4,524 research outputs found
Lattice field theory simulations of Dirac semimetals
In this paper the observed Dirac semimetals NaBi and CdAs are
studied within lattice simulation. We formulate lattice field theory with
rooted staggered fermions on anisotropic lattice. It is shown that in the limit
of zero temporal lattice spacing this theory reproduces low energy effective
theory of Dirac semimetals. Using this lattice theory we study the phase
diagram of Dirac semimetals in the plane effective coupling constant--Fermi
velocity anisotropy. Within the formulated theory the results are practically
volume independent in contrast with our previous study. Our results confirm our
previous finding that within the Dirac model with bare Coulomb interaction both
NaBi and CdAs lie deep in the insulator phase.Comment: 11 pages, 5 figures, 2 tables, typo in Eq. (20) corrected, Appendix
adde
Catalysis of Dynamical Chiral Symmetry Breaking by Chiral Chemical Potential in Dirac semimetals
In this paper we study how dynamical chiral symmetry breaking is affected by
nonzero chiral chemical potential in Dirac semimetals. To perform this study we
applied lattice quantum Monte Carlo simulations of Dirac semimetals. Within
lattice simulation we calculated the chiral condensate for various fermion
masses, the chiral chemical potentials and effective coupling constants. For
all parameters under consideration we have found that the chiral condensate is
enhanced by chiral chemical potential. Thus our results confirms that in Dirac
semimetals the chiral chemical potential plays a role of the catalyst of the
dynamical chiral symmetry breaking.Comment: 11 pages, 3 figure
Lattice Quantum Monte Carlo Study of Chiral Magnetic Effect in Dirac Semimetals
In this paper Chiral Magnetic Effect (CME) in Dirac semimetals is studied by
means of lattice Monte Carlo simulation. We measure conductivity of Dirac
semimetals as a function of external magnetic field in parallel
and perpendicular to the external field
directions. The simulations are carried out in three regimes: semimetal phase,
onset of the insulator phase and deep in the insulator phase. In the semimetal
phase grows whereas drops with magnetic
field. Similar behaviour was observed in the onset of the insulator phase but
conductivity is smaller and its dependence on magnetic field is weaker. Finally
in the insulator phase conductivities are close to
zero and do not depend on magnetic field. In other words, we observe
manifestation of the CME current in the semimetal phase, weaker manifestation
of the CME in the onset of the insulator phase. We do not observe signatures of
CME in the insulator phase. We believe that the suppression of the CME current
in the insulator phase is connected to chiral symmetry breaking and generation
of dynamical fermion mass which take place in this phase.Comment: 6 pages, 4 figure
Tunable Integrated-Optics Nanoscaled Devices Based on Magnetic Photonic Crystals
Magnetooptical properties of magnetic photonic crystals have been
investigated in the view of their possible applications for the modern
integrated-optics devices. A "transfer matrices" formalism was expanded for the
case of oblique light incidence on the periodic nanoscaled magnetic
multilayered systems. Several new effects such as the Faraday effect dependence
on the incidence angle and the tunability of the bandgap defect modes spectral
location by external magnetic fields were found. Several possibilities of
one-dimensional magnetic photonic crystals applications for the optical devices
are discussed. Initial steps towards the practical implementation of the
proposed devices are reported.Comment: Submitted on behalf of TIMA Editions
(http://irevues.inist.fr/tima-editions
A study of the temperature dependence of bienzyme systems and enzymatic chains
It is known that most enzyme-facilitated reactions are highly temperature dependent processes. In general, the temperature coefficient, Q10, of a simple reaction reaches 2.0-3.0. Nevertheless, some enzyme-controlled processes have much lower Q10 (about 1.0), which implies that the process is almost temperature independent, even if individual reactions involved in the process are themselves highly temperature dependent. In this work, we investigate a possible mechanism for this apparent temperature compensation: simple mathematical models are used to study how varying types of enzyme reactions are affected by temperature. We show that some bienzyme-controlled processes may be almost temperature independent if the modules involved in the reaction have similar temperature dependencies, even if individually, these modules are strongly temperature dependent. Further, we show that in non-reversible enzyme chains the stationary concentrations of metabolites are dependent only on the relationship between the temperature dependencies of the first and last modules, whilst in reversible reactions, there is a dependence on every module. Our findings suggest a mechanism by which the metabolic processes taking place within living organisms may be regulated, despite strong variation in temperature
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