Schwinger pair creation in Dirac semimetals in the presence of external magnetic and electric fields

We discuss the Schwinger pair creation process for the system of massless Dirac fermions in the presence of constant external magnetic and electric fields. The pair production rate remains finite unlike the vacuum decay rate. In the recently discovered Dirac semimetals, where the massless Dirac fermions emerge, this pair production may be observed experimentally through the transport properties. We estimate its contribution to the ordinary conductivity of the semimetals.Comment: Latex, 8 page

Effect of interactions on the topological expression for the chiral separation effect

In the absence of interactions the conductivity of chiral separation effect (CSE) in the system of massless fermions is given by topological expression. Interactions might change the pattern drastically. However, we prove that the CSE conductivity is still given by the topological invariant composed of the Green functions at zero temperature as long as the chiral symmetry is present, and if the renormalized axial current is considered. This allows to predict its appearance with the standard value of conductivity per Dirac fermion $\sigma_{CSE} = \frac{1}{2 \pi^2}$ in quark - gluon matter at $T = 0$ and sufficiently large baryon chemical potential, in the hypothetical phase with restored chiral symmetry and without color superconductivity. This phase may be realized inside the neutron stars. We also argue that the same topological expression for the CSE may be observed in Weyl semimetals, which realize the system of interacting relativistic fermions in solid state systems. In order to estimate the non - perturbative corrections to $\sigma_{CSE}$ within QCD at finite temperatures we apply method of field correlators developed by Yu.A.Simonov. As expected, above the deconfinement crossover the topological expression is approached within the quark - gluon plasma phase, when the quark chemical potential is sufficiently large. However, we observe that this occurs only when quark chemical potential is much larger than the thermal (Debye) mass. This range of parameters appears to be far out of the region accessible at the modern colliders.Comment: Latex, 21 pages, 4 figure

Josephson φ\varphi-junctions based on structures with complex normal/ferromagnet bilayer

We demonstrate that Josephson devices with nontrivial phase difference $0<\varphi_g <\pi$ in the ground state can be realized in structures composed from longitudinally oriented normal metal (N) and ferromagnet (F) films in the weak link region. Oscillatory coupling across F-layer makes the first harmonic in the current-phase relation relatively small, while coupling across N-layer provides negative sign of the second harmonic. To derive quantitative criteria for a $\varphi$-junction, we have solved two-dimensional boundary-value problem in the frame of Usadel equations for overlap and ramp geometries of S-NF-S structures. Our numerical estimates show that $\varphi$-junctions can be fabricated using up-to-date technology.Comment: 14 pages, 9 figure

Schwinger pair creation in multilayer graphene

The low energy effective field model for the multilayer graphene (at ABC stacking) in external Electric field is considered. The Schwinger pair creation rate and the vacuum persistence probability are calculated using the semi - classical approach.Comment: Latex, 5 pages, accepted for publication in JETP let

SHORT-TERM RESULTS OF SIMULTANEOUS SURGERIES AT METASTATIC COLORECTAL CANCER

We compared the main group of patients (64 persons) underwent colon resection and liver resection, radiofrequency ablation of metastases in the liver and portal vein chemoembolization with the control group (62 persons) with the operation on the colon without intervention on the liver. The blood loss during surgery in the main group was 696.1 ± 226.3 ml and in the control group - 473.3 ± 245.9 ml (p = 0.000008). When performing hemihepatectomy blood loss during surgery was 802.9 ± 208.5 ml, and performing other liver resections - 575 ± 182.2 ml (p = 0.00005). Duration of hospital stay after the surgery in the study group was 16.8 ± 5.1 days and in the control group -14.0 ± 4.1 days (p = 0,001). Duration of hospital stay after the surgery was higher in the patients after hemihepatectomy, compared to the patients who received smaller volume liver resection -19.7 ± 3.9 versus 13.4 ± 3.8 days (p = 0,005). Postoperative complications were more frequent in the patients of the main group -18 (28.1 %) vs 10 (16.1 %). However, increasing the proportion of complications in the patients with simultaneous treatment of complications associated with the summation operations on the colon and liver operations. Performing liver resection is an independent factor contributing to the prolongation of operative time and blood loss, which increases the frequency of postoperative complications and increases duration of the patient's stay in the hospital

Fermi point in graphene as a monopole in momentum space

We consider the effective field theory of graphene monolayer with the Coulomb interaction between fermions taken into account. The gauge field in momentum space is introduced. The position of the Fermi point coincides with the position of the corresponding monopole. The procedure of extracting such monopoles during lattice simulations is suggested.Comment: Latex, 12 page

Automated test system of diesel engines based on fuzzy neural network

© Medwell Journals, 2014. This study deals with the method for controlling a test stand of diesel engines based on fuzzy neural network. Structure and training algorithm have been proposed for a fuzzy neural network to control a diesel engine during testing. A knowledge base structure has been proposed. Fuzzy rules have been described to control a diesel engine. Techniques and algorithms have been realized in the form of a computer program. The effectiveness of the proposed automated diesel engine test system has been analyzed

Nambu monopoles in lattice Electroweak theory

We considered the lattice electroweak theory at realistic values of $\alpha$ and $\theta_W$ and for large values of the Higgs mass. We investigated numerically the properties of topological objects that are identified with quantum Nambu monopoles. We have found that the action density near the Nambu monopole worldlines exceeds the density averaged over the lattice in the physical region of the phase diagram. Moreover, their percolation probability is found to be an order parameter for the transition between the symmetric and the broken phases. Therefore, these monopoles indeed appear as real physical objects. However, we have found that their density on the lattice increases with increasing ultraviolet cutoff. Thus we conclude, that the conventional lattice electroweak theory is not able to predict the density of Nambu monopoles. This means that the description of Nambu monopole physics based on the lattice Weinberg - Salam model with finite ultraviolet cutoff is incomplete. We expect that the correct description may be obtained only within the lattice theory that involves the description of TeV - scale physics.Comment: LATE