Spin Nernst effect and intrinsic magnetization in two-dimensional Dirac materials

We begin with a brief description of the role of the Nernst–Ettingshausen effect in the studies of the hightemperature superconductors and Dirac materials such as graphene. The theoretical analysis of the NE effect is involved because the standard Kubo formalism has to be modified by the presence of magnetization currents in order to satisfy the third law of thermodynamics. A new generation of the low-buckled Dirac materials is expected to have a strong spin Nernst effect that represents the spintronics analog of the NE effect. These Dirac materials can be considered as made of two independent electron subsystems of the two-component gapped Dirac fermions. For each subsystem the gap breaks a time-reversal symmetry and thus plays a role of an effective magnetic field. We explicitly demonstrate how the correct thermoelectric coefficient emerges both by the explicit calculation of the magnetization and by a formal cancelation in the modified Kubo formula. We conclude by showing that the nontrivial dependences of the spin Nersnt signal on the carrier concentration and electric field applied are expected in silicene and other low-buckled Dirac materials

The modern view on the problem of the surgical treatment of patients with pathology of the pancreas accompanied by obstructive jaundice

Catedra de chirurgie nr.2, Curs de chirurgie pediatrică, Universitatea Națională de Medicină, Odessa, Ucraina, Al XII-lea Congres al Asociației Chirurgilor „Nicolae Anestiadi” din Republica Moldova cu participare internațională 23-25 septembrie 2015Introducere: Rezultatele tratamentului chirurgical la pacienții cu patologie pancreatică pe un fundal de icter mecanic depind nu numai de cauza bolii de bază, dar de asemenea de diagnosticul oportun, durata icterului și volumul tratamentului chirurgical realizat. Scopul studiului a fost îmbunătățirea rezultatelor tratamentului chirurgical al pacienților cu sindrom de icter mecanic prin crearea unei metode de diagnostic diferențiat al patologiei de bază, cu determinarea ulterioară a volumului intervenției chirurgicale. Material și metode: Pe parcursul perioadei 2010-2015 în Clinica noastră au fost supuși tratamentului chirurgical 114 pacienți cu sindrom de icter mecanic. Algoritmul de diagnostic a inclus obigatoriu ultrasonografia, CT, MRI, FEGDS și ERCP. În unele cazuri a fost efectuată analiza genetică pentru prezența unor tipuri de mutații genice specifice. Evident pentru leziunile maligne ale pancreasului cefalic au fost verificați marcherii specifici oncogenici (CEA, CA 19-9). Cancerul de pancreas a fost confirmat la 42 (36,8%) pacienți, diferite forme de pancreatită cronică a fost găsite la 72 (63,2%) pacienți. Rezultate: Decompresia asistată laparoscopic sau cu ghidaj ultrasonografic a arborelui biliar a fost efectuată la 96 (84,2%) pacienți. La 17 pacienți cu pancreatită cronică s-a efectuat intervenție chirurgicală economă – procedeul Beger în volumul Bernese. La pacienții rămași (55) s-a efectuat rezecția pancreatoduodenală (RPD) prin metode proprii. RPD pentru cancer s-a efectuat la 42 pacienți, 7 pacienți au decedat. Rata de mortalitate a constituit 6.1%.The results of surgical treatment of patients with pathology of the pancreas on a background of jaundice is not only due to the nature of the underlying disease, but also its timely diagnosis, length of jaundice and volume of performed surgery. The aim of the study was to improve the results of surgical treatment of patients with obstructive jaundice syndrome by creating a new approach to the differential diagnostics of underlying disease with subsequent determining of the surgical intervention volume. Materials and methods_ From 2010 to 2015 in our clinic the surgical treatment of 114 patients with the obstructive jaundice syndrome was performed. The diagnostic algorithm includes the mandatory implementation of ultrasound, CT, MRI, FEGDS,ERCP. In certain cases, a genetic analysis for the presence of type-specific gene mutations was carried out. Obviously, for malignant lesions of the head of the pancreas verification of specific oncomarkers (CEA, CA 19-9) levels were estimated. Pancreatic cancer was verified in 42 (36.8%) patients, different forms of chronic pancreatitis were found in 72 (63.2%) patients. Results_ Ultrasound-guided or laparoscopy-assisted decompression of the biliary tree was performed in 96 (84.2%) patients. In17 patients with chronic pancreatitis sparing surgery in the volume of Bernese type of Beger’s procedure was done. In the rest patients (55) pancreatico-duodenal resection (PDR) by own methods was performed. PDR for cancer is performed in 42patients, 7 patients died. The mortality rate was 6.1%

Massive Spinning Particle in Any Dimension I. Integer Spins

The Kirillov-Souriau-Kostant construction is applied to derive the classical and quantum mechanics for the massive spinning particle in arbitrary dimension.Comment: 13 pages, LaTe

Quantum oscillations as the tool for study of new functional materials (Review Article)

We present an overview of our recent results on quantum magnetic oscillations in new functional materials. We begin with the Lifshitz and Kosevich approach for quasi-2D layered materials and obtain general formulas for the oscillatory parts of the grand thermodynamic potential and magnetization. Then we consider the oscillations of the Nernst–Ettingshausen coefficient which consists of thermal and magnetization parts. The difference between normal and Dirac carriers is also discussed. To conclude we consider a model for multilayer graphene which allows to calculate exactly the Berry phase which remains undetermined in the Lifshitz–Kosevich approach. The magnetic oscillations of the density of states and capacitance for different number of the carbon layers are described

BRST analysis of general mechanical systems

We study the groups of local BRST cohomology associated to the general systems of ordinary differential equations, not necessarily Lagrangian or Hamiltonian. Starting with the involutive normal form of the equations, we explicitly compute certain cohomology groups having clear physical meaning. These include the groups of global symmetries, conservation laws and Lagrange structures. It is shown that the space of integrable Lagrange structures is naturally isomorphic to the space of weak Poisson brackets. The last fact allows one to establish a direct link between the path-integral quantization of general not necessarily variational dynamics by means of Lagrange structures and the deformation quantization of weak Poisson brackets.Comment: 38 pages, misprints corrected, references and the Conclusion adde

Effective action approach and Carlson-Goldman mode in d-wave superconductors

We theoretically investigate the Carlson-Goldman (CG) mode in two-dimensional clean d-wave superconductors using the effective ``phase only'' action formalism. In conventional s-wave superconductors, it is known that the CG mode is observed as a peak in the structure factor of the pair susceptibility $S(\Omega, \mathbf{K})$ only just below the transition temperature T_c and only in dirty systems. On the other hand, our analytical results support the statement by Y.Ohashi and S.Takada, Phys.Rev.B {\bf 62}, 5971 (2000) that in d-wave superconductors the CG mode can exist in clean systems down to the much lower temperatures, $T \approx 0.1 T_c$. We also consider the manifestations of the CG mode in the density-density and current-current correlators and discuss the gauge independence of the obtained results.Comment: 23 pages, RevTeX4, 12 EPS figures; final version to appear in PR

Characteristic classes of gauge systems

We define and study invariants which can be uniformly constructed for any gauge system. By a gauge system we understand an (anti-)Poisson supermanifold provided with an odd Hamiltonian self-commuting vector field called a homological vector field. This definition encompasses all the cases usually included into the notion of a gauge theory in physics as well as some other similar (but different) structures like Lie or Courant algebroids. For Lagrangian gauge theories or Hamiltonian first class constrained systems, the homological vector field is identified with the classical BRST transformation operator. We define characteristic classes of a gauge system as universal cohomology classes of the homological vector field, which are uniformly constructed in terms of this vector field itself. Not striving to exhaustively classify all the characteristic classes in this work, we compute those invariants which are built up in terms of the first derivatives of the homological vector field. We also consider the cohomological operations in the space of all the characteristic classes. In particular, we show that the (anti-)Poisson bracket becomes trivial when applied to the space of all the characteristic classes, instead the latter space can be endowed with another Lie bracket operation. Making use of this Lie bracket one can generate new characteristic classes involving higher derivatives of the homological vector field. The simplest characteristic classes are illustrated by the examples relating them to anomalies in the traditional BV or BFV-BRST theory and to characteristic classes of (singular) foliations.Comment: 23 pages, references added, typos correcte

Wick type deformation quantization of Fedosov manifolds

A coordinate-free definition for Wick-type symbols is given for symplectic manifolds by means of the Fedosov procedure. The main ingredient of this approach is a bilinear symmetric form defined on the complexified tangent bundle of the symplectic manifold and subject to some set of algebraic and differential conditions. It is precisely the structure which describes a deviation of the Wick-type star-product from the Weyl one in the first order in the deformation parameter. The geometry of the symplectic manifolds equipped by such a bilinear form is explored and a certain analogue of the Newlander-Nirenberg theorem is presented. The 2-form is explicitly identified which cohomological class coincides with the Fedosov class of the Wick-type star-product. For the particular case of K\"ahler manifold this class is shown to be proportional to the Chern class of a complex manifold. We also show that the symbol construction admits canonical superextension, which can be thought of as the Wick-type deformation of the exterior algebra of differential forms on the base (even) manifold. Possible applications of the deformed superalgebra to the noncommutative field theory and strings are discussed.Comment: 20 pages, no figure

Quantum phase transitions from topology in momentum space

Many quantum condensed matter systems are strongly correlated and strongly interacting fermionic systems, which cannot be treated perturbatively. However, physics which emerges in the low-energy corner does not depend on the complicated details of the system and is relatively simple. It is determined by the nodes in the fermionic spectrum, which are protected by topology in momentum space (in some cases, in combination with the vacuum symmetry). Close to the nodes the behavior of the system becomes universal; and the universality classes are determined by the toplogical invariants in momentum space. When one changes the parameters of the system, the transitions are expected to occur between the vacua with the same symmetry but which belong to different universality classes. Different types of quantum phase transitions governed by topology in momentum space are discussed in this Chapter. They involve Fermi surfaces, Fermi points, Fermi lines, and also the topological transitions between the fully gapped states. The consideration based on the momentum space topology of the Green's function is general and is applicable to the vacua of relativistic quantum fields. This is illustrated by the possible quantum phase transition governed by topology of nodes in the spectrum of elementary particles of Standard Model.Comment: 45 pages, 17 figures, 83 references, Chapter for the book "Quantum Simulations via Analogues: From Phase Transitions to Black Holes", to appear in Springer lecture notes in physics (LNP

Exploration of the equilibrium operating space for NSTX-Upgrade

This paper explores a range of high-performance equilibrium scenarios available in the NSTX-Upgrade device [J.E. Menard, submitted for publication to Nuclear Fusion]. NSTX-Upgrade is a substantial upgrade to the existing NSTX device [M. Ono, et al., Nuclear Fusion 40, 557 (2000)], with significantly higher toroidal field and solenoid capabilities, and three additional neutral beam sources with significantly larger current drive efficiency. Equilibria are computed with freeboundary TRANSP, allowing a self consistent calculation of the non-inductive current drive sources, the plasma equilibrium, and poloidal field coil current, using the realistic device geometry. The thermal profiles are taken from a variety of existing NSTX discharges, and different assumptions for the thermal confinement scalings are utilized. The no-wall and idealwall n=1 stability limits are computed with the DCON code. The central and minimum safety factors are quite sensitive to many parameters: they generally increases with large outer plasmawall gaps and higher density, but can have either trend with the confinement enhancement factor. In scenarios with strong central beam current drive, the inclusion of non-classical fast ion diffusion raises qmin, decreases the pressure peaking, and generally improves the global stability, at the expense of a reduction in the non-inductive current drive fraction; cases with less beam current drive are largely insensitive to additional fast ion diffusion. The non-inductive current level is quite sensitive to the underlying confinement and profile assumptions. For instance, for BT=1.0 T and Pinj=12.6 MW, the non-inductive current level varies from 875 kA with ITER-98y,2 thermal confinement scaling and narrow thermal profiles to 1325 kA for an ST specific scaling expression and broad profiles. This sensitivity should facilitate the determination of the correct scaling of transport with current and field to use for future fully non-inductive ST devices. Scenarios are presented which can be sustained for 8-10 seconds, or (20-30)τCR, at βN=3.8-4.5, facilitating, for instance, the study of disruption avoidance for very long pulse. Scenarios have been documented which can operate with βT~25% and equilibrated qmin>1. The value of qmin can be controlled at either fixed non-inductive fraction of 100% or fixed plasma current, by varying which beam sources are used, opening the possibility for feedback qmin control. In terms of quantities like collisionality, neutron emission, non-inductive fraction, or stored energy, these scenarios represent a significant performance extension compared to NSTX and other present spherical torii