共查询到20条相似文献,搜索用时 31 毫秒
1.
V. V. Skobelev 《Journal of Experimental and Theoretical Physics》2010,110(2):211-219
The resonance effect of emission of axions by a hydrogen-like atom in an ultrastrong magnetic field B ≫ B
0 = m
2/e = 4.41 × 1013 Gs, which is induced by polarization of electron-positron vacuum, is considered. The emission probability and the radiation
intensity are on the order of (B/B
0) × 10−12 of electromagnetic radiation characteristics, which exceeds the conventional ratio by many orders of magnitude. It is shown
that, at the temperature of early Universe ≲(Zα)2
m, the contribution from the resonance mechanism prevails. However, the relation between the concentrations of relic photons
and axions cannot explain the origin of cold dark matter. The axion energy density in “our epoch” is 10−4(B/B
0) eV/cm3. 相似文献
2.
V. V. Skobelev 《Journal of Experimental and Theoretical Physics》2007,105(5):982-987
It was shown that the contribution of diagrams with electron-positron vacuum excitation in a strong magnetic field B ? B 0 = m 2/e = 4.41 × 1013 G in the Compton mechanism of axion production γe → ae at temperatures on the order of the axion mass exceeds the contribution of the “simple” Compton diagram and the contribution of the neutrino production γe → (ν\(\bar \nu \))e to the radiation power by many orders of magnitude. The conclusion is made on the probable axionic nature of the cold hidden mass of the Universe. 相似文献
3.
V. V. Skobelev 《Russian Physics Journal》2009,52(7):704-714
The probability and intensity of neutrino radiation of a hydrogen-like atom in the strong magnetic field B >> Z
2α2
B
0, α = e
2 = 1/137, B
0 = m
2/e = 4.41⋅1013 G are determined. The temperature dependence of the intensity of an atom ensemble is analyzed. 相似文献
4.
V. V. Skobelev 《Journal of Experimental and Theoretical Physics》1999,89(1):13-17
The axion vertex aγγγ, the probability of three-photon axion decay in an external magnetic field, and the cross section of the crossing process
aγ→2γ, which CP invariance forbids in vacuum, are calculated for the first time. It is shown that in superstrong magnetic fields B≫F
0=m
2/|e|=4.41·1013
G the probability of three-photon decay is greater than the probability of two-photon decay. The astrophysical aspects of the
questions examined are discussed.
Zh. éksp. Teor. Fiz. 116, 26–34 (July 1999) 相似文献
5.
V. V. Skobelev 《Russian Physics Journal》2010,53(2):198-208
The probability and intensity of hydrogen-like atom emission in strong magnetic field В >> Z
2α2
B
0, α = e
2/cħ = 1/137, and B
0 = m
2
c
3 /eħ = 4.41⋅1013
G is calculated. The role of electron-positron vacuum polarization is discussed. 相似文献
6.
V. V. Skobelev 《Physics of Atomic Nuclei》2011,74(1):110-114
By using the polarization density matrix for a neutron in a magnetic field, the axion luminosity of magnetic neutron stars
that is associated with the flip of the anomalous magnetic moment of degenerate nonrelativistic neutrons is calculated. It
is shown that, at values of the magnetic-field induction in the region B ≳ 1018 G, this mechanism of axion emission is dominant in “young” neutron stars of temperature about a few tens of MeV units. At
B ∼ 1017 G, it is one of the basic mechanisms. The Fermi energy of a degenerate neutron gas in a magnetic field is found, and it is
shown that there is no such mechanism of axion emission in the degenerate case. 相似文献
7.
V. V. Skobelev 《Journal of Experimental and Theoretical Physics》1998,86(5):850-853
The dominant one-loop electron contribution to the mass operator of an axion in a crossed field in the asymptotic limits of
the parameters q
2/m
e
2
and
is calculated. The corresponding electromagnetic mass of the axion is compared with the quantum-chromodynamic mass due to
mixing with π. Expressions are derived for the probability of pair creation a→e
+
e
−, and the fundamental conclusion is reached that refractive effects are present in the propagation of an axion in an external
electromagnetic field.
Zh. éksp. Teor. Fiz. 113, 1558–1565 (May 1998) 相似文献
8.
The retardation of the recombination of electrons and holes in semiconductors in an applied uniform magnetic field has been
predicted. It has been shown that the recombination time in germanium in the temperature range of T = 1–10 K at charge carrier densities of n
e
= 1010−1014 cm−3 in magnetic fields of B = 3 × 102−3 × 104 G can be more than two orders of magnitude larger than that at zero magnetic field. This means that, after creation of nonequilibrium
charge carriers by their injection at the p-n junction owing to some radiation sources or fast electron irradiation, the semiconductor retains its conductivity for a much
longer time at nonzero applied magnetic field. The effect under study can be used, for example, to detect radiation sources. 相似文献
9.
The polarization operator of an axion in a degenerate gas of electrons occupying the ground-state Landau level in superstrong
magnetic fields H≫H
0=m
e
2
c
3/eℏ=4.41×1013 G is investigated in a model with a tree-level axion-electron coupling. It is shown that a dynamic axion mass, which can
fall within the allowed range of values 10−5 eV≲m
a≲102 eV, is generated under the conditions of strongly magnetized neutron stars. As a result, the dispersion relation for axions
is appreciably different from that in a vacuum.
Zh. éksp. Teor. Fiz. 115, 3–11 (January 1999) 相似文献
10.
V. V. Skobelev 《Journal of Experimental and Theoretical Physics》2001,93(4):685-694
Photogeneration of neutrinos and axions at nuclei, $\gamma (Ze) \uparrow \gamma (\nu \bar \nu ),\gamma a$ , and inelastic photon-photon scattering, $\gamma \gamma \uparrow \gamma (\nu \bar \nu ),\gamma a$ , are considered in the 2D covariant theory being developed for calculating matrix elements of Feynman diagrams in a strong magnetic field. Since the matrix elements of four-pole diagrams are linear functions of the magnetic induction B, the contribution of the radiative photogeneration of neutrinos at nuclei to the luminosity of magnetic neutron stars at early stages of their evolution may compete with URCA processes for values of B ~ (103–104)B 0 (B 0 = m 2 e /|e| = 4.41 × 1013 G). The upper estimate of the axion mass obtained from the condition of dominance of the neutrino luminosity over the axion luminosity for the proposed values of temperature and magnetic induction is in accord with other independent results. 相似文献
11.
D.N. McIlroy S.-D. Hwang K. Yang N. Remmes P.A. Dowben A.A. Ahmad N.J. Ianno J.Z. Li J.Y. Lin H.X. Jiang 《Applied Physics A: Materials Science & Processing》1998,67(3):335-342
5 C) alloy thin films grown by plasma-enhanced chemical vapor deposition have been examined. The Ni-doped boron–carbon alloys
were grown using closo-1,2-dicarbadodecaborane (C2B10H12) as the boron–carbon source compound and nickelocene(Ni(C5H5)2) as the nickel source. The phosphorus-doped alloys were grown using the single-source compound: dimeric chloro-phospha(III)-carborane
([C2B10H10PCl]2). Nickel doping increased the conductivity, relative to undoped B5C, by six orders of magnitude from 10-9 to 10-3 (Ω cm)-1 and transformed the material from a p-type semiconductor to an n-type. Phosphorus doping decreased the conductivity, relative
to undoped B5C, by two orders of magnitude and increased the band gap from 0.9 eV for the undoped material to 2.6 eV. Infrared absorption
spectra of the nickel- and phosphorus-doped B5C alloys were relatively unchanged from those of undoped B5C. X-ray diffraction suggests that the phosphorus-doped material may be a different polytype from the Ni-doped and undoped
B5C alloys.
Received: 23 April 1997/Accepted: 3 November 1997 相似文献
12.
V. V. Skobelev 《Journal of Experimental and Theoretical Physics》1997,85(1):13-16
We consider axion formation processes in the synchrotron (e
−→e
−
a) and annihilation (e
−
e
+→a) channels in a constant crossed field F
μν
Fμν=Fμν*F
μν
=0, which approximates constant fields of other configurations in the ultrarelativistic asymptotic limit. The probability
and intensity of axion emission are obtained, and we analyze the energy and field asymptotics. A comparison with the characteristic
neutrino channel
yields the constraints on the axion mass and the energy scale for Peccei-Quinn symmetry breaking. Possible astrophysical
applications are discussed.
Zh. éksp. Teor. Fiz. 112, 25–31 (July 1997) 相似文献
13.
L. I. Koroleva D. M. Zashchirinski T. M. Khapaeva L. I. Gurski N. A. Kalanda V. M. Trukhan R. Szymczak B. Krzumanska 《Physics of the Solid State》2008,50(12):2298-2302
This paper reports on a study of the effect of oxygen deficiency on the magnetic and electrical properties of the La1 − x
Sr
x
MnO3 − δ manganites (x = 0, 0.2, 0.4; δ = 0, 0.13, 0.2). In compositions with x = 0 and δ = 0.13 and 0.2, the temperature dependence of the magnetization M (T) can be approximated by the Langevin function with the moment of superparamagnetic clusters μ = 77μB (δ = 0.13) and 86μB (δ = 0.2) at temperatures of 25 K ≤ T ≤ 250 K, with the exception of a small temperature range near 132 K in which a maximum characteristic of the LaMnO3 antiferromagnet is seen. These compositions, as well as Sr-doped compositions with δ ≠ 0, reveal a difference between the
magnetizations of the sample cooled in a weak magnetic field and in zero field. At T = 6 K in a magnetic field of 16 kOe, the compositions with x = 0.2 and 0.4, δ = 0.13 possess a magnetic moment per formula unit lower than that with δ = 0, as well as reveal an anomalous
relation between the Curie temperature T
C and the Curie paramagnetic point gJ, namely, T
C > gJ. The magnetization of compositions with x = 0.2 and 0.4, δ = 0.2 follows the Langevin function with μ = 40μB and 130μB, respectively. The electrical resistivity of samples with x = 0.4 and δ = 0.13 and 0.2 is one to two orders of magnitude larger than that of the composition with x = 0.4, δ = 0, which evidences partial or complete compensation of acceptor defects (Sr2+ ions) by donor defects (doubly charged O2− vacancies). The above properties of oxygen-deficient compositions suggest that they contain an insulating ferro-antiferromagnetic
magnetically double-phase state. The magnetoresistance and volume magnetostriction in samples with x = 0.4 and δ = 0, 0.13, and 0.2 are small; indeed, in a magnetic field of 8 kOe, they do not exceed 1.4% and 6 × 10−6, respectively. On this basis, it is concluded that the unbalanced doubly charged donors (O vacancies) are in the state with
antiparallel spins and, thus, do not initiate the formation of ferron-type ferromagnetic clusters. The significance of both
compensated and unbalanced doubly charged donors consists in that they give rise to the formation of fractured Mn-O-Mn bonds,
which bring about lowering of the magnetic moment per formula unit in compositions with x = 0.2 and 0.4 and δ = 0.13 and the transition to superparamagnetism in compositions with x = 0.2 and 0.4, δ = 0.2.
Original Russian Text ? L.I. Koroleva, D.M. Zashchirinskiĭ, T.M. Khapaeva, L.I. Gurskiĭ, N.A. Kalanda, V.M. Trukhan, R. Szymczak,
B. Krzumanska, 2008, published in Fizika Tverdogo Tela, 2008, Vol. 50, No. 12, pp. 2201–2205. 相似文献
14.
《The European Physical Journal C - Particles and Fields》2008,54(1):61-72
Results of background measurements with a prototype of the Borexino detector were used to search for 478 keV solar axions
emitted in the M1-transitions of 7Li*. The Compton conversion of axion to a photon A+e→e+γ, axioelectric effect A+e+Z→e+Z, decay of axion in two photons A→2γ and
Primakoff conversion on nuclei A+Z→γ+Z are considered. The upper limit on constants of interaction of axion with electrons,
photons and nucleons – gAegAN≤(1.0–2.4)×10-10 at mA≤450 keV and gAγgAN≤5×10-9 GeV-1 at mA≤10 keV are obtained (90%c.l.). For heavy axions with mass at 100<mA<400 keV the limits gAe<(0.7–2.0)×10-8 and gAγ<10-9–10-8 are obtained in assumption that gAN depends on mA as for KSVZ axion model. These limits are stronger than obtained in previous laboratory-based experiments using nuclear reactor
and artificial radioactive sources.
PACS 14.80.Mz; 29.40.Mc; 26.65.+t 相似文献
15.
In-Sang YangM.V Klein S Bud'koP.C Canfield 《Journal of Physics and Chemistry of Solids》2002,63(12):2195-2200
The nickel borocarbides RNi2B2C, R=Y or Lu, have a superconducting Tc of 15-16 K and exhibit properties consistent with an anisotropic s-wave gap. We briefly review their properties. Electronic Raman scattering results are presented on YNi2B2C containing 11B or 10B. In A1g and B1g Raman symmetries, there is no shift in the position of the ‘2Δ’ peak with B-isotope. There is a distinct negative shift, however, in B2g symmetry. This is interpreted as a negative isotope shift for the gap Δ on that portion of the Fermi surface where the magnitude of the B2g Raman vertex is large. 相似文献
16.
Zhi-Gang Wang 《The European Physical Journal C - Particles and Fields》2008,56(2):181-187
In this article, we calculate the strong coupling constants gBs0Bsη and gBs1B*sη with the light-cone QCD sum rules. Then we take into account the small η–π0 transition matrix according to Dashen’s theorem, and we obtain the small decay widths for the isospin violation processes
Bs0→Bsη→Bsπ0 and Bs1→Bs
*η→Bs
*π0. We can search the strange-bottomed (0+,1+) mesons Bs0 and Bs1 in the invariant Bsπ0 and B*
sπ0 mass distributions, respectively.
PACS 12.38.Lg; 13.25.Hw; 14.40.Nd 相似文献
17.
From the time of CMB decoupling onwards we investigate cosmological evolution subject to a strongly interacting SU(2) gauge
theory of Yang–Mills scale, Λ ∼ 10-4 eV (masquerading as the U(1)Y factor of the SM at present). The viability of this postulate is discussed in view of cosmological and (astro-) particle
physics bounds. The gauge theory is coupled to a spatially homogeneous and ultralight (Planck-scale) axion field. As first
pointed out by Frieman et al., such an axion is a viable candidate for quintessence, i.e. dynamical dark energy, being associated
with today’s cosmological acceleration. A prediction of an upper limit for Δtmγ=0, the duration of the epoch stretching from the present to the point where the photon starts to be Meissner massive, is obtained:
Δtmγ=0∼2.2 billion years. 相似文献
18.
V. I. Vysotskii M. V. Vysotskyy S. V. Adamenko 《Journal of Experimental and Theoretical Physics》2012,114(2):243-252
We consider prerequisites and investigate some optimal methods for the formation of a correlated coherent state of interacting
particles in nonstationary systems. We study the influence of the degree of particle correlation on the probability of their
passage through the Coulomb barrier for the realization of nuclear reactions at low energies. For such processes, the tunneling
probability and, accordingly, the probability of nuclear reactions can grow by many orders of magnitude (in particular, the
barrier transparency increases from D
r = 0 ≈ 10−42 for an uncorrelated state to D
|r| = 0.98 ≈ 0.1 at a correlation coefficient |r| ≈ 0.98). The formation of a correlated particle state is considered in detail for different types of monotonic decrease
in the frequency of a harmonic oscillator with the particle located in its parabolic field. For the first time, we have considered
the peculiarities and investigated the efficiency of the creation of a correlated state under a periodic action on a harmonic
oscillator. This method is shown to lead to rapid formation of a strongly correlated particle state that provides an almost
complete clearing of the potential barrier even for a narrow range of oscillator frequency variations. 相似文献
19.
A. V. Derbin A. I. Egorov I. A. Mitropol’skii V. N. Muratova S. V. Bakhlanov L. M. Tukhkonen 《JETP Letters》1997,65(8):605-610
A method of searching for the invisible axion emitted in M transitions of isomeric nuclei is proposed. It is determined experimentally
that the probability of emission of an axion in the M1 transition in 125m
Te is ⩽1.3⋅10−5 (90% confidence level).
Pis’ma Zh. éksp. Teor. Fiz. 65, No. 8, 576–580 (25 April 1997) 相似文献
20.
M. Beneke G. Buchalla M. Neubert C. T. Sachrajda 《The European Physical Journal C - Particles and Fields》2009,61(3):439-449
The integrated branching fraction of the process B→X
s
l
+
l
− is dominated by resonance background from narrow charmonium states, such as B→X
s
ψ→X
s
l
+
l
−, which exceeds the non-resonant charm-loop contribution by two orders of magnitude. The origin of this fact is discussed
in view of the general expectation of quark–hadron duality. The situation in B→X
s
l
+
l
− is contrasted with charm-penguin amplitudes in two-body hadronic B decays of the type B→π
π, for which it is demonstrated that resonance effects and the potentially non-perturbative
threshold region do not invalidate the standard picture of QCD factorization. This holds irrespective of whether the charm
quark is treated as a light or a heavy quark. 相似文献