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A. A. Ivanov

Publications and source records attributed to A. A. Ivanov.

50 records · Page 3Linked to original sources
arXiv2006

Recent results from Yakutsk experiment: development of EAS, energy spectrum and primary particle mass composition in the energy region of 10^15-10^19 eV

Experimental data obtained at the Yakutsk array after the modernization in 1993 are analyzed. The characteristics of EAS longitudinal and radial development found from the charged particle flux and EAS Cherenkov light registered at the Yakutsk complex array are presented. The energy spectrum of EAS obtained from Cherenkov light and an estimate of the PCR mass composition are presented.

astro-ph↗
arXiv2005

Fluctuations of Xmax and Primary Particle Mass Composition in the Range of Energy 5 10^{17} - 3 10^{19} ev by Yakutsk Data

The experimental distributions of $\Xmax$ obtained with the Yakutsk EAS array at fixed energies of $5 \times10^{17}$, $1\times10^{18}$ and $5\times10^{18}$ eV are analysed. A recent version of the QGSJET model is used as a tool of our analysis. In the framework of this model, the most adequate mass composition of primary particles satisfying the experimental data on $\Xmax$ is selected.

astro-ph↗
arXiv2005

Influence of Primary Cosmic Radiation Mass Composition on the Estimation of Eas Energy

At the Yakutsk EAS array E_em is determined by using measurements of EAS Cherenkov light flux and charged particle flux. It is known from calculations that these characteristics depend on a sort of primary particle and, therefore, the estimation of E_em depends on a primary particle mass. In the work the dependence of the E_em/E_0 ratio on the energy is given and experimental data are compared with calculations by the QGSJET model. The calculations have been carried out for the primary proton and iron nucleus. The average calculated meaning of the value of E_em/E_0 ratio (between the proton and iron nucleus) within experimental errors is in agreement with experimental data that doesnt contradict to the mixed mass composition of primary cosmic radiation.

astro-ph↗
arXiv2004

Cosmic Rays with Energy Above 10^{17} ev

The energy spectrum of primary cosmic rays with ultra high energies based on the Yakutsk EAS Array data is presented. For the largest events values of S600 and axis coordinates have been obtained using revised lateral distribution function. The affect of the arrival time distribution at several axis distance on estimated density for Yakutsk and AGASA is considered.

astro-ph↗
arXiv2004

Spectrum of cosmic rays with energy above $10^{17}$ eV

There are some discrepancies in the results on energy spectrum from Yakutsk, AGASA, and HiRes experiments. In this work differential energy spectrum of primary cosmic rays based on the Yakutsk EAS Array data is presented. For the largest events values of $S_{600}$ and axes coordinates have been obtained using revised lateral distribution function. Simulation of converter's response at large distances showed no considerable underestimation of particle density. Complex shape of spectrum in region of $\E > 10^{17}$ eV is confirmed. After adjustment of parameters and additional exposition at the Yakutsk array there are three events with energy $\E > 10^{20}$ eV.

astro-ph↗
arXiv2004

The compact mirrors with high pressure plasmas

At present, the GDT facility of the Budker Institute Novosibirsk, which is an axially symmetric magnetic mirror device of gas dynamic trap type, is being upgraded. The first stage of the upgrade is the Synthesised Hot Ion Plasmoid (SHIP) experiment. The experiments will be performed in a small mirror section that is installed at one side of the GDT. The magnetic field on axis will be in the range of 1-7 T and the mirror ratio will amount 1.2-1.4. The mirror is filled with background plasma streaming in from the central cell. Two neutral beam injectors perpendicularly inject a total current up to 120 equ. Amperes of hydrogen atoms with an energy of 25 keV as pulse with a duration of about 1 ms. Ionisation of the beams generates the high-energetic ion component with the high density and mean energy about 17 keV. The plasma bata ~ 0.8. This contribution explains the concept of the SHIP experiment and presents the results of SHIP simulation. The first experimental activity is also presented.

physics.plasm-ph↗
arXiv2004

Operator Method for Nonperturbative Calculation of the Thermodynamic Values in Quantum Statistics. Diatomic Molecular Gas

Operator method and cumulant expansion are used for nonperturbative calculation of the partition function and the free energy in quantum statistics. It is shown for Boltzmann diatomic molecular gas with some model intermolecular potentials that the zeroth order approximation of the proposed method interpolates the thermodynamic values with rather good accuracy in the entire range of both the Hamiltonian parameters and temperature. The systematic procedure for calculation of the corrections to the zeroth order approximation is also considered.

quant-ph↗
arXiv2004

The spectrum features of UHECRs below and surrounding GZK

The energy spectrum of UHECRs is discussed on the basis of the Yakutsk array database analysis. In the region E=0.1 to 30 EeV the showers are detected under trigger-500, while at energies above 30 EeV the whole acceptance area for trigger-1000 is used in order to utilize all the data available in the region of GZK cutoff.

astro-ph↗
arXiv2003

The energy spectrum of cosmic rays above 10^15 eV as derived from air Cherenkov light measurements in Yakutsk

The Yakutsk array observes the Cherenkov light emitted by UHECR in atmosphere. Recently, an autonomous subarray is added consisting of photomultipliers to measure the showers in the knee region. Our aim is to analyze the combined data set in order to derive the cosmic ray spectrum in the energy range as wide as possible using the same technique. The advantage of the air Cherenkov light measurement is the model independent estimation of the EAS primary energy using the total light flux emitted in the atmosphere. A set of the light lateral distributions observed in the extended energy range is presented also.

astro-ph↗
arXiv2002

The interplay of superconductivity and localization in Nd{2-x}Ce{x}CuO{4+δ} single crystal films

The influence of nonstoichiometric disorder on the in-plane resistivity and SC-transition has been investigated for Nd{2-x}Ce{x}CuO{4+δ} single crystal films (x=0.15 and 0.18). It is shown that with increasing of $δ$ the in-plane normal state resistivity increases (the mean free path diminishes) and SC-transition temperature decreases with essential broadening of the transition region. The observed evolution from homogeneous metallic (and superconducting) Nd{2-x}Ce{x}CuO{4+δ} system to inhomogeneous dielectric one is described as Anderson-type disorder-induced transition in a two-dimensional electron system.

cond-mat.supr-con↗
arXiv2000

Extended F_4-buildings and the Baby Monster

The Baby Monster group B acts naturally on a geometry E(B) with diagram c.F_4(t) for t=4 and the action of B on E(B) is flag-transitive. It possesses the following properties: (a) any two elements of type 1 are incident to at most one common element of type 2, and (b) three elements of type 1 are pairwise incident to common elements of type 2 iff they are incident to a common element of type 5. It is shown that E(B) is the only (non-necessary flag-transitive) c.F_4(t)-geometry, satisfying t=4, (a) and (b), thus obtaining the first characterization of B in terms of an incidence geometry, similar in vein to one known for classical groups acting on buildings. Further, it is shown that E(B) contains subgeometries E(^2E_6(2)) and E(Fi22) with diagrams c.F_4(2) and c.F_4(1). The stabilizers of these subgeometries induce on them flag-transitive actions of ^2E_6(2):2 and Fi22:2, respectively. Three further examples for t=2 with flag-transitive automorphism groups are constructed. A complete list of possibilities for the isomorphism type of the subgraph induced by the common neighbours of a pair of vertices at distance 2 in an arbitrary c.F_4(t) satisfying (a) and (b) is obtained.

math.GR↗
arXiv1999

Two-dimensional weak localization effects in high temperature superconductor Nd{2-x}Ce{x}CuO{4-d}

A systematic study of the resistivity and Hall effect in single crystal Nd{2-x}Ce{x}CuO{4-d} films (0.12 < x < 0.20) is presented, with special emphasis on the low-temperature dependence of the normal state conductance. Two-dimensional weak localization effects are found both in a normally conducting underdoped sample (x = 0.12) and in situ superconducting optimally doped (x = 0.15) or overdoped (x = 0.18) samples in a high magnetic field B > B{c2}. The phase coherence time and the effective thickness of a CuO{2} conducting layer {d} (~ 1.5 A) have been estimated by fitting 2D weak localization theory expressions to the magnetoresistivity data for magnetic fields perpendicular to the {ab} plane and in plane. Estimates of the parameter {d} ensure the condition of strong carrier confinement and justify a model consisting of almost decoupled 2D metallic sheets for the Nd{2-x}Ce{x}CuO{4-d} single crystal.

cond-mat.supr-con↗
arXiv1999

Azimuthal modulation of the event rate of cosmic ray extensive air showers by the geomagnetic field

The Earth's magnetic field effect on the azimuthal distribution of extensive air showers (EAS) of cosmic rays has been evaluated using a bulk of the Yakutsk array data. The uniform azimuthal distribution of the EAS event rate is rejected at the significance level 10^(-14). Amplitude of the first harmonics of observed distribution depends on zenith angle as A1=0.2*sin^2(theta) and is almost independent of the primary energy; the phase coincides with the magnetic meridian. Basing upon the value of measured effect, the correction factor has been derived for the particle density depending on a geomagnetic parameter of a shower.

astro-ph↗