Search

Positronium spectrum and lifetimes are known with a high precision. The situation is different for positronium moving across a magnetic field. The total momentum does not commute with the Hamiltonian and is replaced by conserved pseudomomentum. The internal dynamics is not separated from the motion of the system as a whole. The Coulomb potential well is distorted and a wide outer potential well is created. We analytically determine the energy spectrum for a broad range of the magnetic field and pseudomomentum values. We locate the region of these parameters for which the ground state resides in the outer well. The results may play a role in the suppression of pulsars radio emission (polar cap problem).

Increasingly precise astrophysical observations of the last decade in combination with intense theoretical studies allow for drawing a conclusion about potential Quark Matter presence in Neutron Stars interiors. Quark Matter may form the Neutron Star inner core or be immersed in the form of bubbles, or droplets. We consider the second scenario and demonstrate that even a small fraction of quark matter bubbles can lead to a high nonlinearity of the sound wave. Below the bubble resonant frequency the sound speed is lower than the ambient value. At the resonance it sharply grows. The peak is constrained by viscous dissipation. Above the resonance the speed exceeds the pure neutron star matter value. The dispersion equation for the bubbly neutron star compressibility is derived., Comment: v4: 23 pages, 3 figures; the content revised, new sections are added, some statements and typos corrected, the main statements unchanged

The possibility of neutron swapping between the ordinary and mirror sectors is today a subject of a great many theoretical and experimental studies. In this paper, we investigate the neutron-mirror neutron transitions in different environments from vacuum to neutron star. Our approach is based on the density matrix formalism, Lindblad and Bloch equations and the implication of the seesaw mechanism to the Hamiltonian diagonalization., Comment: v5: 17 pages, 0 figures; equations (17)-(19) and several typos corrected

We compute the soft real photon emission rate from the QCD matter in the vicinity of the critical line at moderate density and the temperature approaching the critical one from above. The obtained production rate exhibits a steep rise close to $T_c$ due to the formation of the slow fluctuation mode., Comment: 20 pages, 3 figures; v4: error on p.2 corrected, comments to Eq.(21) added

The transition of QGP from fluid-dynamical regime to freeze-out is accompanied by the onset of instabilities. In the present paper we investigate the impact of the magnetic field on the Rayleigh instability. We show that extremely strong field generated in peripheral heavy ion collisions has an insignificant influence on the Rayleigh bubble dynamics. Magnetic "friction" turns out to be much weaker than the viscous one., Comment: 12 pages, no figures: a completely revised v2 -- the title and the abstract are replaced, new equations with explanations are added, several insertions are made, the list of references is correspondingly enlarged

We show that at finite density pressure-pressure and current-current correlators exhibit divergences at $T_c$ owing to the fluctuations of the diquark field. Specifically, this leads to a significant excess of the soft photon production rate near $T_c$., Comment: 3 pages, 1 figure; contribution to the 2019 QCD session of the 54th Rencontres de Moriond

We examine the behavior of sound attenuation and bulk viscosity near the 2'nd order QCD phase transition at finite density. A dynamical model is presented describing the coupled evolution of sound mode and a slow mode of fluctuations., Comment: 4 pages, 1 figure, contribution to the proceedings of the Rencontres de Moriond 2018 on QCD and High Energy Interactions

The mass and the wave function of doubly charmed $\Xi^{++}_{cc}$ (ccu) baryon are evaluated using Green Function Monte Carlo method to solve the three-body problem with Cornell potential. The mass of $\Xi^{++}_{cc}$ with spin $1/2$ is in a good agreement with the LHCb value. Simulation of the wave function by random walks resulted in a configuration of the quark-diquark type. The radius of $\Xi^{++}_{cc}$ is much larger than the size needed for a large isospin splitting. The prediction for the $\Omega_{cc}$ mass is presented., Comment: 5 pages, no figures; v4: the title, the abstract and the introduction are replaced, list of references enlarged, misprints corrected

We propose a new approach based on the Lindblad and Bloch equations for the density matrix to the problem of a neutron into an antineutron conversion. We consider three strategies to search for conversion: experiments with trapped neutrons, oscillations in nuclei, and quasi-free propagation. We draw a distinction between $n\bar{n}$ oscillations in which the probability that a neutron transforms into an antineutron depends on time according to the sine-square law and the non-oscillatory overdamped $n\bar{n}$ conversion. We show that in all three cases decoherence due to the interaction with the environment leads to non-oscillatory evolution., Comment: 14 pages, 1 figure; v4: the title, the Abstract and Section IV are replaced, new references added, style in some places improved

Spectra of $q \bar q$ mesons are investigated in the framework of the Hamiltonian obtained from the relativistic path integral in external homogeneous magnetic field. The spectra of all 12 spin-isospin s-wave states generated by $\pi$- and $\rho$-mesons with different spin projections, are studied analytically as functions of the field strength. Three types of behavior with characteristic splittings are found. The results are in agreement with recent lattice calculations., Comment: 7 pages, 5 figures, XIIth Quark Confinement and the Hadron Spectrum, 28 Aug. - 4 Sep. 2016

The lecture presents an overview of the quest for the new physics in low energy neutron phenomena. In addition to the traditional topics the quantum damping of $n$ $\bar{n}$ oscillations is discussed., Comment: 7 pages

Spectra of $q \bar{q}$ hadrons are investigated in the framework of the Hamiltonian obtained from the relativistic path integral in external homogeneous magnetic field. The spectra of all 12 spin-isospin s-wave states, generated by $\pi$ and $\rho$ mesons with different spin projections, are studied both analytically and numerically on the lattice as functions of (magnetic field) $eB$. Results are in agreement and demonstrate three types of behavior, with characteristic splittings predicted by the theory., Comment: 29 pages, 7 figures, 1 table

We investigate the sound absorption in quark matter due to the interaction of the sound wave with the precritical fluctuations of the diquark-pair field above $T_c$. The soft collective mode of the pair field is derived using the time dependent Ginzburg-Landau functional with random Langevin forces. The strong absorption near the phase transition line may be viewed as a manifestation of the Mandelshtam-Leontovich slow relaxation time theory.

An analysis is made of the role played by the gas environment in neutron-mirror-neutron and neutron-antineutron oscillations. In the first process the interaction with the ambient medium induces a refraction energy shift which plays the role of an extra magnetic field. In the second process antineutron annihilation in practice might lead to strong decoherence, which should be taken into account in experiments with free neutrons looking for the neutron to antineutron transformation., Comment: 6 pages, no figures

We investigate the electrical conductivity(EC) of dense quark matter in the vicinity of the phase transition line. We show that: (i) At high density the Drude EC does not depend on the magnetic field up to $eB \sim 10^{19} \ G$. (ii) In the precritical region the fluctuation EC (paraconductivity) dominates over the Drude one.

This paper summarizes the relevant theoretical developments, outlines some ideas to improve experimental searches for free neutron-antineutron oscillations, and suggests avenues for future improvement in the experimental sensitivity., Comment: Submitted to Physics Reports

We briefly review the recent studies of the behavior of composite systems in magnetic field. The hydrogen atom is chosen to demonstrate the new results which may be experimentally tested. Possible applications to physics of antihydrogen are mentioned., Comment: 12 pages, 3 figures, talk at the Pomeranchuk centennial seminar, misprints corrected

Relativistic world-line Hamiltonian for strongly interacting 3q systems in magnetic field is derived from the path integral for the corresponding Green's function. The neutral baryon Hamiltonian in magnetic field obeys the pseudomomentum conservation and allows a factorization of the c.m. and internal motion. The resulting expression for the baryon mass in magnetic field is written explicitly with the account of hyperfine, OPE and OGE (color Coulomb) interaction. The neutron mass is fast decreasing with magnetic field, losing 1/2 of its value at eB~0.25 GeV^2 and is nearly zero at eB~0.5 GeV^2. Possible physical consequences of the calculated mass trajectory of the neutron, M_n(B), are presented and discussed., Comment: 29 pages, 4 figures

This report, prepared for the Community Planning Study - Snowmass 2013 - summarizes the theoretical motivations and the experimental efforts to search for baryon number violation, focussing on nucleon decay and neutron-antineutron oscillations. Present and future nucleon decay search experiments using large underground detectors, as well as planned neutron-antineutron oscillation search experiments with free neutron beams are highlighted., Comment: Report of the Community Summer Study (Snowmass 2013), Intensity Frontier -- Baryon Number Violation Group

This paper summarizes discussions of the theoretical developments and the studies performed by the NNbarX collaboration for the 2013 Snowmass Community Summer Study., Comment: A white paper for the 2013 Snowmass Community Summer Study

We study the relativistic quark-antiquark system embedded in magnetic field. The Hamiltonian containing confinement, one gluon exchange and spin-spin interaction is derived. We analytically follow the evolution of the lowest meson states as a functions of MF strength. Calculating the one gluon exchange interaction energy and spin-spin contribution we have observed, that these corrections remain finite at large magnetic fields, preventing the vanishing of the total rho-meson mass at some B_crit, as previously thought. We display the rho masses as functions of magnetic field in comparison with recent lattice data., Comment: 9 pages, 2 figures. arXiv admin note: substantial text overlap with arXiv:1210.0227

We find a new correction to the hydrogen atom ground state hyperfine energy levels splitting in magnetic field. It can be interpreted as magnetic focusing of the wave function at the origin. The effect might be within the reach of experiment., Comment: 8 pages, 3 figures

Quark--gluon matter produced in relativistic heavy--ion collisions(RHIC and LHC) is subject to a super--strong magnetic field(MF) $\sim 10^{18} - 10^{20} G$. Quark matter(QM) response to MF allows to get a new insight on its properties. We give a cursory glance on MF induced effects., Comment: Contribution to the Proceedings of "QUARKS 2012" International Seminar, Yaroslavl, June 4-10, 2012, 4 pages, no figures

We study the relativistic quark-antiquark system embedded in magnetic field (MF). The Hamiltonian containing confinement, color Coulomb and spin-spin interaction is derived. We analytically follow the evolution of the lowest neutral meson state as a function of MF strength. Calculating the color Coulomb energy $V_{Coul}$ we have observed the unbounded negative (at least in the limit of large $N_c$) contribution at large MF which makes the mass negative for $eB> eB^{QCD}_{crit}$. We display the $\pi^0$ and $\rho^0$ masses as functions of MF in comparison with recent lattice data., Comment: 16 pages, 1 figure

Heavy-ion collisions generate a huge magnetic field of the order of $10^{18} G $ for the duration of about 0.2 fm/c. This time may become an order of magnitude longer if the electrical conductivity of quark matter is large. We calculate the conductivity in the regime of high density and show that contrary to naive expectations it only weakly depends on the MF., Comment: 3 pages, 0 figures

Fermion currents in dense quark matter embedded into magnetic field are under intense discussions motivated by Chiral Magnetic Effect. We argue that conductivity of quark matter may be independent of the magnetic field direction and not proportional to the magnetic field strength., Comment: 3 pages, 0 figures

Applying the ideas and methods of condensed matter physics we calculate the quantum conductivity of quark matter in magnetic field. In strong field quantum conductivity is proportional to the square root of the field., Comment: 4 pages, Talk at the International Conference CPOD 2010

A method is presented for analysis of correlation function of two non-identical particles with strong and Coulomb interactions, resonance formation, channel coupling and spin structure. For resonance reactions we derive a formula giving the small distance contribution to the correlation function. The formalism is used to analyze the preliminary RHIC data on $\pi^{\pm} \Xi^{\mp}$ correlation measurements. The $\Xi^{*}(1530)$ resonance is successfully described. The $\pi \Xi$ source size is obtained., Comment: 21 pages, 3 figures

The analysis of the preliminary RHIC data on $\pi^{+}-\Xi^{-}$ correlation function is carried out.The $\Xi^*(1530)$ resonance is successfully described. The values of the fireball radius and of the $\pi^{+}-\Xi^{-}$ scattering lengths are obtained., Comment: Contribution to the proceedings of the XLIVth Rencontres de Moriond QCD, La Thuile, Italy, March 2009

A unique transition state is a precursor of quark matter formation. We point out the hallmarks of this state and evaluate the quark diffusion coefficient in the vicinity of the QCD critical line., Comment: 3 pages, Talk at the 15th International Seminar "Quarks-2008"

The quark diffusion coefficient in the critical window near $T_c$ and at moderate values of the chemical potential is evaluated., Comment: 2 pages, Contribution to the proceedings of the Rencontres de Moriond on QCD and Hadronic Interactions, La Thuile, Italy, March 2008

We calculate the rate of neutron-mirror-neutron oscillations for ultracold neutrons trapped in a storage vessel. Recent experimental bounds on the oscillation time are discussed., Comment: v4: typos corrected

The quark fluctuation propagator is evaluated. It defines the diffusion coefficient in the vicinity of the phase transition and the gradient term in the Ginzburg-Landau functional., Comment: Contribution to the proceedings of the Rencontres de Moriond on QCD and Hadronic Interactions, La Thuile, Italy, March 2007

We argue that there is a unique transition state of moderate density between the nuclear matter and superconducting quark matter alternatives. The distinguishing features of this state are discussed., Comment: Talk at ICHEP'06, Moscow, 26 July - 2 August 2006

We present the evidence that crossover, fluctuation phenomena and possible Anderson transition are the precursors of quark matter formation., Comment: 22 pages, 1 figure

In these lectures we discuss condensates which are formed in quark matter when it is squeezed and in a gas of fermionic atoms when it is cooled. The behavior of these two seemingly very different systems reveals striking similarities. In particular, in both systems the Bose-Einstein condensate to Bardeen--Cooper-Schrieffer (BEC-BCS) crossover takes place., Comment: Lectures delivered at 8th Moscow school of Physics (33rd ITEP Winter School of Physics)

The wave equation is derived for quark pairs in color superconductor in the regime of low density / strong coupling., Comment: 4 pages, no figures

We present a simple interpretation of the recently observed near-threshold proton-antiproton enhancement. It is described by a set of low-energy parameters deduced from the analysis of NantiN experiments at LEAR. We predict a related effect in photoproduction reaction under study by CLAS collaboration., Comment: 10 pages, 2 figures

Discussion of apparently simple issues related to the resonance close to threshold may lead to misleading results. We clarify some subtle points, in particular the relation between Breit-Wigner and effective range approaches to the f_0-a_0 mesons., Comment: LaTeX, 8 pages, no figures, minor corrections, to appear in Phys.Lett.B

We present a simple explanation for the recently observed near-threshold proton-antiproton enhancement. It is described by a set of low-energy parameters deduced from the analysis of NantiN experiments at LEAR. We predict a related effect in photoproduction reaction under study by CLAS collaboration., Comment: 8 pages, 1 figure

We have reexamined the problem of $n-\bar n$ oscillations for ultra-cold neutrons (UCN) confined within a trap. It is shown that for up to $10^3$ collisions with the walls the process can be described in terms of wave packets. The exact equation is derived describing the time-evolution of the $\bar n$-component for an arbitrary number of collisions with the trap walls. The $\bar n$-component grows linearly with time with enhancement factor depending on the reflection properties of the walls., Comment: 12 pages, 2 figures, RevTeX4, introduction rewritten and remarks added

We have reexamined the problem of $n-\bar n$ oscillations for ultra-cold neutrons (UCN) confined within a trap. We have shown that the growth of the $\bar n$ component with time is to a decent accuracy given by $P(\bar n)= \epsilon^2_{n\bar n} t_Lt,$ where $\epsilon_{n\bar n}$ is the mixing parameter, $t_L\sim 1 $ sec in the neutron propagation time between subsequent collisions with the trap walls. Possible corrections to this law and open questions are discussed., Comment: 11 pages, LaTeX2e

It is shown that the onset of the color superconducting phase occurs in the BCS-BE crossover region., Comment: 5 pages, LaTeX, references added

An introductory review of physics of color superconducting state of matter is presented. Comparison with superconductivity in electron systems reveals difficulties involved in formulating color superconductivity theory at moderately ultra-nuclear density., Comment: 17 pages, LaTeX2e, no figures

Ginzburg-Landau functional is derived for a system possessing both chiral and diquark condensates. Anderson theorem for such a system is formulated and proved., Comment: 9 pages, no figures, LaTeX2e, new discussions are added

Final state hyperon-nucleon interaction in strangeness photoproduction of the deuteron is investigated making use of the covariant reaction formalism and the P-matrix approach to the YN system. Remarkably simple analytical expression for the amplitude is obtained. Pronounced effects due to final state interaction are predicted including the manifestation of the 2.13 GeV resonance., Comment: LaTeX, 13 pages

Magnetic moment of the $\Delta^{++}$ baryon is computed within the new approach based on the QCD string Hamiltonian. The string tension $\sigma$ is only dimensionful quantity forming magnetic moments of both nucleon and $\Delta$, but color Coulomb and spin-spin interactions cancel each other in the nucleon case while in $\Delta$ they add coherently. The result $\mu_{\Delta} = 4.36\mu_N$ is in good agreement with experimental data., Comment: LaTeX, 8 pages, no figures

Strangeness photoproduction of the deuteron is investigated theoretically making use of the covariant reaction formalism and the P-matrix approach the final state hyperon-nucleon interaction. Remarkably simple analytical expression for the amplitude is obtained. Pronounced effects due to final state interaction are predicted., Comment: LaTeX, 15 pages, no figures

Magnetic moments of baryons composed of light and strange quarks are computed for the first time through the only parameter of the model -- string tension $\sigma$. Resulting theoretical values differ from the experimental ones typically by about 10%., Comment: LaTeX, 13 pages; misprints are corrected

Pronounced effects due to final state hyperon-nucleon interaction are predicted in strangeness photoproduction reaction on the deuteron. Use is made of the covariant reaction formalism and the P- matrix approach to the hyperon-nucleon interaction., Comment: LaTeX, 16 pages, 2 figures