scholarly journals On a Possibly Pure Set-Theoretic Contribution to Black Hole Entropy

2019 ◽  
Vol 25 (2) ◽  
pp. 327-340 ◽  
Author(s):  
Gábor Etesi

Abstract Continuity as appears to us immediately by intuition (in the flow of time and in motion) differs from its current formalization, the arithmetical continuum or equivalently the set of real numbers used in modern mathematical analysis. Motivated by the known mathematical and physical problems arising from this formalization of the continuum, our aim in this paper is twofold. Firstly, by interpreting Chaitin’s variant of Gödel’s first incompleteness theorem as an inherent uncertainty or fuzziness of the arithmetical continuum, a formal set-theoretic entropy is assigned to the arithmetical continuum. Secondly, by analyzing Noether’s theorem on symmetries and conserved quantities, we argue that whenever the four dimensional space-time continuum containing a single, stationary, asymptotically flat black hole is modeled by the arithmetical continuum in the mathematical formulation of general relativity, the hidden set-theoretic entropy of this latter structure reveals itself as the entropy of the black hole (proportional to the area of its “instantaneous” event horizon), indicating that this apparently physical quantity might have a pure set-theoretic origin, too.

2009 ◽  
Vol 18 (04) ◽  
pp. 599-611 ◽  
Author(s):  
ALFRED MOLINA ◽  
NARESH DADHICH

By considering the product of the usual four-dimensional space–time with two dimensional space of constant curvature, an interesting black hole solution has recently been found for Einstein–Gauss–Bonnet gravity. It turns out that this as well as all others could easily be made to radiate Vaidya null dust. However, there exists no Kerr analog in this setting. To get the physical feel of the four-dimensional black hole space–times, we study asymptotic behavior of stresses at the two ends, r → 0 and r → ∞.


2019 ◽  
Vol 97 (12) ◽  
pp. 1317-1322
Author(s):  
Abeer Al-Modlej ◽  
Salwa Alsaleh ◽  
Hassan Alshal ◽  
Ahmed Farag Ali

Virtual black holes in noncommutative space–time are investigated using coordinate coherent state formalism such that the event horizon of a black hole is manipulated by smearing it with a Gaussian of width [Formula: see text], where θ is the noncommutativity parameter. Proton lifetime, the main associated phenomenology of the noncommutative virtual black holes, has been studied, first in four-dimensional space–time and then generalized to D dimensions. The lifetime depends on θ and the number of space–time dimensions such that it emphasizes on the measurement of proton lifetime as a potential probe for the microstructure of space–time.


KronoScope ◽  
2013 ◽  
Vol 13 (1) ◽  
pp. 67-84 ◽  
Author(s):  
Pierre Martinetti

Abstract We discuss the emergence of time in quantum gravity and ask whether time is always “something that flows.” We first recall that this is indeed the case in both relativity and quantum mechanics, although in very different manners: time flows geometrically in relativity (i.e., as a flow of proper time in the four dimensional space-time), time flows abstractly in quantum mechanics (i.e., as a flow in the space of observables of the system). We then ask the same question in quantum gravity in the light of the thermal time hypothesis of Connes and Rovelli. The latter proposes to answer the question of time in quantum gravity (or at least one of its many aspects) by postulating that time is a state-dependent notion. This means that one is able to make a notion of time as an abstract flow—that we call the thermal time—emerge from the knowledge of both: the algebra of observables of the physical system under investigation; a state of thermal equilibrium of this system. Formally, the thermal time is similar to the abstract flow of time in quantum mechanics, but we show in various examples that it may have a concrete implementation either as a geometrical flow or as a geometrical flow combined with a non-geometric action. This indicates that in quantum gravity, time may well still be “something that flows” at some abstract algebraic level, but this does not necessarily imply that time is always and only “something that flows” at the geometric level.


2013 ◽  
Vol 91 (1) ◽  
pp. 64-70 ◽  
Author(s):  
J. Sadeghi ◽  
A. Banijamali ◽  
E. Reisi

In this paper, using the Hamilton–Jacobi method we first calculate the Hawking temperature for a Horava–Lifshitz black hole. Then by utilizing the radial null geodesic method we obtain the entropy of such a black hole in four-dimensional space–time. We also consider the effect of back reaction on the surface gravity and compute modifications of entropy and Hawking temperature because of such an effect. Our calculations are for two kinds of Horava–Lifshitz black holes: Kehagias–Sfetsos and Lu–Mei–Pope.


2007 ◽  
Vol 22 (11) ◽  
pp. 2021-2045 ◽  
Author(s):  
C. CASTRO ◽  
J. A. NIETO

We study black hole-like solutions (space–times with singularities) of Einstein field equations in 3+1 and 2+2 dimensions. We find three different cases associated with hyperbolic homogeneous spaces. In particular, the hyperbolic version of Schwarzschild's solution contains a conical singularity at r = 0 resulting from pinching to zero size r = 0 the throat of the hyperboloid [Formula: see text] and which is quite different from the static spherically symmetric (3+1)-dimensional solution. Static circular symmetric solutions for metrics in 2+2 are found that are singular at ρ = 0 and whose asymptotic ρ→∞ limit leads to a flat (1+2)-dimensional boundary of topology S1 × R2. Finally we discuss the (1+1)-dimensional Bars–Witten stringy black hole solution and show how it can be embedded into our (3+1)-dimensional solutions. Black holes in a (2+2)-dimensional "space–time" from the perspective of complex gravity in 1+1 complex dimensions and their quaternionic and octonionic gravity extensions deserve furher investigation. An appendix is included with the most general Schwarzschild-like solutions in D ≥ 4.


2021 ◽  
Author(s):  
Wim Vegt

The “Hubble Constant” Value and specially the deviations in the “Hubble Constant” Value are one of the most fundamental parameters in our universe to understand the fine-structure of our 4-dimensional Space-Time continuum. Recent measurements with the “HST” of the “Hubble Constant” and the measured deviations[Ref. 17] reveal fundamental information of the fine-structure of our 4-dimensional Space-Time continuum. The recent measurements reveal a “Spherical Gravitational Indentation of approximately 10-10 [m/s2 ] with a diameter of approximately 2000 Mpc” surrounding our solar Milky Way Galaxy”. With increasing accuracies the need increases of a “New Theory in Physics” to explain the measured anomalies in the “Hubble Constant” value. Because “General Relativity” is not enough anymore to solve the nowadays problems in physics and specially in astronomy. With increasing accuracies the anomalies in the “Hubble Constant” value only become clearer. To develop a “New Theory in Physics” fundamental corrections have to be made in 2 of the 4 foundations in Physics. Corrections have to be made in Maxwell’s Electrodynamics and Bohr’s Quantum Mechanics. General Relativity will developed further to built the new theory in physics. Newton’s Classical dynamics will remain like it has always been. A solid ground to built on. Isaac Newton, James Clerk Maxwell, Niels Bohr and Albert Einstein lived in fundamentally different time frames. Newton in the 16th century, Maxwell in the 18th century, Bohr in the 20th century and Einstein was physically living in the 20th century but he was his time far ahead and with his concept of a “curved space-time continuum” more connected to the 21st century.


Author(s):  
Sribatsa Nanda

AbstractWe consider in this paper a topology (which we call the A-topology) on Minkowski space, the four-dimensional space–time continuum of special relativity and derive its group of homeomorphisms. We define the A-topology to be the finest topology on Minkowski space with respect to which the induced topology on time-like and light-like lines is one-dimensional Euclidean and the induced topology on space-like hyperplanes is three- dimensional Euclidean. It is then shown that the group of homeomorphisms of this topology is precisely the one generated by the inhomogeneous Lorentz group and the dilatations.


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