abstract

Coherent states play an important role in quantum physics. By studying the dynamical groups and recognizing their algebra relations, we can specify coherent states for these groups. In this paper, we will specify dynamical group of a charged particle in uniform and variable magnetic fields, then we obtain the coherent states for its corresponding problem.

abstract

Some principal problems of general relativity theory and attempts of their solution are discussed. The Poincaré gauge theory of gravity as natural generalization of Einsteinian gravitation theory is considered. The changes of gravitational interaction in the frame of this theory leading to the solution of principal problems of general relativity theory are analyzed.

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Black holes radiate not only the scalar particles but also Dirac particles. Extending Kerner and Mann’s work (Class. Quantum Grav. 25, 095014 (2008)) to the rotating and charged rotating black holes, we investigate the Hawking radiation of fermions for the Kerr black hole and Kerr–Newman black hole. The Hawking temperatures are recovered when the electromagnetic field effect and rotation effect are taken into account and are same as that computed by other methods.

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In this paper we apply the entropy function formalism to the two-dimen- sional black hole which come from the compactification of the heterotic string theory with the dilaton coupling function. We find the Bekenstein-Hawking entropy from the value of the entropy function at its saddle point. Also we consider higher derivative terms. After that we apply the entropy function formalism to the Jackiw–Teitelboim (JT) model where we consider the effect of string-loop to this model.

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We present an aid for importance sampling in Monte Carlo integration, which is of the general-purpose type in the sense that it in principle deals with any quadratically integrable integrand on a unit hyper-cube of arbitrary dimension. In contrast to most existing systems of this type, it does not ask for the integrand as an input variable, but provides a number of routines which can be plugged into a given Monte Carlo program in order to improve its efficiency “on the fly” while running. Due to the nature of its design, it can also be used for density estimation, i.e. , for the analysis of data points coming from an external source.

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We analyze stationary accretion of self gravitating gas onto a compact center within general-relativistic radiation hydrodynamics. Spherical symmetry and thin gas approximation are assumed. Numerical investigation shows that transonic flows exist for small redshifts and they cease to exist for high redshifts and high luminosities. There exist two branches of flows (subsonic or supersonic) that originate at a bifurcation point and that embrace the set of subsonic solutions. The morphology of the set of subsonic solutions is essentially independent of redshifts and flows that belong to their boundary provide estimates of the gas abundance of subsonic solutions. It appears that prescribed boundary data guarantee uniqueness only of the bifurcation point, and that the latter has maximal luminosity.

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The classical and quantum oscillator model on Lie-algebraically deformed nonrelativistic space-time is introduced and analyzed. The corresponding equations of motions are studied using mostly numerical methods. The time-dependent energy spectrum is presented as well.

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The prospects of probing anomalous \(Z\gamma \gamma \) and \(ZZ\gamma \) couplings by means of the subprocess \(\gamma q\rightarrow Zb\bar {(b)}\) in \(\gamma p\) collisions have been analyzed. The limits on the form factors \(h_{3}^{Z},\,h_{3}^{\gamma }\) and \(h_{4}^{Z},\,h_{4}^{\gamma }\) are obtained for three energy options of the \(\gamma p\) collisions. It is shown that the sensitivity can be reached \(\mathcal {O}\)\((10^{-4})\) if \(b\)-tagging is used.

abstract

The sticking probability of the muon to the \(\alpha \)-particle produced in the fusion process is the real bottleneck in the muonic three-body fusion. In this work, the stopping power of muonic helium ion in deuterium–tritium target has been obtained for different temperatures and densities as a function of velocity in plasma conditions. By taking all processes which can strip the muonic helium ion into account, the muon regeneration probability is computed. The calculated stopping power decreases with increasing temperature and density at any muonic helium ion velocity. The effective sticking decreases with increasing temperature and density. The results for the regeneration probability and the effective sticking are encouraging, and this investigation makes a contribution towards the goal of finding appropriate conditions which allow to achieve a positive energy balance in the muon catalyzed fusion \((\mu \)CF) process.

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The dependences of elliptic flows on transverse momentum for identified particles produced in nucleus–nucleus collisions at high energy are studied by using a multi source ideal gas model that describes the distribution of transverse momenta as a Rayleigh-like distribution. The experimental results of Au–Au collisions at \(\sqrt {s}=200A\) and 62.4\(A\) GeV and Cu–Cu collisions at \(\sqrt {s}=200A\) GeV, measured by the STAR and PHENIX collaborations, are well described by this model.

abstract

REACLIB is one of the most comprehensive and popular astrophysical reaction rate libraries. However, its experimentally obtained rates for light isotopes still rely mainly on the Caughlan and Fowler (1988) compilation and have never been updated despite the progress in many relevant nuclear astrophysics experiments. Moreover, due to fitting errors REACLIB is not reliable at temperatures lower than \(10^{7}\)K. In this work we establish the formalism for updating the obsolete Caughlan–Fowler experimental rates of REACLIB. Then we use the NACRE compilation and results from the LUNA experiments to update some important charged-particle induced rates of REACLIB focusing on the proton–proton chain. The updated rates (available also in digital form) can now be used in the low temperature regime (below \(10^{7}\)K) which was forbidden to the old version of REACLIB.

abstract

The influence of a few different Alfvén speed profiles \(V_{\rm A}(z)\) on the development of vertical oscillations of a curved coronal slab is investigated. Three particular cases are discussed: (a) \({dV_{\rm A}}\) / \({dz}\lt 0\), (b) \({dV_{\rm A}}\) / \({dz}=0\), (c) \({dV_{\rm A}}\) / \({dz}\gt 0\). These cases correspond respectively to the presence of wave tunnelling into the ambient medium above the slab (a), lack of any tunnelling (b), and tunnelling into the ambient medium below the slab (c). Two-dimensional ideal magnetohydrodynamic equations are solved by numerical means and the slab oscillations are triggered impulsively by an initial pulse in the vertical component of the momentum. We find that vertical oscillations exhibit time-signatures with characteristic wave period \(P\) and attenuation time \(\tau \). These parameters vary with \(V_{\rm A}(z)\). A smallest value of \(P\) is associated with the case of (c). A strongest attenuation (smallest \(\tau \)) of vertical oscillations takes place in the case of (a). A simple model of coronal loop oscillations leads to numerical results which are akin to the observational data of Wang and Solanki (2004).