Jonas R. Mureika

Sub-Planckian black holes and the Generalized Uncertainty Principle

A bstractThe Black Hole Uncertainty Principle correspondence suggests that there could exist black holes with mass beneath the Planck scale but radius of order the Compton scale rather than Schwarzschild scale. We present a modified, self-dual Schwarzschild-like metric that reproduces desirable aspects of a variety of disparate models in the sub-Planckian limit, while remaining Schwarzschild in the large mass limit. The self-dual nature of this solution under M ↔ M−1 naturally implies a Generalized Uncertainty Principle with the linear form Δx∼1Δp+Δp

Aspects of noncommutative (1+1)-dimensional black holes

\Delta x\sim \frac{1}{\Delta p}+\Delta p

(1+1)-Dimensional Entropic Gravity

. We also demonstrate a natural dimensional reduction feature, in that the gravitational radius and thermodynamics of sub-Planckian objects resemble that of (1 + 1)-D gravity. The temperature of sub-Planckian black holes scales as M rather than M−1 but the evaporation of those smaller than 10−36 g is suppressed by the cosmic background radiation. This suggests that relics of this mass could provide the dark matter.

Self-completeness and spontaneous dimensional reduction

A bstractThe generalized uncertainty principle discloses a self-complete characteristic of gravity, namely the possibility of masking any curvature singularity behind an event horizon as a result of matter compression at the Planck scale. In this paper we extend the above reasoning in order to overcome some current limitations to the framework, including the absence of a consistent metric describing such Planck-scale black holes. We implement a minimum-size black hole in terms of the extremal configuration of a neutral non-rotating metric, which we derived by mimicking the effects of the generalized uncertainty principle via a short scale modified version of Einstein gravity. In such a way, we find a self-consistent scenario that reconciles the self-complete character of gravity and the generalized uncertainty principle.

Primordial Black Hole Evaporation and Spontaneous Dimensional Reduction

We present a comprehensive analysis of the spacetime structure and thermodynamics of (1 + 1)−dimensional black holes in a noncommutative framework. It is shown that a wider variety of solutions are possible than the commutative case considered previously in the literature. As expected, the introduction of a minimal length √ � cures singularity pathologies that plague the standard two-dimensional general relativistic case, where the latter solution is recovered at large length scales. Depending on the choice of input parameters (black hole mass M, cosmological constant �, etc...), black hole solutions with zero, up to six, horizons are possible. The associated thermodynamics allows for the either complete evaporation, or the production of black hole remnants.

Black hole thermodynamics in MOdified Gravity (MOG)

If the information transfer between test particle and holographic screen in entropic gravity respects both the uncertainty principle and causality, a lower limit on the number of bits in the universe relative to its mass may be derived. Furthermore, these limits indicate particles that putatively travel at the speed of light — the photon and/or graviton — have a nonzero mass m ≥10-68kg. This result is found to be in excellent agreement with current experimental mass bounds on the graviton and photon, suggesting that entropic gravity may be the result of a (recent) softly-broken local symmetry. Stronger bounds emerge from consideration of ultradense matter such as neutron stars, yielding limits of m ≥10-48–10-50kg, barely within the experimental photon range and outside that of the graviton. We find that for black holes these criteria cannot be satisfied, and suggest some possible implications of this result.

Vector unparticle enhanced black holes: Exact solutions and thermodynamics

Abstract We consider the formulation of entropic gravity in two spacetime dimensions. The usual gravitational force law is derived even in the absence of area, as normally required by the holographic principle. A special feature of this perspective concerns the nature of temperature and entropy defined at a point. We argue that the constancy of the gravitational force in one spatial dimension implies the information contained at each point in space is an internal degree of freedom on the manifold, and furthermore is a universal constant, contrary to previous assertions that entropic gravity in one spatial dimension is ill-defined. We give some heuristic arguments for gravitation and information transfer constraints within this framework, thus adding weight to the contention that spacetime and gravitation might be emergent phenomena.

Differentiating unparticles from extra dimensions via mini black hole thermodynamics

A viable quantum theory of gravity is one of the biggest challenges physicists are facing. We discuss the confluence of two highly expected features which might be instrumental in the quest of a finite and renormalizable quantum gravity —spontaneous dimensional reduction and self-completeness. The former suggests the spacetime background at the Planck scale may be effectively two-dimensional, while the latter implies a condition of maximal compression of matter by the formation of an event horizon for Planckian scattering. We generalize such a result to an arbitrary number of dimensions, and show that gravity in higher than four dimensions remains self-complete, but in lower dimensions it does not. In such a way we established an “exclusive disjunction” or “exclusive or” (XOR) between the occurrence of self-completeness and dimensional reduction, with the goal of actually reducing the unknowns for the scenario of the physics at the Planck scale. Potential phenomenological implications of this result are considered by studying the case of a two-dimensional dilaton gravity model resulting from dimensional reduction of the Einstein gravity.