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81.
Alexander?B.?Balakin Winfried?ZimdahlEmail author 《General Relativity and Gravitation》2005,37(10):1731-1751
The material tensor of linear response in electrodynamics is constructed out of products of two symmetric second rank tensor
fields which in the approximation of geometrical optics and for uniaxial symmetry reduce to “optical” metrics, describing
the phenomenon of birefringence. This representation is interpreted in the context of an underlying internal geometrical structure
according to which the symmetric tensor fields are vectorial elements of an associated two-dimensional space. 相似文献
82.
Winfried Kohnen 《Monatshefte für Mathematik》2004,143(2):163-167
We point out that the formalism of the trace map and reduction modulo p can be used to give a short proof for the fact first proved by Ogg that is not a Weierstrass point on X0(pM) where p is a prime not dividing M and the genus of X0(M) is zero. 相似文献
83.
We argue that the recently introduced statefinder parameters (Sahni et al., JETP Lett. 77, 201 (2003)), that include the third derivative of the cosmic scale factor, are useful tools to characterize interacting quintessence models. We specify the statefinder parameters for two classes of models that solve, or at least alleviate, the coincidence problem. 相似文献
84.
We calculate the net-baryon rapidity distribution in Au+Au collisions at the Relativistic Heavy Ion Collider (RHIC) in the framework of the parton cascade model (PCM). Parton rescattering and fragmentation leads to a substantial increase in the net-baryon density at midrapidity over the density produced by initial primary parton-parton scatterings. The PCM is able to describe the measured net-baryon density at RHIC. 相似文献
85.
We show that with the help of a suitable coupling between dark energy and cold dark matter it is possible to reproduce any scaling solution
X
M
a
, where
X
and
M
are the densities of dark energy and dark matter, respectively. We demonstrate how the case = 1 alleviates the coincidence problem. Future observations of supernovae at high redshift as well as quasar pairs which are planned to discriminate between different cosmological models will also provide direct constraints on the coupling between dark matter and dark energy. 相似文献
86.
87.
We investigate the minimal number of generators and the depth of divisorial ideals over normal semigroup rings. Such ideals are defined by the inhomogeneous systems of linear inequalities associated with the support hyperplanes of the semigroup. The main result is that for every bound C there exist, up to isomorphism, only finitely many divisorial ideals I such that (I)C. It follows that there exist only finitely many Cohen–Macaulay divisor classes. Moreover, we determine the minimal depth of all divisorial ideals and the behaviour of and depth in arithmetic progressions in the divisor class group.The results are generalized to more general systems of linear inequalities whose homogeneous versions define the semigroup in a not necessarily irredundant way. The ideals arising this way can also be considered as defined by the nonnegative solutions of an inhomogeneous system of linear diophantine equations.We also give a more ring-theoretic approach to the theorem on minimal number of generators of divisorial ideals: it turns out to be a special instance of a theorem on the growth of multigraded Hilbert functions. 相似文献
88.
We reveal unifying thermodynamic aspects of so different phenomena as the cosmological electron-positron annihilation, the evaporation of primordial black holes with a narrow mass range, and the "deflationary" transition from an initial de Sitter phase to a subsequent standard Friedmann–Lemaître–Robertson–Walker (FLRW) behavior. 相似文献
89.
Winfried Kohnen Jyoti Sengupta 《Proceedings of the American Mathematical Society》2000,128(6):1641-1646
We shall give a certain nonvanishing result for the symmetric square -function of an elliptic cuspidal Hecke eigenform w.r.t. the full modular group inside the critical strip.
90.
In 1876, H. Brocard posed the problem of finding all integral solutions to n! + 1 = m2. In 1913, unaware of Brocard's query, S. Ramanujan gave the problem in the form, The number 1 + n! is a perfect square for the values 4, 5, 7 of n. Find other values. We report on calculations up to n = 109 and briefly discuss a related problem. 相似文献