arXiv subjects

Narit Pidokrajt

Publications and source records attributed to Narit Pidokrajt.

14 recordsLinked to original sources

arXiv2021

Understanding the physics of world's fastest non-motorized sport

The main objective of this article is to describe the physics of Speed Skydiving, world's fastest non-motorized sport practiced under FAI -- Fédération Aéronautique Internationale (World Air Sports Federation), a recognized body by the International Olympic Committee -- with the help of standard physics and mathematics taught during the first or second year for undergraduate students in physics worldwide. Although this discipline of air sports has been around since the middle of the 1990s and has been a part of major international sport events, it is not yet well-known to the wider public and has not been addressed thoroughly in physics textbooks as the physics of various other sports. It is hoped that this paper will introduce and engage physics teachers/instructors new to this air sport discipline -- pedagogically. University or high school students may find this article helpful while studying a subject of terminal speeds, which is thoroughly discussed herein. This article can also serve as a background for further studies in physics of skydiving and aerodynamics.

physics.ed-ph↗

arXiv2015

Thermodynamic Metrics and Black Hole Physics

We give a brief survey of thermodynamic metrics, in particular the Hessian of the entropy function, and how they apply to black hole thermodynamics. We then provide a detailed discussion of the Gibbs surface of Kerr black holes. In particular we analyze its global properties, and extend it to take the entropy of the inner horizon into account. A brief discussion of Kerr-Newman black holes is included.

gr-qc↗

arXiv2011

Thermodynamic Geometry and Type 0A Black Holes

In this note we study thermodynamic geometry of the type 0A black hole solution in string theory using a variety of different methods (Ruppeiner, Weinhold and Geometrothermodynamics). Our results indicate that the curvature invariants are finite for all physical solutions, suggesting that there is no phase transition. It is also found that the cutoff of the entropy, which is the singular limit of the theory, appears geometrically in the Weinhold picture as the thermodynamic cone itself.

gr-qc↗

arXiv2011

Geometro-thermodynamics of tidal charged black holes

Tidal charged spherically symmetric vacuum brane black holes are characterized by their mass m and tidal charge q, an imprint of the 5-dimensional Weyl curvature. For q>0 they are formally identical to the Reissner-Nordström black hole of general relativity. We study the thermodynamics and thermodynamic geometries of tidal charged black holes and discuss similarities and differences as compared to the Reissner-Nordström black hole. As a similarity, we show that (for q>0) the heat capacity of the tidal charged black hole diverges on a set of measure zero of the parameter space, nevertheless both the regularity of the Ruppeiner metric and a Poincaré stability analysis shows no phase transition at those points. The thermodynamic state spaces being different indicates that the underlying statistical models could be different. We find that the q<0 parameter range, which enhances the localization of gravity on the brane, is thermodynamically preferred. Finally we constrain for the first time the possible range of the tidal charge from the thermodynamic limit on gravitational radiation efficiency at black hole mergers.

gr-qc↗

arXiv2010

On explicit thermodynamic functions and extremal limits of Myers-Perry black holes

We study thermodynamic properties of Myers-Perry black holes by deriving explicit fundamental relations from which we can obtain the temperature and specific heat in terms of explicit control parameters in arbitrary dimensions. Using the definition of extremal black holes we establish the generalized Kerr bound in arbitrary dimension. We study thermodynamic geometries of the Myers-Perry black holes with equal angular momenta in arbitrary dimensions and draw thermodynamic cone diagrams which capture the extremal limits of the black holes. Thermodynamic state space is represented geometrically as a wedge embedded in Minkowski space. The opening angle of such a wedge is uniquely determined by the number of spacetime dimensions and the number of angular momenta. Our results can potentially be used to generalize thermodynamic instability analysis and other studies in which extremal limits of the Myers-Perry black holes are required.

hep-th↗

arXiv2010

Critical phenomena and information geometry in black hole physics

We discuss the use of information geometry in black hole physics and present the outcomes. The type of information geometry we utilize in this approach is the thermodynamic (Ruppeiner) geometry defined on the state space of a given thermodynamic system in equilibrium. The Ruppeiner geometry can be used to analyze stability and critical phenomena in black hole physics with results consistent with those from the Poincare stability analysis for black holes and black rings. Furthermore other physical phenomena are well encoded in the Ruppeiner metric such as the sign of specific heat and the extremality of the solutions. The black hole families we discuss in particular in this manuscript are the Myers-Perry black holes.

gr-qc↗

arXiv2009

Information geometry of asymptotically AdS black holes

We investigate thermodynamic geometries of two families of asymptotically Anti-de Sitter black holes, i.e. the Reissner-Nordström Anti-de Sitter in four dimensions and the BTZ black hole. It is found that the Anti-de Sitter space renders the geometry nontrivial (c.f. the Reissner-Nordström black hole in asymptotically flat background). The BTZ black hole's thermodynamic geometry is trivial despite the fact that it is characterized by the (negative) cosmological constant. As a matter of curiosity we compute thermodynamic geometry of these black holes regarding the cosmological constant as a true parameter but no physically significant results can be derived.

gr-qc↗

arXiv2008

Anti-de Sitter Quotients, Bubbles of Nothing, and Black Holes

In 3+1 dimensions there are anti-de quotients which are black holes with toroidal event horizons. By analytic continuation of the Schwarzschild-anti-de Sitter solution (and appropriate identifications) one finds two one parameter families of spacetimes that contain these quotient black holes. One of these families consists of B-metrics ("bubbles of nothing"), the other of black hole spacetimes. All of them have vanishing conserved charges.

hep-th↗

arXiv2007

Ruppeiner Geometry of Black Hole Thermodynamics

The Hessian of the entropy function can be thought of as a metric tensor on state space. In the context of thermodynamical fluctuation theory Ruppeiner has argued that the Riemannian geometry of this metric gives insight into the underlying statistical mechanical system; the claim is supported by numerous examples. We study these geometries for some families of black holes and find that the Ruppeiner geometry is flat for Reissner--Nordström black holes in any dimension, while curvature singularities occur for the Kerr black holes. Kerr black holes have instead flat Weinhold curvature.

gr-qc↗

arXiv2007

On Geometro-thermodynamics of Dilaton Black Holes

In this talk we present the latest results from our ongoing project on geometro-thermodynamics (also known as information geometry of thermodynamics or Ruppeiner geometry) of dilaton BHs in 4D in both Einstein and string frames and a dyonic dilaton BH and at the end we report very briefly results from this approach to the 2D dilaton BHs.

hep-th↗

arXiv2006

Ruppeiner theory of black hole thermodynamics

The Ruppeiner metric as determined by the Hessian of the Gibbs surface provides a geometric description of thermodynamic systems in equilibrium. An interesting example is a black hole in equilibrium with its own Hawking radiation. In this article, we present results from the Ruppeiner study of various black hole families from different gravity theories e.g. 2D dilaton gravity, BTZ, general relativity and higher-dimensional Einstein-Maxwell gravity.

gr-qc↗

arXiv2006

Flat Information Geometries in Black Hole Thermodynamics

The Hessian of either the entropy or the energy function can be regarded as a metric on a Gibbs surface. For two parameter families of asymptotically flat black holes in arbitrary dimension one or the other of these metrics are flat, and the state space is a flat wedge. The mathematical reason for this is traced back to the scale invariance of the Einstein-Maxwell equations. The picture of state space that we obtain makes some properties such as the occurence of divergent specific heats transparent.

gr-qc↗

arXiv2006

Geometry of Higher-Dimensional Black Hole Thermodynamics

We investigate thermodynamic curvatures of the Kerr and Reissner-Nordström (RN) black holes in spacetime dimensions higher than four. These black holes possess thermodynamic geometries similar to those in four dimensional spacetime. The thermodynamic geometries are the Ruppeiner geometry and the conformally related Weinhold geometry. The Ruppeiner geometry for $d=5$ Kerr black hole is curved and divergent in the extremal limit. For $d \geq 6$ Kerr black hole there is no extremality but the Ruppeiner curvature diverges where one suspects that the black hole becomes unstable. The Weinhold geometry of the Kerr black hole in arbitrary dimension is a flat geometry. For RN black hole the Ruppeiner geometry is flat in all spacetime dimensions, whereas its Weinhold geometry is curved. In $d \geq 5$ the Kerr black hole can possess more than one angular momentum. Finally we discuss the Ruppeiner geometry for the Kerr black hole in $d=5$ with double angular momenta.

hep-th↗

arXiv2003

Geometry of black hole thermodynamics

The Hessian of the entropy function can be thought of as a metric tensor on the state space. In the context of thermodynamical fluctuation theory Ruppeiner has argued that the Riemannian geometry of this metric gives insight into the underlying statistical mechanical system; the claim is supported by numerous examples. We study this geometry for some families of black holes. It is flat for the BTZ and Reissner-Nordstrom black holes, while curvature singularities occur for the Reissner-Nordstrom-anti-de Sitter and Kerr black holes.

gr-qc↗