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171.
R.N.P. Choudhury C. Rodríguez P. Bhattacharya R.S. Katiyar C. Rinaldi 《Journal of magnetism and magnetic materials》2007
Pb(Fe1/2Ta1/2)O3 (PFT) modified by rare-earth (La and Gd) ions has been synthesized in a single phase using a double-stage synthesis (i.e., Columbite) technique. Scanning electron micrographs (SEM) of the pellet samples have shown a significant change in their grain size and uniform distribution of Gd/La at the Fe-sites. The room temperature X-ray structural analysis shows that the reported cubic (or tetragonal) structure of PFT has been distorted to a monoclinic system on substitution of La/Gd at the Fe-site. Detailed studies of dielectric properties of the above compound on La/Gd substitution have shown strong dielectric dispersion at low frequency (i.e. relaxor behavior) with drastic change in transition temperature. Magnetic characterization shows that though the PFT sample displays an antiferromagnetic transition at ∼150 K, the rare-earth ions-substituted samples do not. Furthermore, temperature dependence of magnetization measurements shows that spin glass transition observed in PFT at low temperatures (5–20 K) does not exist in the La and Gd substituted PFT. Doping of Gd in PFT increases the sample magnetization, especially at low temperature. 相似文献
172.
Hawking radiation from the with a global monopole via Schwarzschild black hole gravitational anomaly
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This paper derives the Hawking flux from the Schwarzschild black hole with a global monopole by using Robinson and Wilczek's method. Adopting a dimensional reduction technique, it can describe the effective quantum field in the (3 + 1)-dimensional global monopole background by an infinite collection of the (1 + 1)-dimensional massless fields if neglecting the ingoing modes near the horizon, where the gravitational anomaly can be cancelled by the (1 + 1)- dimensional black body radiation at the Hawking temperature. 相似文献
173.
We have studied the Hawking radiation of the Kerr-Newman-Kasuya black hole via gauge and gravitational anomaly in the dragging coordinates. The fluxes of the electromagnetic current and the energy momentum tensor for each partial wave in two-dimensional field are obtained. 相似文献
174.
In this paper, Hawking radiation from the Kerr Newman de Sitter black hole is studied via gauge anomaly and gravitational anomaly. The obtained results of Hawking radiation from the event horizon and the cosmological horizon accord with those by other methods. 相似文献
175.
Viorel?BadescuEmail author Peter T.?LandsbergEmail author 《Foundations of Physics Letters》2005,18(3):205-226
Ideal Bose and Fermi systems are studied on the basis of a canonical ensemble, subject to the condition that their temperature is less than a given temperature Tmax. A single new parameter (the tau-parameter, τ) is needed to keep account of the new constraint. The parameter τ is shown to be the exponential of a pseudo-chemical potential that is linearly dependent on temperature. The inclusion of the τ- parameter leads to generalizations of usual thermodynamic quantities (internal energy, heat capacity and entropy) and various particular cases are discussed. The heat capacity of a Bose system can exhibit a maximum at a temperature less than the maximum temperature Tmax. The number of micro-states in the canonical ensemble is found to increase with τ. The heat capacity cV of a Fermi system of non-interacting spins exhibits a Schottky anomaly. The peak depends on τ, and for some cases cV/k can significantly exceed unity. The influence of τ on the entropy of the Fermi system and on the number of micro-states in the canonical ensemble is significant but not spectacular. 相似文献
176.
George?Tsouproslandaughost@hotmail.com" title="gts@pku.edu.cn landaughost@hotmail.com" itemprop="email" data-track="click" data-track-action="Email author" data-track-label="">Email author 《General Relativity and Gravitation》2005,37(2):399-406
The trace anomaly for free propagation in the context of a conformally invariant scalar field theory defined on a curved manifold of positive constant curvature with boundary is evaluated through use of an asymptotic heat kernel expansion. In addition to their direct physical significance the results are also of relevance to the holographic principle and to Quantum Cosmology. 相似文献
177.
Y.O. Ciftci X.F. Wang P. Vasilopoulos 《Physica E: Low-dimensional Systems and Nanostructures》2005,30(1-2):74-80
We study spin transport of holes through microstructures modulated periodically by diluted magnetic semiconductor (DMS) sections, stubless or stubbed. The stubs are symmetric or asymmetric and the magnetizations of consecutive DMS sections are parallel or antiparallel. The transmission coefficients of holes with spin up (T+) or down (T-) are drastically different since the spins feel different potential profiles in the DMS sections. As a result, nearly square-wave patterns, or wide plateaus and oscillations, can be obtained for the transmission and the spin polarization as functions of the incident energy or of various parameters of the periodically repeated unit. Results for simple and composite units with and without deviations from perfect periodicity are reported. Some of the structures considered exhibit a strong spin-filtering behavior. 相似文献
178.
This work proposes an explanation of the Pioneer anomaly, the unmodelled and as yet unexplained blueshift detected in the microwave signal of the Pioneer 10 and other spaceships by Anderson et al. in 1998. What they observed is similar to the effect that would have either (i) an anomalous acceleration aP the ship towards the Sun, or (ii) an acceleration of the clocks at=aP/c. The second alternative is investigated here, with a phenomenological model in which the anomaly is an effect of the background gravitational potential (t) that pervades all the universe and is increasing because of the expansion. It is shown that 2at=d /dt=d2clocks/dt2, evaluated at present time t0, where t and clocks are the coordinate time and the time measured by the atomic clocks, respectively. The result of a simple estimate gives the value at 1.8× 10–18 s–1, while Anderson et al. suggested at=(2.9±0.4) × 10–18 s–1 on the basis of their observations. The calculation are performed near the Newtonian limit but in the frame of general relativity. 相似文献
179.
Hawking radiation from cosmological horizon and event horizon of the Reissner-Nordström de Sitter black hole with a global monopole is studied via a new method that was propounded by Robinson and Wilzek and elaborated by Banerjee and Kulkarni. The results show that the gauge current and energy-momentum tensor fluxes, which required keeping gauge covariance and general coordinate invariance at the quantum level in the effective field theory, are exactly equivalent to those of Hawking radiation from the event horizon and the cosmological horizon,
respectively. 相似文献
180.
HE Han-Xin 《理论物理通讯》2001,36(3):285-286
By computing the axial-vector current operator equation,
we find the anomalous axial-vector curl equation besides the well-known
anomalous axial-vector divergence equation (the Adler-Bell-Jackiw anomaly)
and discuss its implication. 相似文献