We study heating and dissipation effects in granular nanosystems in the regime of weak coupling between the grains. We focus on the cotunneling regime and solve the heat-dissipation problem in an array of grains exactly. We show that the power to heat ratio has a universal quantized value, which is geometrically protected: it depends only on the number of grains.

N. M. Chtchelkatchev A. Glatz I. S. Beloborodov

We study electron transport in granular film placed above the ferroelectric substrate. We show that the conductivity of granular film strongly depends on the ferroelectric state due to screening effects which modify the Coulomb blockade in granular film. In particular, the electric current in granular film is controlled by the direction of ferroelectric polarization. We show that the ferroelectric/granular film system has a large electro-resistance effect. This effect can be utilized in memory and electric field sensor applications.

O. G. Udalov N. M. Chtchelkatchev I. S. Beloborodov

The technique of discrimination of the $e^+e^-\to e^+e^-$ and $e^+e^-\to \pi^+\pi^-$ events in energy range $0.5 < \sqrt{s} < 1$ GeV by energy deposition in the calorimeter of SND detector was developed by applying machine learning method. Identification efficiency for $e^+e^-\to e^+e^-$ and $e^+e^-\to \pi^+\pi^-$ events in the range from 99.3 to 99.8 % has been achived.

M. N. Achasov K. I. Beloborodov A. S. Kupich

The persistent radio counterpart of FRB 121102 is estimated to have $N\sim 10^{52}$ particles, energy $E_N\sim 10^{48}$ erg, and size $R\sim 10^{17}$ cm. The source can be a nebula inflated and heated by an intermittent outflow from a magnetar --- a neutron star powered by its magnetic (rather than rotational) energy. The object is young and frequently liberating energy in magnetic flares driven by accelerated ambipolar diffusion in the neutron star core, feeding the nebula and producing bright millisecond bursts. The particle number in the nebula is consistent with ion ejecta from giant flares. The nebula may also contain the freeze-out of electron-positron pairs $N_\pm\sim 10^{51}$ created months after the neutron star birth; the same mechanism offers an explanation for $N_\pm$ in the Crab nebula. The persistent source around FRB 121102 is likely heated by magnetic dissipation and internal waves excited by the magnetar ejecta. The volumetric heating by waves explains the nebula's enormous efficiency in producing radio emission. The repeating radio bursts are suggested to occur much closer to the magnetar, whose flaring magnetosphere drives ultrarelativistic internal shocks into the magnetar wind. The shocks are mediated by Larmor rotation that forms a GHz maser with the observed ms duration. Furthermore, the flare ejecta can become charge-starved and then convert to electromagnetic waves.

Andrei M. Beloborodov

Udalov and Beloborodov in the recent papers [Phys. Rev. B 95, 134106 (2017); Phys. Rev. B 96, 125425 (2017)] report the strong influence of image forces on the conductance of ferroelectric tunnel junctions. In particular, the authors state that there is enhancement of the electroresistance effect due to polarization hysteresis in symmetric tunnel junctions at nonzero bias. This conjecture seems to be a breakthrough --- the common knowledge is that the considerable effect, linear over voltage bias, takes place only in NONsymmetric junctions. We show that the influence of image forces on the conductance of ferroelectric tunnel junctions is highly overestimated due to neglecting the difference between characteristic ferroelectric relaxation and electron tunneling times. We argue that notable enhancement of the electroresistance effect from image forces due to polarization hysteresis in symmetric tunnel junctions at nonzero bias might be observed only at anomalously slow electron tunneling through the barrier. The same applies to magnetic tunnel junctions with a ferroelectric barrier also considered by Udalov et al: there is no significant increase of the magnetoelectric effect due to image forces for typical electron tunneling times. Udalov and Beloborodov completely missed the development of image force theory since 1950's and they forgot that electrons move much faster than atoms in condensed matter. We underline that taking into account dynamical effects in charge tunneling can bring new insight on physics of ferroelectric tunnel junctions.

N. M. Chtchelkatchev A. V. Mikheyenkov

The e+e- -> pi0 pi0 gamma process was studied in the SND experiment at VEPP-2M e+e- collider in the energy region 0.60-0.97 GeV. From the analysis of the energy dependence of measured cross section the branching ratios B(omega -> pi0 pi0 gamma)= (6.6 +1.4-0.8(stat) +-0.6(syst))x10^-5 and B(rho -> pi0 pi0 gamma)=(4.1 +1.0-0.9(stat) +-0.3(syst))x10^-5 were obtained.

M. N. Achasov K. I. Beloborodov A. V. Berdyugin A. G. Bogdanchikov A. V. Bozhenok D. A. Bukin S. V. Burdin A. V. Vasiljev V. B. Golubev T. V. Dimova V. P. Druzhinin V. N. Ivanchenko A. A. Korol I. A. Koop S. V. Koshuba A. V. Otboev E. V. Pakhtusova A. A. Salnikov S. I. Serednyakov V. A. Sidorov Z. K. Silagadze A. N. Skrinsky A. G. Skripkin Yu. V. Usov V. V. Shary Yu. M. Shatunov

We study Coulomb blockade (CB) oscillations in the thermodynamics of a metallic grain which is connected to a lead by a tunneling contact with a large conductance $g_0$ in a wide temperature range, $E_Cg_0^4 e^{-g_0/2}<T<E_C$, where $E_C$ is the charging energy. Using the instanton analysis and the renormalization group we obtain the temperature dependence of the amplitude of CB oscillations which differs from the previously obtained results. Assuming that at $T < E_Cg_0^4 e^{-g_0/2}$ the oscillation amplitude weakly depends on temperature we estimate the magnitude of CB oscillations in the ground state energy as $E_Cg_0^4 e^{-g_0/2}$.

I. S. Beloborodov A. V. Andreev A. I. Larkin

Standard GRB fireballs must carry free neutrons. This crucially changes the mechanism of fireball deceleration by an external medium. As the ion fireball decelerates, the coasting neutrons form a leading front. They gradually decay, leaving behind a relativistic trail of decay products mixed with the ambient medium. The ion fireball sweeps up the trail and drives a shock wave in it. Thus, observed afterglow emission is produced in the neutron trail. The impact of neutrons turns off at 10^{17}cm from the explosion center, and here a spectral transition is expected in GRB afterglows. Absence of neutron signatures would point to absence of baryons and a dominant Poynting flux in the fireballs.

Andrei M. Beloborodov

A rotating star with a monopole (or split monopole) magnetic field gives the simplest, prototype model of a rotationally driven stellar wind. Winds from compact objects, in particular neutron stars, carry strong magnetic fields with modest plasma loading, and develop ultra-relativistic speeds. We investigate the relativistic wind launched from a dense, gravitationally bound, atmosphere on the stellar surface. We first examine the problem analytically and then perform global kinetic plasma simulations. Our results show how the wind acceleration mechanism changes from centrifugal (magnetohydrodynamic) to electrostatic (charge-separated) depending on the parameters of the problem. The two regimes give winds with different angular distributions and different scalings with the magnetization parameter.

Rui Hu Andrei M. Beloborodov Alexander Y. Chen

In the innermost region of the advective accretion disk orbiting a black hole of high spin, the inertia of heat stored in the accreting gas is comparable to that of the gas rest mass itself. Accounting for this effect, we derive additional terms in the disk structure equations, and show that the heat inertia plays a significant role in the global energy conservation and dynamics of accretion in the relativistic advective disks.

A. M. Beloborodov M. A. Abramowicz I. D. Novikov