97 research outputs found
Anomalous Transport and Generalized Axial Charge
In this paper we continue studying the modification of the axial charge in
chiral media by macroscopic helicities. Recently it was shown that magnetic
reconnections result in a persistent current of zero mode along flux tubes.
Here we argue that in general a change in the helical part of the generalized
axial charge results in the same phenomenon. Thus one may say that there is a
novel realization of chiral effects requiring no initial chiral asymmetry. The
transfer of flow helicity to zero modes is analyzed in a toy model based on a
vortex reconnection in a chiral superfluid. Then, we discuss the balance
between the two competing processes effect of reconnections and the chiral
instability on the example of magnetic helicity. We argue that in the general
case there is a possibility for the distribution of the axial charge between
the magnetic and fermionic forms at the end of the instability.Comment: 19 pages, version accepted in PR
On the Higher-Spin Spectrum in Large N Chern-Simons Vector Models
Chern-Simons gauge theories coupled to massless fundamental scalars or
fermions define interesting non-supersymmetric 3d CFTs that possess approximate
higher-spin symmetries at large N. In this paper, we compute the scaling
dimensions of the higher-spin operators in these models, to leading order in
the 1/N expansion and exactly in the 't Hooft coupling. We obtain these results
in two independent ways: by using conformal symmetry and the classical
equations of motion to fix the structure of the current non-conservation, and
by a direct Feynman diagram calculation. The full dependence on the 't Hooft
coupling can be restored by using results that follow from the weakly broken
higher-spin symmetry. This analysis also allows us to obtain some explicit
results for the non-conserved, parity-breaking structures that appear in planar
three-point functions of the higher-spin operators. At large spin, we find that
the anomalous dimensions grow logarithmically with the spin, in agreement with
general expectations. This logarithmic behavior disappears in the strong
coupling limit, where the anomalous dimensions turn into those of the critical
O(N) or Gross-Neveu models, in agreement with the conjectured 3d bosonization
duality.Comment: 52 pages, 7 figures. v3: Minor correction
On consistency of hydrodynamic approximation for chiral media
We consider chiral liquids, that is liquids consisting of massless fermions
and right-left asymmetric. In such media, one expects existence of
electromagnetic current flowing along an external magnetic field, associated
with the chiral anomaly. The current is predicted to be dissipation-free. We
consider dynamics of chiral liquids, concentrating on the issues of possible
instabilities and infrared sensitivity. Instabilities arise, generally
speaking, already in the limit of vanishing electromagnetic constant,
. In particular, liquids with non-vanishing chiral chemical
potential might decay into right-left asymmetric states containing vortices.Comment: Published versio
Chiral Vortical Effect in Superfluid
We consider rotating superfluid pionic liquid, with superfluidity being
induced by isospin chemical potential. The rotation is known to result in a
chiral current flowing along the axis of the rotation. We argue that in case of
superfluidity the chiral current is realized on fermionic zero modes
propagating along vortices. The current evaluated in this way differs by a
factor of two from the standard one. The reason is that the chiral charge is
carried by zero modes which propagate with speed of light, and thus the liquid
cannot be described by a single (local) velocity, like it is assumed in
standard derivations.Comment: 10 pages. To be published in PRD. Minor changes added; typos fixe
Coulomb corrections to the Delbrueck scattering amplitude at low energies
In this article, we study the Coulomb corrections to the Delbrueck scattering
amplitude. We consider the limit when the energy of the photon is much less
than the electron mass. The calculations are carried out in the coordinate
representation using the exact relativistic Green function of an electron in a
Coulomb field. The resulting relative corrections are of the order of a few
percent for scattering on for a large charge of the nucleus. We compare the
corrections with the corresponding ones calculated through the dispersion
integral of the pair production cross section and also with the magnetic loop
contribution to the g-factor of a bound electron. The last one is in a good
agreement with our results but the corrections calculated through the
dispersion relation are not.Comment: 8 pages, 6 figure
Serial and parallel kernelization of Multiple Hitting Set parameterized by the Dilworth number, implemented on the GPU
The NP-hard Multiple Hitting Set problem is finding a minimum-cardinality set
intersecting each of the sets in a given input collection a given number of
times. Generalizing a well-known data reduction algorithm due to Weihe, we show
a problem kernel for Multiple Hitting Set parameterized by the Dilworth number,
a graph parameter introduced by Foldes and Hammer in 1978 yet seemingly so far
unexplored in the context of parameterized complexity theory. Using matrix
multiplication, we speed up the algorithm to quadratic sequential time and
logarithmic parallel time. We experimentally evaluate our algorithms. By
implementing our algorithm on GPUs, we show the feasability of realizing
kernelization algorithms on SIMD (Single Instruction, Multiple Date)
architectures.Comment: Added experiments on one more data se
Research of ways of realization of the information interchange controller for the specialized computing module and implementation variation choice
Рассмотрена задача реализации контроллера системной магистрали для вычислительного модуля, предназначенного для использования в составе цифровой вычислительной системы семейства «Малахит». Контроллер выполнен на базе программируемой логической интегральной схемы и осуществляет сопряжение процессора серии «Мультикор», являющегося ядром модуля, с системной магистралью. Проработаны варианты реализации контроллера для конкретной приборной реализации модуля, сделаны выводы и рекомендации по их применению.The problem of implementation of the information interchange controller that is intended for the specialized computing system is discussed. The controller is implemented on programmable logic integrated circuits and provides processor of series «multicore» and information interchange interface logical connective. The ways of controller realization are researched and recommendations of efficient controller variations use are made
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