Hasil untuk "gr-qc"

N. A. Lemos

We argue that the reasonings that underlie a recent comment by Gotay and Demaret [1, gr-qc/9605025] are defective. We maintain that, contrary to what they assert, our previous papers [2,3,4] are correct and indeed disprove their conjecture that quantum cosmological singularities are predetermined on the classical level by the choice of time.

L. Lusanna, R. Pietri

Guven, Murchadha

We continue our investigation of the configuration space of general relativity begun in I (gr-qc/9411009). Here we examine the Hamiltonian constraint when the spatial geometry is momentarily static (MS). We show that MS configurations satisfy both the positive quasi-local mass (QLM) theorem and its converse. We derive an analytical expression for the spatial metric in the neighborhood of a generic singularity. The corresponding curvature singularity shows up in the traceless component of the Ricci tensor. We show that if the energy density of matter is monotonically decreasing, the geometry cannot be singular. A supermetric on the configuration space which distinguishes between singular geometries and non-singular ones is constructed explicitly. Global necessary and sufficient criteria for the formation of trapped surfaces and singularities are framed in terms of inequalities which relate appropriate measures of the material energy content on a given support to a measure of its volume. The strength of these inequalities is gauged by exploiting the exactly solvable piece-wise constant density star as a template.

A. Mitra

In a recent preprint (astro-ph/9905144) Tereno has tried to find the physical 3-velocity (V) at the Event Horizon of a Kruskal Black Hole. This has been done in the backdrop of the recent work by Mitra (astro-ph/9904162) where it was shown that the radial geodesic of material particle, unphysically, becomes null at the Event Horizon. Although Tereno stops short of finding the precise value of V at r=2M, he concludes that V <1. It is pointed out with reference to Eq.(13) of Tereno's work that since his delta = (r -2M)/r tends to 0 as r tends to 2M, V indeed tends to 1. It appears that Tereno's conclusion is driven by his inability to conceive proper limiting value of fractions. Similarly, his idea that, the velocity addition formula of Sp. Theory of Relativity breaks down when both the velocities approach unity is due his same inability. In particular, our central result that Schwarschild BHs must have M=0 has been obtained independently from three different considerations (gr-qc/9810038, astro-ph/9904162, 163). And we also offer here the essential physical reason why the speed of free fall at the Event Horizon must be equal to the speed of light in coordinate system. Yet we are thankful to Tereno for making the first attempt to scientifically criticize our relevant work.

R. A. Vera

The theoretical properties of the black holes (BHs) and of the universe were derived from a unified relativistic theory based on a generalization of local relativity for nonlocal cases in gravitational fields and a quantized standing wave particle model that accounts for relativity, quantum mechanics and the gravitational tests (See gr-qc/9509014). They fix an isentropic and conservative steady state that is independent on an eventual universe expansion because matter also expands itself in the same proportion. The new black holes BHs resulting from linear properties of the model, after capturing enough radiation, would explode. Statistically, matter would evolve, indefinitely, in rather closed cycles between gas and BH states, and vice-versa. The expected astronomical objects and cosmic radiation backgrounds that are consistent with the observed facts. This leads to non conventional models for some celestial objects.

V. Mashkevich

This paper is a sequel to the series of papers [gr-qc/9409010, gr-qc/9505034, gr-qc/9603022, gr-qc/9609035, gr-qc/9609046, gr-qc/9704033, gr-qc/9704038]. Gravitational autolocalization of a body is considered. A self-consistent problem is solved: A quantum state of the center of mass of the body gives rise to a classical gravitational field, and the state, on the other hand, is an eigenstate in the field. We call a resulting solution gravilon. Gravilons are classified, and their properties are studied. Gravitational autolocalization is predominantly a macroscopic effect. The motion of a gravilon as a whole is classical.

V. Mashkevich

This paper is a sequel to the series of papers [gr-qc/9409010, gr-qc/9505034, gr-qc/9603022, gr-qc/9609035, gr-qc/9609046, gr-qc/9704033, gr-qc/9704038, gr-qc/9708014], being an immediate continuation and supplement to the last of them, where gravitational autolocalization of a body has been considered. A resulting solution, which describes a one-place location, has been called gravilon. Here it is shown that a gravilon is the only solution, i.e., that many-place gravitational autolocalization is unreal. This is closely related to nonreality of tunneling in the conditions under consideration.

E. R. Prakasan, Anil Sagar, V. L. Kalyane et al.

M. Korunur, A. Havare

This paper has been removed by arXiv administrators because of excessive overlap with gr-qc/0506062.

M. Salti

This paper has been removed by arXiv administrators because it plagiarizes gr-qc/0011027, "Viscous cosmologies in scalar-tensor theories for Kasner type metrics," by M. Cataldo, S. del Campo and P. Salgado; and gr-qc/0404108, "Energy and Momentum Densities Associated with Solutions Exhibiting Directional Type Singularities," by Ragab M. Gad.

A. Mitra

In a recent preprint, gr-qc/0511123, Dadhich has given a brief yet beautiful exposition on some of the research works by Prof. A.K. Raychaudhuri. Here Dadhich highlights the fact that the apparently ``self-evident'' assumption of occurrence of ``trapped surfaces'' may not be realized atleast in some specific cosmological models though no general proof for non-occurrence of trapped surfaces exists in the cosmological context. However, Dadhich added, without sufficient justification, that trapped surfaces should occur for collapse of isolated bodies. We point out that actually trapped surfaces do not occur even for collapse of spherically symmetric isolated bodies. Further unlike the cosmological case, for isolated bodies, an exact proof for generic non-occurrence of trapped surfaces is available. Thus for isolated bodies, the above referred apparently ``self-evident'' assumption fails much more acutely than in cosmology. Many recent astrophysical observations tend to corroborate the fact trapped surfaces do not occur for isolated bodies. Two recent specific papers (PRD) are cited to show that when radiative non-diispative collapse can prevent formation of trapped surfaces.

Jérôme Martin, P. Peter

In this web note, we reply to a recent paper, gr-qc/0404126, confirming a previous work of ours in which a cosmological bouncing phase was shown to have the ability of modifying the spectrum of primordial perturbations (PRD 68, 103517 2003), but challenging its physical conditions of validity. Explicitly, Ref. gr-qc/0404126, besides pretending our Taylor series expansion of the scale factor close to the bounce amounts to choosing a family of polynomial scale factors, also claims that the bounce affects the spectrum only if the mass scale of the scalar field driving the dynamics is of the order of the Planck mass. We show that these objections are either misleading or incorrect since the minimum size of the Universe a_0 (value of the scale factor at the bounce) is either not physically specified, as required in a closed Universe, or implicitly assumed to be the Planck mass. We calculate this mass and obtain that, unsurprisingly, for a reasonable value of a_0, i.e. much larger than the Planck length, the scalar field mass is smaller than the Planck mass.

B. McInnes

This paper has been superseded by gr-qc/0611101.

S. Aygun, M. Aygun, I. Tarhan

This paper has been removed by arXiv administrators because it plagiarizes gr-qc/0303009, hep-th/0405047, gr-qc/0602107, hep-th/0311050, gr-qc/0412120, gr-qc/0508005, and others. This paper has excessive overlap with the following papers also written by the authors or their collaborators: gr-qc/0607119, gr-qc/0607115, gr-qc/0606080, gr-qc/0607110, gr-qc/0607102, gr-qc/0510123, gr-qc/0607126, gr-qc/0602012, and others.

Andrzej Okołów, Jerzy Lewandowski

S. Mignemi

S. Aygun, M. Aygun, I. Tarhan

This paper has excessive overlap with the following papers also written by the authors or their collaborators: gr-qc/0607103, gr-qc/0607119, gr-qc/0607115, gr-qc/0607102, gr-qc/0602012, gr-qc/0702047, gr-qc/0607089, gr-qc/0510123, and others.

W. Rodrigues

This paper is a set of notes that we wrote concerning the first version of Emergent Gravity [gr-qc/0602022]. It is our version of an exercise that we proposed to some of our students. The idea was to find mathematical errors and inconsistencies on some recent articles published in scientific journals and in the arXiv, and we did.

Shih-Yuin Lin

We have shown the classical correspondence of Unruh effect in the classical relativistic electron theory in our previous work (gr-qc/0105051). Here we demonstrate the analogy between the classical relativistic electron theory and the classical Unruh-DeWitt type monopole detector theory. The field configuration generated by a uniformly accelerated detector is worked out. The classical correspondence of Unruh effect for scalar fields is shown by calculating the modified energy density for the scalar field around the detector. We conclude that a classical monopole detector cannot find any evidence about its acceleration unless it has a finite size.

Michael A. Ivanov

It was shown by the author (gr-qc/0207006) that screening the background of super-strong interacting gravitons creates Newtonian attraction if single gravitons are pairing and graviton pairs are destructed by collisions with a body. In such the model, Newton's constant is connected with Hubble's constant, for which the estimate is obtained: $94.576 km \cdot s^{-1} \cdot Mpc^{-1}.$ It is necessary to assume an atomic structure of any body to have the working model. Because of it, an existence of black holes contradicts to the equivalence principle in a frame of the model. For usual matter, the equivalence principle should be broken at distances $\sim 10^{-11} m,$ if the model is true.