共查询到20条相似文献,搜索用时 15 毫秒
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《Physics letters. [Part B]》1999,459(4):468-472
We propose a new generalisation of general relativity which incorporates a variation in both the speed of light in vacuum (c) and the gravitational constant (G) and which is both covariant and Lorentz invariant. We solve the generalised Einstein equations for Friedmann universes and show that arbitrary time-variations of c and G never lead to a solution to the flatness, horizon or Λ problems for a theory satisfying the strong energy condition. In order to do so, one needs to construct a theory which does not reduce to the standard one for any choice of time, length and energy units. This can be achieved by breaking a number of invariance principles such as covariance and Lorentz invariance. 相似文献
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《Physics letters. [Part B]》1986,168(3):295
It is shown that a mechanism of coherent enhancement of the cross section of the neutrino scattering in a periodic structure, suggested by Weber could be excluded by the present neutron scattering experiments. 相似文献
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Comments on “Translation-invariant bipolarons and the problem of high-temperature superconductivity”
We comment on the recent results of Refs. [1], [2] on the bipolaron problem derived using an approximation of Gross–Tulub. It is proved that, contrary to the claim made in Refs. [1], [2], the bipolaron ground-state energy calculated there in the strong-coupling approximation has not been shown to constitute a variational upper bound. 相似文献
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Gil Jannes 《Foundations of Physics》2009,39(4):397-406
I discuss some problems related to extreme mathematical realism, focusing on a recently proposed “shut-up-and-calculate” approach
to physics (Tegmark in Found. Phys. 38:101, 2008; New Sci., September 15th, 2007). I offer arguments for a moderate alternative, the essence of which lies in the acceptance that mathematics is (at least
in part) a human construction, and discuss concrete consequences of this—at first sight purely philosophical—difference in
point of view. 相似文献
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We assess the validity of “microscopic” approaches of glass-forming liquids based on the sole knowledge of the static pair
density correlations. To do so, we apply them to a benchmark provided by two liquid models that share very similar static
pair density correlation functions while displaying distinct temperature evolutions of their relaxation times. We find that
the approaches are unsuccessful in describing the difference in the dynamical behavior of the two models. Our study is not
exhaustive, and we have not tested the effect of adding corrections by including, for instance, three-body density correlations.
Yet, our results appear strong enough to challenge the claim that the slowdown of relaxation in glass-forming liquids, for
which it is well established that the changes of the static structure factor with temperature are small, can be explained
by “microscopic” approaches only requiring the static pair density correlations as nontrivial input. 相似文献
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Invariance of the one-dimensional lattice Boltzmann model is proposed together with its rigorous theoretical background. It is demonstrated that the symmetry inherent in Navier-Stokes equations is not really recovered in the one-dimensional lattice Boltzmann equation (LBE), especially for shock calculation. Symmetry breaking may be the inherent cause for the non-physical oscillations in the vicinity of the shock for LBE calculation. 相似文献
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Growth of the V4 centers during and after pulsed electron irradiation of KBr was measured between 77K and 200K. It is found that the growth during pulsed irradiation is clearly different from that due to the thermal motion of the H centers. Critical discussions on the mechanism of the interstitial interaction in the primary step of the Frenkel-pair creation were made. 相似文献
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《Physica A》1995,216(3):249-254
Cross effects arising in a binary mixture of rarefied gases confined between two infinite plates are studied. The Onsager reciprocity relations for these phenomena have been derived applying general properties of the Boltzmann equation and the boundary conditions for the distribution function. Phenomena taking place only when the upper and lower plates are different have been distinguished. It has been pointed out that the cross effects considered by Vysotsky and Roldughin [Physica A 209 (1994) 25] are not a consequence of the surface accommodation difference of the plates as they assert. 相似文献
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A numerical simulation has been performed, indicating that the statement on the detection of water dimer absorption by V.I.
Serdyukov et al. in Pis’ma Zh. Eksp. Teor. Fiz. 89, 12 (2009) [JETP Lett. 89, 10 (2009)] had been premature. Most of the revealed induced absorption can be attributed to water monomers. 相似文献
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Shigeru Takata 《Journal of statistical physics》2010,139(3):538-539
This is a reply to the comments by Sharipov on the papers published in J. Stat. Phys. 136:751 (2009) and in J. Stat. Phys. 136:945 (2009). The present reply will show that the comments do not apply to the papers. 相似文献
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《Physics letters. A》2002,296(6):307-311
Discussion of the differences between the trajectory representation of Floyd and that of Bouda and Djama [Phys. Lett. A 285 (2001) 27] renders insight: while Floyd's trajectories are related to group velocities, Bouda and Djama's are not. Bouda and Djama's reasons for these differences are also addressed. 相似文献
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《Physics letters. A》1988,131(3):171-173
It is shown that two recently published counterexamples to the cosmological “no hair” conjecture are merely coordinate transforms of the de Sitter spacetime. 相似文献