583 research outputs found
Color-flavor locked superconductor in a magnetic field
We study the effects of moderately strong magnetic fields on the properties
of color-flavor locked color superconducting quark matter in the framework of
the Nambu-Jona-Lasinio model. We find that the energy gaps, which describe the
color superconducting pairing as well as the magnetization, are oscillating
functions of the magnetic field. Also, we observe that the oscillations of the
magnetization can be so strong that homogeneous quark matter becomes metastable
for a range of parameters. We suggest that this points to the possibility of
magnetic domains or other types of magnetic inhomogeneities in the quark cores
of magnetars.Comment: 12 pages, 3 figures. Version accepted for publication in Phys. Rev.
Absence of the London limit for the first-order phase transition to a color superconductor
We study the effects of gauge-field fluctuations on the free energy of a
homogeneous color superconductor in the color-flavor-locked (CFL) phase.
Gluonic fluctuations induce a strong first-order phase transition, in contrast
to electronic superconductors where this transition is weakly first order. The
critical temperature for this transition is larger than the one corresponding
to the diquark pairing instability. The physical reason is that the gluonic
Meissner masses suppress long-wavelength fluctuations as compared to the normal
conducting phase where gluons are massless, which stabilizes the
superconducting phase. In weak coupling, we analytically compute the
temperatures associated with the limits of metastability of the normal and
superconducting phases, as well as the latent heat associated with the
first-order phase transition. We then extrapolate our results to intermediate
densities and numerically evaluate the temperature of the fluctuation-induced
first-order phase transition, as well as the discontinuity of the diquark
condensate at the critical point. We find that the London limit of magnetic
interactions is absent in color superconductivity.Comment: 14 pages, 5 figure
Integral functions of electron lateral distribution and their fluctuations in electron-photon cascades
Monte Carlo simulated lateral distribution functions for electrons of EPC developing in lead, at superhigh energies (.1-1 PeV) for depths t or = 60 c.u. delta t=1t. c.u. are presented. The higher moment characteristics, i.e., variation, asymmetry, excess, are presented along with analytical solutions for the same characteristics at fixed observation level calculated to theory approximations A and B by using numerical inversion of the Laplace transformation. The conclusion is made of a complex, usually non-Gaussian shape of the function of the particle number distribution within a circle of given radius at fixed depth
Analytical-numerical methods of calculations of energy and three-dimensional particle distributions in electromagnetic cascades
Analytical and numerical methods of calculation of the energy and three dimensional EPS characteristics are reported. The angular and lateral functions of electrons in EPS have been obtained by the Landau and small angle approximations A and B and compared with earlier data. A numerical method of solution of cascade equations for the EPS distribution function moments has been constructed. Considering the equilibrium rms angle as an example, errors appearing when approximating the elementary process cross sections by their asymptotic expressions are analyzed
Sensitivity of depth of maximum and absorption depth of EAS to hadron production mechanism
Comparison of experimental data on depth of extensive air showers (EAS) development maximum in the atmosphere, T sub M and path of absorption, lambda, in the lower atmosphere of EAS with fixed particle number in the energy region eV with the results of calculation show that these parameters are sensitive mainly to the inelastic interaction cross section and scaling violation in the fragmentation and pionization region. The data are explained in a unified manner within the framework of a model in which scaling is violated slightly in the fragmentation region and strongly in the pionization region at primary cosmic rays composition close to the normal one and a permanent increase of inelastic interaction cross section. It is shown that, while interpreting the experimental data, disregard of two methodical points causes a systematic shift in T sub M: (1) shower selection system; and (2) EAS electron lateral distribution when performing the calculations on basis of which the transfer is made from the Cerenkov pulse FWHM to the depth of shower maximum, T sub M
Fundamental bounds on transmission through periodically perforated metal screens with experimental validation
This paper presents a study of transmission through arrays of periodic
sub-wavelength apertures. Fundamental limitations for this phenomenon are
formulated as a sum rule, relating the transmission coefficient over a
bandwidth to the static polarizability. The sum rule is rigorously derived for
arbitrary periodic apertures in thin screens. By this sum rule we establish a
physical bound on the transmission bandwidth which is verified numerically for
a number of aperture array designs. We utilize the sum rule to design and
optimize sub-wavelength frequency selective surfaces with a bandwidth close to
the physically attainable. Finally, we verify the sum rule and simulations by
measurements of an array of horseshoe-shaped slots milled in aluminum foil.Comment: 10 pages, 11 figures. Updated Introduction and Conclusion
Bulk viscosity of spin-one color superconductors with two quark falvors
We consider the contribution of the Urca-type processes to the bulk viscosity
of several spin-one color-superconducting phases of dense two-flavor quark
matter. In the so-called transverse phases which are suggested to be
energetically favorable at asymptotic densities, the presence of ungapped
quasiparticle modes prevents that spin-one color superconductivity has a large
effect on the bulk viscosity. When all modes are gapped, as for one particular
color-spin-locked phase, the effect on the viscosity can be quite large, which
may have important phenomenological implications.Comment: 10 pages, 6 figures, Discussion is extended and several references
added. Version accepted for publication in Phys. Rev.
Gluonic phases, vector condensates, and exotic hadrons in dense QCD
We study the dynamics in phases with vector condensates of gluons (gluonic
phases) in dense two-flavor quark matter. These phases yield an example of
dynamics in which the Higgs mechanism is provided by condensates of gauge (or
gauge plus scalar) fields. Because vacuum expectation values of spatial
components of vector fields break the rotational symmetry, it is naturally to
have a spontaneous breakdown both of external and internal symmetries in this
case. In particular, by using the Ginzburg-Landau approach, we establish the
existence of a gluonic phase with both the rotational symmetry and the
electromagnetic U(1) being spontaneously broken. In other words, this phase
describes an anisotropic medium in which the color and electric
superconductivities coexist. It is shown that this phase corresponds to a
minimum of the Ginzburg-Landau potential and, unlike the two-flavor
superconducting (2SC) phase, it does not suffer from the chromomagnetic
instability. The dual (confinement) description of its dynamics is developed
and it is shown that there are light exotic vector hadrons in the spectrum,
some of which condense. Because most of the initial symmetries in this system
are spontaneously broken, its dynamics is very rich.Comment: 33 pages, RevTeX; v.2: Published PRD versio
Фізико-механічні характеристики нанокомпозційниих матеріалів на основі фторопласту
In this work, the elastic and strength properties of polymer composites with a polytrifluorochlorethylene matrix and a thermally expanded graphite filler were evaluated by the nanoindentation method, and the effect of the dispersion and concentration of the filler on the mechanical characteristics of nanocomposite materials was considered. It is shown that the microhardness of nanocomposite materials decreases with increasing filler concentration. An increase in the microhardness and Young's modulus with the growth of filler particles was observed for nanocomposite materials with a filler concentration of 3 vol.%. As for nanocomposite materials with a filler volume fraction of 10 vol.%, similar behavior of the mechanical characteristics was observed with an increase in the dispersion of thermally expanded graphite particles to 180 μm. A subsequent increase in the average particle size of thermally expanded graphite leads to a decrease in Young's modulus and microhardness of composites, which may be associated with different degrees of polymer structuring and the formation of different orientational orders from the filler. The observed changes in Young's modulus and H/E ratio indicate a change in the amorphous crystalline behavior of the composite to that characteristic of fine-crystalline materials and depends on the dispersion of thermally expanded graphite.
Pages of the article in the issue: 107 - 110
Language of the article: UkrainianУ даній роботі методом наноіндентування було проведено оцінку пружних і міцнісних властивостей полімерних композитів з політрифторхлоретиленовою матрицею і наповнювачем з термічно розширеного графіту. Розглянуто вплив дисперсності і концентрації наповнювача на механічні характеристики нанокомпозиційних матеріалів. Показано, що мікротвердість нанокомпозиційних матеріалів зменшується зі збільшенням концентрації наповнювача. Спостережувані при цьому зміни модуля Юнга і співвідношення H/E свідчать про зміну аморфно кристалічної поведінки композиту до такої, що характерна дрібнокристалічним матеріалам в залежності від дисперсності розширеного графіту
Spinor Field in Bianchi type-I Universe: regular solutions
Self-consistent solutions to the nonlinear spinor field equations in General
Relativity has been studied for the case of Bianchi type-I (B-I) space-time. It
has been shown that, for some special type of nonliearity the model provides
regular solution, but this singularity-free solutions are attained at the cost
of broken dominant energy condition in Hawking-Penrose theorem. It has also
been shown that the introduction of -term in the Lagrangian generates
oscillations of the B-I model, which is not the case in absence of
term. Moreover, for the linear spinor field, the term provides
oscillatory solutions, those are regular everywhere, without violating dominant
energy condition.
Key words: Nonlinear spinor field (NLSF), Bianch type -I model (B-I),
term
PACS 98.80.C CosmologyComment: RevTex, 21 page
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