167 research outputs found
Uncertainty Triggers Overreaction: Evidence from Corporate Takeovers
Behavioural finance models suggest that under uncertainty, investors overweight their private information and overreact to it. We test this theoretical prediction in an M&A framework. We find that under high information uncertainty, when investors are more likely to possess firm-specific information, acquiring firms generate highly positive and significant gains following the announcement of private stock and private cash acquisitions (positive news) while the market heavily punishes public stock (negative news) deals. On the other hand, under conditions of low information uncertainty, when investors do not possess private information, the market reaction is complete (i.e. zero abnormal returns) irrespective of the type of acquisition. Overall, we provide empirical evidence that shows that information uncertainty plays a significant role in explaining short-run acquirer abnormal returns
Bergmann-Thomson energy-momentum complex for solutions more general than the Kerr-Schild class
In a very well-known paper, Virbhadra's research group proved that the
Weinberg, Papapetrou, Landau and Lifshitz, and Einstein energy-momentum
complexes ``coincide'' for all metrics of Kerr-Schild class. A few years later,
Virbhadra clarified that this ``coincidence'' in fact holds for metrics more
general than the Kerr-Schild class. In the present paper, this study is
extended for the Bergmann-Thomson complex and it is proved that this complex
also ``coincides'' with those complexes for a more general than the Kerr-Schild
class metric.Comment: RevTex, 12 page
Tunnelling, Temperature and Taub-NUT Black Holes
We investigate quantum tunnelling methods for calculating black hole
temperature, specifically the null geodesic method of Parikh and Wilczek and
the Hamilton-Jacobi Ansatz method of Angheben et al. We consider application of
these methods to a broad class of spacetimes with event horizons, inlcuding
Rindler and non-static spacetimes such as Kerr-Newman and Taub-NUT. We obtain a
general form for the temperature of Taub-NUT-Ads black holes that is
commensurate with other methods. We examine the limitations of these methods
for extremal black holes, taking the extremal Reissner-Nordstrom spacetime as a
case in point.Comment: 22 pages, 3 figures; added references, fixed figures, added comments
to extremal section, added footnot
Quasinormal Modes in Noncommutative Schwarzschild black holes
We investigate the quasinormal modes of a massless scalar field in a
Schwarzschild black hole, which is deformed due to noncommutative corrections.
We present the deformed Schwarzschild black hole solution, which depends on the
noncommutative parameter , and we extract the master equation as a
Schr\"odinger-like equation, giving the explicit expression of the effective
potential which is modified due to the noncommutative corrections. We solve the
master equation numerically and we find that the noncommutative gravitational
corrections ``break" the stability of the scalar perturbations in the long time
evolution of the massless scalar field. The significance of these results is
twofold. Firstly, our results can be related to the detection of gravitational
waves by the near future gravitational wave detectors, such as LISA, which will
have a significantly increased accuracy. In particular, these observed
gravitational waves produced by binary strong gravitational systems have
oscillating modes which can provide valuable information. Secondly, our results
can serve as an additional tool to test the predictions of general relativity,
as well as to examine the possible detection of this kind of gravitational
corrections.Comment: 16 pages, 12 figure
On the energy of charged black holes in generalized dilaton-axion gravity
In this paper we calculate the energy distribution of some charged black
holes in generalized dilaton-axion gravity. The solutions correspond to charged
black holes arising in a Kalb-Ramond-dilaton background and some existing
non-rotating black hole solutions are recovered in special cases. We focus our
study to asymptotically flat and asymptotically non-flat types of solutions and
resort for this purpose to the M{\o}ller prescription. Various aspects of
energy are also analyzed.Comment: LaTe
Complex Effective Path: A Semi-Classical Probe of Quantum Effects
We discuss the notion of an effective, average, quantum mechanical path which
is a solution of the dynamical equations obtained by extremizing the quantum
effective action. Since the effective action can, in general, be complex, the
effective path will also, in general, be complex. The imaginary part of the
effective action is known to be related to the probability of particle creation
by an external source and hence we expect the imaginary part of the effective
path also to contain information about particle creation. We try to identify
such features using simple examples including that of effective path through
the black hole horizon leading to thermal radiation. Implications of this
approach are discussed.Comment: 20 pages; no figures; to appear in Phys.Rev.
Radiation via Tunneling from a de Sitter Cosmological Horizon
Hawking radiation can usefully be viewed as a semi-classical tunneling
process that originates at the black hole horizon. The same basic premise
should apply to de Sitter background radiation, with the cosmological horizon
of de Sitter space now playing the featured role. In fact, a recent work
[hep-th/0204107] has gone a long way to verifying the validity of this de
Sitter-tunneling picture. In the current paper, we extend these prior
considerations to arbitrary-dimensional de Sitter space, as well as
Schwarzschild-de Sitter spacetimes. It is shown that the tunneling formalism
naturally censors against any black hole with a mass in excess of the Nariai
value; thus enforcing a ``third law'' of Schwarzschild-de Sitter
thermodynamics. We also provide commentary on the dS/CFT correspondence in the
context of this tunneling framework.Comment: 19 pages, Latex; citation added; Eqs.(36,37) correcte
Quasi-normal modes, area spectra and multi-horizon spacetimes
We suggest an interpretation for the highly damped QNM frequencies of the
spherically symmetric multi-horizon spacetimes (Reissner-Nordstrom,
Schwarzschild-deSitter, Reissner-Nordstrom-deSitter) following Maggiore's
proposal about the link between the asymptotic QNM frequencies and the black
hole thermodynamics. We show that the behavior of the asymptotic frequencies is
easy to understand if one assumes that all of the horizons have the same
equispaced area spectra. The QNM analysis is then consistent with the choice of
the area spectra to be the one originally proposed for the black hole's horizon
by Bekenstein: A=8\pi n (in Planck units). The interpretation of the highly
damped QNM frequencies in the multi-horizon case is based on the similar
grounds as in the single horizon (Schwarzschild) case, but it has some new
features that are discussed in the paper.Comment: 8 pages, v2: no physics changed, some references added, few sentences
added in the discussion part
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