Volume 103, Nº 2 (2016)

In the case of using the higher derivative regularization for N = 1 supersymmetric quantum electrodynamics (SQED) with N_f flavors, the loop integrals giving the β-function are integrals of double total derivatives in themomentum space. This feature allows reducing one of the loop integrals to an integral of the δ-function and deriving the Novikov–Shifman–Vainshtein–Zakharov relation for the renormalization group functions defined in terms of the bare coupling constant. We consider N = 1 SQED with N_f flavors regularized by the dimensional reduction in the \(\overline {DR} \)-scheme. Evaluating the scheme-dependent three-loop contribution to the β-function proportional to (N_f)² we find the structures analogous to integrals of the δ-singularities. After adding the schemeindependent terms proportional to (N_f)¹, we obtain the known result for the three-loop β-function.

A significant (to 12 ps) decrease in the lifetime of excited states of quantum emitters in the form of three-layer colloidal quantum dots (CdSe/CdS/ZnS) placed in an aluminum–triangular silver nanoprism cavity (patch nanoantenna) has been experimentally demonstrated. The decrease in the time of spontaneous emission of quantum dots has been explained by the Purcell effect. The Purcell coefficient for an emitter in the resonator has been found to be 625. Such a significant increase in the rate of spontaneous emission in the patch nanoantenna is due to an increase in the local density of photon states in the plasmonic cavity.

Molecular dynamics experiments for metal nanoclusters (gold, nickel, and aluminum) with the tight-binding potential have indicated that the melting temperature increases noticeably and the crystallization temperature decreases significantly with an increase in the absolute value of the heating and cooling rates, respectively. It has been concluded that the pronounced hysteresis of melting and crystallization is due primarily to nonequilibrium conditions of heating and cooling, but it is incompletely eliminated by reducing the rate of variation of the temperature. It has been found that the hysteresis of melting and crystallization corresponds at the structural level to a smooth crossover from the liquid state to the crystal one.

A small difference between the rhombohedral phosphorus lattice (A-7 phase) and the simple cubic phase, as well as between phosphorene and the cubic structure, is used in order to construct their quasiparticle band dispersion. We exploit the Peierls idea of the Brillouin zone doubling/folding, which has been previously employed in consideration of semimetals of the V period and IV–VI semiconductors. In a common framework, individual properties of phosphorus allotropes are revealed.

We consider the spin-1/2 model on the honeycomb lattice [A. Kitaev, Ann. Phys. 321, 2 (2006)] in the presence of a weak magnetic field h_α ≪ J. Such a perturbation treated in the lowest nonvanishing order over h_α leads [K.S. Tikhonov, M.V. Feigel’man, and A.Yu. Kitaev, Phys. Rev. Lett. 106, 067203 (2011)] to a powerlaw decay of irreducible spin correlations 《s^z(t, r)s^z(0, 0)》 ∝ h_z²f(t, r), where f(t, r) ∝ [max(t, Jr)]^–4. We have studied the effects of the next order of perturbation in h_z and found an additional term of the order h_z⁴ in the correlation function 《s^z(t, r)s^z(0, 0)》 which scales as h_z⁴cosγ/r³ at Jt≪ r, where γ is the polar angle in the 2D plane. We demonstrate that such a contribution can be understood as a result of a perturbation of the effective Majorana Hamiltonian by the weak imaginary vector potential A_x ∝ ih_z².

We investigate the electronic structure of the two-dimensional t–J model in a transverse external static magnetic field with canted long-range magnetic order using cluster perturbation theory. The distribution of the spectral weight in the whole range of fields from zero to ferromagnetic saturation is explored. We demonstrate the possibility of a sharp change in a distribution of spectral weight at the Fermi level associated with the magnetic correlations when varying magnetic field.

New features of the MCSANC v.1.20 program, a Monte Carlo tool for calculation of the next-to-leading order electroweak and QCD corrections to various Standard Model processes, have been presented. The extensions concern implementation of Drell–Yan-like processes and include a systematic treatment of the photon-induced contribution in proton–proton collisions and electroweak corrections beyond the NLO approximation. There are also technical improvements such as calculation of the forward–backward asymmetry for the neutral current Drell–Yan process. The updated code is suitable for studies of the effects due to EW and QCD radiative corrections to Drell–Yan (and several other) processes at the LHC and for forthcoming high-energy proton–proton colliders.

Chiral anomaly observed in the chiral superfluid ³He-A is the result of the combined effect of the real space and momentum space topologies. This effect incorporates several topological charges in the extended (k, r)- space, which is beyond the conventional chiral anomaly in the relativistic systems.