Advances in High Energy Physics

Volume 2018, Article ID 7450607, 9 pages

https://doi.org/10.1155/2018/7450607

## Black Hole Thermodynamics and Generalized Uncertainty Principle with Higher Order Terms in Momentum Uncertainty

^{1}Department of Theoretical Sciences, S. N. Bose National Centre for Basic Sciences, JD Block, Sector III, Saltlake, Kolkata 700106, West Bengal, India^{2}Inter-University Centre for Astronomy & Astrophysics (IUCAA), Pune 411007, India^{3}Department of Physics, West Bengal State University, Barasat, Kolkata 700126, India^{4}Department of Physics, Kandi Raj College, Kandi, Murshidabad 742137, India

Correspondence should be addressed to Sunandan Gangopadhyay; moc.liamg@yayhdapognag.nadnanus

Received 31 January 2018; Revised 16 April 2018; Accepted 23 April 2018; Published 7 June 2018

Academic Editor: George Siopsis

Copyright © 2018 Sunandan Gangopadhyay and Abhijit Dutta. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. The publication of this article was funded by SCOAP^{3}.

#### Abstract

We study the modification of thermodynamic properties of Schwarzschild and Reissner-Nordström black hole in the framework of generalized uncertainty principle with correction terms up to fourth order in momentum uncertainty. The mass-temperature relation and the heat capacity for these black holes have been investigated. These have been used to obtain the critical and remnant masses. The entropy expression using this generalized uncertainty principle reveals the area law up to leading order logarithmic corrections and subleading corrections of the form . The mass output and radiation rate using Stefan-Boltzmann law have been computed which show deviations from the standard case and the case with the simplest form for the generalized uncertainty principle.

#### 1. Introduction

The consistent unification of quantum mechanics (QM) with general relativity (GR) is one of the major tasks in theoretical physics. GR deals with the definition of world-lines of particles, which is in contradiction with QM since it does not allow the notion of trajectory due to the presence of an uncertainty in the determination of the momentum and position of a quantum particle. It has been the aim to unify these two theories into one theory known as quantum gravity. It is quite interesting that all approaches towards quantum gravity such as black hole physics [1–3], string theory [4, 5], or even* Gedanken* experiment [6] predict the existence of a minimum measurable length. The occurrence of such a minimal length also arises in various theories of quantum gravity phenomenology, namely, the generalized uncertainty principle (GUP) [5, 7, 8], modified dispersion relation (MDR) [9–12], and deformed special relativity (DSR) [13], to name a few. It is now widely accepted that Heisenberg uncertainty principle would involve corrections from gravity at energies close to the Planck scale. Thus, emergence of a minimal length seems to be inevitable when gravitational effects are taken into account. There has been a lot of work incorporating the existence of a minimal length scale in condensed matter and atomic physics experiments such as Lamb Shift, Landau levels and the scanning Tunneling Microscope [14–19], loop quantum gravity [20–22], noncommutative geometry [23], computing Planck scale corrections to the phenomena of superconductivity and quantum Hall effect [24], and understanding its consequences in cosmology [25, 26].

The incorporation of the GUP to study black hole thermodynamics has been another interesting area of active research [27–38]. It has been observed that the GUP reveals a self-complete characteristic of gravity which basically amounts to hiding any curvature singularity behind an event horizon as a consequence of matter compression at the Planck scale [39–41]. Further, the effects of the GUP have also been considered in the tunneling formalism for Hawking radiation to evaluate the quantum-corrected Hawking temperature and entropy of a Schwarzschild black hole [42–46]. In our earlier findings [32–36], we have studied the modification of thermodynamic properties, namely, the temperature, heat capacity, and entropy of black holes due to the simplest form of the GUP. Interestingly the correction to the Schwarzschild black hole temperature due to quadratic and linear-quadratic GUP has also been compared with the corrections from the quantum Raychaudhuri equation [47]. Very recently the Lorentz-invariance-violating class of dispersion relations has been applied to study the thermodynamics of black holes [48]. It would therefore be interesting to compare these results with those coming from the GUP.

The above studies motivate us to investigate the modification of thermodynamic properties for Schwarzschild and Reissner-Nordström (RN) black holes using the form of the GUP proposed in [30]. This GUP involves higher order terms in the momentum uncertainty. We compute the remnant and critical masses analytically for these black holes below where the temperature becomes ill-defined. We then use the Stefan-Boltzmann law to estimate the mass and the energy output as a function of time. We finally compute the entropy and obtain the well-known area theorem containing corrections from the GUP with higher order terms in momentum uncertainty.

The paper is organized as follows. In Section 2, we study the thermodynamics of Schwarzschild black hole taking into account the effect of the GUP, with higher order terms in momentum uncertainty. In Section 2.1, we also obtain the mass and radiation rate characteristics for the Schwarzschild black hole as a function of time by using the Stefan-Boltzmann law. In Section 3, we study the thermodynamics of Reissner-Nordström black holes taking into account the effect of the GUP. Finally, we conclude in Section 4.

#### 2. Thermodynamics of Schwarzschild Black Hole

In this paper, we work with the following form of the GUP [49]:where is the Planck length (). Keeping terms up to fourth order in momentum uncertainty, we haveWe now consider a Schwarzschild black hole of mass . In the vicinity of the event horizon of the black hole, let a pair (particle-antiparticle) production occurs. For simplicity we consider the particle to be massless. The particle with negative energy falls inside the horizon and that with positive energy escapes outside the horizon and gets observed by some observer at infinity. The momentum of the emitted particle (p), which also characterizes the temperature (T), is of the order of its uncertainty in momentum . Consequentlywhere is the speed of light and is the Boltzmann constant.

The Hawking temperature of the black hole will be equal to the temperature of the particle when thermodynamic equilibrium is reached. The uncertainty in the position of a particle near the event horizon of the Schwarzschild black hole will be of the order of the Schwarzschild radius of the black holewhere is a calibration factor, is the Schwarzschild radius, and is Newton’s universal gravitational constant.

To relate the Hawking temperature of the black hole with the mass of the black hole, we consider the saturated form of the GUP (2)Substituting (3) and (4) in (5) giveswhere the relations and ( being the Planck mass) have been used. In the absence of corrections due to GUP, (6) reduces toThe value of now gets fixed to by comparing this expression with the semiclassical Hawking temperature [50, 51]. The mass-temperature relation (6) finally takes the formThe heat capacity of the black hole therefore readsThe above expression takes the formafter the following notations are introducedThe mass of the black hole decreases due to radiation from the black hole. This leads to an increase in the temperature of the black hole. It can be observed from (7) and (10) that there exists a finite temperature at which the heat capacity vanishes. To find out this temperature, we set C = 0. This givesSolving this, we getwhere the positive sign before the square root has been taken so that the above result reduces to corresponding result when [33].

Finally we get the expression for to beNow in terms of , the mass-temperature relation (8) can be represented asThe remnant mass can now be obtained by substituting (15) in (16). This yieldsReassuringly the above result reduces to the result in limit [33]Now for , , the remnant mass is given byAlso for , the mass-temperature relation (16) readsThe solution of this biquadratic equation in yieldsThe above relation readily implies the existence of a critical mass below which the temperature will be a complex quantityThis demonstrates that the remnant and critical masses are equal.

At this point, we would like to make a comment. It can be observed from the above analysis that analytical expressions for the remnant and critical masses can be obtained even if one retains terms of order of in the momentum uncertainty. This is because it leads to an equation of the form when the condition is imposed. This equation can be solved analytically to obtain the remnant mass. If we keep terms beyond this order in momentum uncertainty, analytical expressions for the remnant and critical masses can not be obtained.

The black hole entropy from the first law of black hole thermodynamics is given byTo obtain the entropy S in terms of the mass M of the black hole, we need to consider (16) to obtain an expression for the temperature T in terms of mass M.

Equation (16) yields up to Now the entropy expression in terms of the mass can be written aswhere is the semiclassical Bekenstein-Hawking entropy for the Schwarzschild black hole. In terms of the black hole horizon area , the above entropy expression can be written asThis completes our discussion of the effect of the GUP on the thermodynamic properties of the Schwarzschild black hole. In Figure 1, we present the plot of the entropy of the black hole versus the horizon area for the GUP case and compare it with the standard case.