bar K}^0$, $ K^+K^+K^-$ neutral and charged particle configurations, respectively. The calculations are performed with two sets of $KK$ and $K\bar K$ phenomenological potentials, where the latter interaction is considered the same for the isospin singlet and triplet states. The effect of repulsion of the $KK$ interaction on the mass of the $KK\bar K$ system is studied and the effect of the mass polarization is evaluated. The first time the Coulomb interaction for description of the $K(1460)$ resonance is considered. The mass splitting in the $K$(1460) resonances is evaluated to be in range of 10 MeV with taking into account the Coulomb force. The three-body model with the $K\bar K$ potential, which has the different strength of the isospin singlet and triplet parts that are related by the condition of obtaining a quasi-bound three-body state is also considered. Our results are in reasonable agreement with the experimental mass of the $K(1460)$ resonance.

nucl-th↗

arXiv2020

A limit on the anisotropy of the one-way maximum attainable speed of the electron

We report here the first experimental result for the anisotropy of the one-way maximum attainable speed of the electron, $\vec{Δc_{1,e}}$, obtained via the study of a sidereal time dependence of a difference between the electron and positron beam momenta in the CESR storage ring at Cornell University. At 95 percent confidence, an upper limit for the component of $Δ\vec {c}_{1,e}/c$ perpendicular to Earth's rotational axis is found to be $5.5 \times 10^{-15}$.

hep-ex↗

arXiv2018

Isospin Effect in Three-Body Kaonic Clusters

The kaonic clusters $K^{-}K^{-}p$ and $ppK^{-}$ are described based on the configuration space Faddeev equations for $AAB$ system. The $AB$ interaction is given by isospin-dependent potentials. For this isospin model, we show that the relation $\left\vert E_{3}(V_{AA}=0)\right\vert~<~2\left\vert E_{2}\right\vert$ is satisfied when $E_{2}$ is the binding energy of the $AB$ subsystem and $E_{3}(V_{AA}=0)$ is the three-body binding energy when interaction between identical particles is omitted, $V_{AA}=0$. For the $NN{\bar K}$ system, taking into account weak attraction of $NN$ interaction the relation leads to the evaluation $|E_3|\le 2|E_2|$. The "isospinless model" for the kaonic clusters based on the isospin averaged $N{\bar K}$ potential demonstrates the opposite relation $\left\vert E_{3}(V_{AA}=0)\right\vert~>~2\left\vert E_{2}\right\vert$. The isospin "given charge formalism" is presented for $NN{\bar K}$ cluster. This formalism is related to isospin model by unitary transformation of the isospin basis. An interpretation of the "particle representation" for $NN{\bar K}$ system is proposed.

nucl-th↗

arXiv2017

On mass polarization effect in three-body systems

We evaluate the mass polarization term of the kinetic-energy operator for different three-body nuclear $AAB$ systems by employing the method of Faddeev equations in configuration space. For a three-boson system this term is determined by the difference of the doubled binding energy of the $AB$ subsystem $2E_{2}$ and the three-body binding energy $E_{3}(V_{AA}=0)$ when the interaction between the identical particles is omitted. In this case: $\left\vert E_{3}(V_{AA}=0)\right\vert >2\left\vert E_{2}\right\vert$. In the case of a system complicated by isospins(spins), such as the kaonic clusters $ K^{-}K^{-}p$ and $ppK^{-}$, the similar evaluation impossible. For these systems it is found that $\left\vert E_{3}(V_{AA}=0)\right\vert <2\left\vert E_{2}\right\vert$. A model with an $AB$ potential averaged over spin(isospin) variables transforms the later case to the first one. The mass polarization effect calculated within this model is essential for the kaonic clusters. Besides we have obtained the relation $|E_3|\le |2E_2|$ for the binding energy of the kaonic clusters.

nucl-th↗

arXiv2017

Spin-flip doublets of $^9$Be spectrum within a cluster model

The structure of the $^9$Be low-lying spectrum is studied within the cluster model $α+α+n$. In the model the total orbital momentum is fixed for each energy level. Thus each level is determined as a member of the spin-flip doublet corresponding to the total orbital momentum ($L^π=0^+, 2^+,4^+, 1^-, 2^-,3^-, 4^-$) of the system. The Ali-Bodmer potential (model E) is applied for the $αα$ interaction. We employ a local $αn$ potential which was constructed to reproduce the $α-n$ scattering data. The Pauli blocking is simulated by the repulsive core of the $s$-wave components of these potentials. Configuration space Faddeev equations are used to calculate the energy of the bound state ($E_{cal.}$=-1.493 MeV v.s. $E_{exp.}$=-1.5735 MeV) and resonances. A variant of the method of analytical continuation in the coupling constant is applied to calculate the energies of low-lying levels. Available $^9$Be spectral data are satisfactorily reproduced by the proposed model.

nucl-th↗

arXiv2015

Detecting somatic mutations in genomic sequences by means of Kolmogorov-Arnold analysis

The Kolmogorov-Arnold stochasticity parameter technique is applied for the first time to the study of cancer genome sequencing, to reveal mutations. Using data generated by next generation sequencing technologies, we have analyzed the exome sequences of brain tumor patients with matched tumor and normal blood. We show that mutations contained in sequencing data can be revealed using this technique thus providing a new methodology for determining subsequences of given length containing mutations i.e. its value differs from those of subsequences without mutations. A potential application for this technique involves simplifying the procedure of finding segments with mutations, speeding up genomic research, and accelerating its implementation in clinical diagnostic. Moreover, the prediction of a mutation associated to a family of frequent mutations in numerous types of cancers based purely on the value of the Kolmogorov function, indicates that this applied marker may recognize genomic sequences that are in extremely low abundance and can be used in revealing new types of mutations.

q-bio.GN↗

arXiv2015

Theory of Confined States of Positronium in Spherical and Circular Quantum Dots with Kane's Dispersion Law

Confined states of a positronium (Ps) in the spherical and circular quantum dots (QDs) are theoretically investigated in two size-quantization regimes: strong and weak. Two-band approximation of Kane dispersion law and parabolic dispersion law of charge carriers are considered. It is shown that the electronpositron pair instability is a consequence of dimensionality reduction, not of the size quantization (SQ). The binding energies for the Ps in circular and spherical QDs are calculated. The Ps formation dependence on the QD radius is studied.

cond-mat.mes-hall↗

arXiv2014

High-intensity positron microprobe at the Thomas Jefferson National Accelerator Facility

We present a conceptual design for a novel continuous wave electron-linac based high-intensity high-brightness slow-positron production source with a projected intensity on the order of 10$^{10}$ e$^+$/s. Reaching this intensity in our design relies on the transport of positrons (T$_+$ below 600 keV) from the electron-positron pair production converter target to a low-radiation and low-temperature area for moderation in a high-efficiency cryogenic rare gas moderator, solid Ne. This design progressed through Monte Carlo optimizations of: electron/positron beam energies and converter target thickness, transport of the e$^+$ beam from the converter to the moderator, extraction of the e$^+$ beam from the magnetic channel, a synchronized raster system, and moderator efficiency calculations. For the extraction of e$^+$ from the magnetic channel, a magnetic field terminator plug prototype has been built and experimental results on the effectiveness of the prototype are presented. The dissipation of the heat away from the converter target and radiation protection measures are also discussed.

physics.acc-ph↗

arXiv2014

Modeling of $^6_Λ$He hypernucleus within configuration space Faddeev approach

The cluster $^4\rm He+Λ+\rm n$ model is applied to describe the $^6_Λ$He hypernucleus. The consideration is based on the configuration space Faddeev equations for a system of non-identical particles. A set of the pair potentials includes the OBE simulating (NSC97f) model for the $Λ\rm n$ interaction and the phenomenological potentials for the $αΛ$ and $α\rm n$ interactions. We calculated energies of spin (1$^-$,2$^-$) doublet. For the 2$^-$ excitation energy, the obtained value is 0.18 MeV. The hyperon binding energy of the bound 1$^-$ state is less than the experimental value, which may be an evidence for violation of the exact three-body cluster structure.

nucl-th↗

arXiv2013

Dark Sectors and New, Light, Weakly-Coupled Particles

Dark sectors, consisting of new, light, weakly-coupled particles that do not interact with the known strong, weak, or electromagnetic forces, are a particularly compelling possibility for new physics. Nature may contain numerous dark sectors, each with their own beautiful structure, distinct particles, and forces. This review summarizes the physics motivation for dark sectors and the exciting opportunities for experimental exploration. It is the summary of the Intensity Frontier subgroup "New, Light, Weakly-coupled Particles" of the Community Summer Study 2013 (Snowmass). We discuss axions, which solve the strong CP problem and are an excellent dark matter candidate, and their generalization to axion-like particles. We also review dark photons and other dark-sector particles, including sub-GeV dark matter, which are theoretically natural, provide for dark matter candidates or new dark matter interactions, and could resolve outstanding puzzles in particle and astro-particle physics. In many cases, the exploration of dark sectors can proceed with existing facilities and comparatively modest experiments. A rich, diverse, and low-cost experimental program has been identified that has the potential for one or more game-changing discoveries. These physics opportunities should be vigorously pursued in the US and elsewhere.

hep-ph↗

arXiv2013

New Cosmological Model and Its Implications on Observational Data Interpretation

The paradigm of ΛCDM cosmology works impressively well and with the concept of inflation it explains the universe after the time of decoupling. However there are still a few concerns; after much effort there is no detection of dark matter and there are significant problems in the theoretical description of dark energy. We will consider a variant of the cosmological spherical shell model, within FRW formalism and will compare it with the standard ΛCDM model. We will show that our new topological model satisfies cosmological principles and is consistent with all observable data, but that it may require new interpretation for some data. Considered will be constraints imposed on the model, as for instance the range for the size and allowed thickness of the shell, by the supernovae luminosity distance and CMB data. In this model propagation of the light is confined along the shell, which has as a consequence that observed CMB originated from one point or a limited space region. It allows to interpret the uniformity of the CMB without inflation scenario. In addition this removes any constraints on the uniformity of the universe at the early stage and opens a possibility that the universe was not uniform and that creation of galaxies and large structures is due to the inhomogeneities that originated in the Big Bang.

physics.gen-ph↗

arXiv2012

Electron tunneling in chaotic InAs/GaAs quantum ring

Two dimensional InAs/GaAs quantum ring (QR) is considered using the effective potential approach. The symmetry of QR shape is violated as it is in the well-known Bohigas annular billiard. We calculate energy spectrum and studied the spatial localization of a single electron in such QR. For weak violation of the QR shape symmetry, the spectrum is presented as a set of quasi-doublets. Tunneling between quasi-doublet states is studied by the dependence on energy of the states. The dependence is changed with variation of the QR geometry that is related to the eccentricity of the QR. An interpretation of the experimental result obtained in [1] is proposed. We show that the "chaos-assisted tunneling" effect found in this paper can be explained by inter-band interactions occurred by anti-crossing of the levels with different "radial" quantum numbers.

cond-mat.mes-hall↗

arXiv2012

Quantum Mechanics of Semiconductor Quantum Dots and Rings

We consider the several phenomena which are taking place in Quantum Dots (QD) and Quantum Rings (QR): The connection of the Quantum Chaos (QC) with the reflection symmetry of the QD, Disappearance of the QC in the tunnel coupled chaotic QD, electron localization and transition between Double Concentric QR in the transverse magnetic field, transition of electron from QR to the QD located in the center of QR. Basis of this consideration is the effective Schrödinger equation for the corresponding systems.

cond-mat.mes-hall↗