Constraining the tidal charge of brane black holes using their shadows

A constraint on the tidal charge generated within a brane world is shown. Using the shadow of a rotating black hole in a brane context in order to describe the M87* parameters recently announced by the Event Horizon Telescope Collaboration, the deviation from circularity of the reported shadow produces an upper bound on the bulk's nonlocal effect, which is conceived of as a tidal charge in the four-dimensional brane induced by the five-dimensional bulk. Therefore, a deviation from circularity $\lesssim 10\%$ leads to an upper bound on the tidal charge $\lesssim 0.004M^2$.Comment: 9 pages, 2 figures, 1 table. V2 with minor changes and new references. Published in The European Physical Journal

Nietzsche for physicists

One of the most important philosophers in history, the German Friedrich Nietzsche, is almost ignored by physicists. This author who declared the death of God in the 19th century was a science enthusiast, especially in the second period of his work. With the aid of the physical concept of force, Nietzsche created his concept of will to power. After thinking about energy conservation, the German philosopher had some inspiration for creating his concept of eternal recurrence. In this article, some influences of physics on Nietzsche are pointed out, and the topicality of his epistemological position$-$the perspectivism$-$is discussed. Considering the concept of will to power, I propose that the perspectivism leads to an interpretation where physics and science in general are viewed as a game.Comment: 14 pages. Version 3 with improvements, corrections. Accepted in Philosophia Scientia

Thermodynamics of a class of regular black holes with a generalized uncertainty principle

In this article, we present a study on thermodynamics of a class of regular black holes. Such a class includes Bardeen and Hayward regular black holes. We obtained thermodynamic quantities like the Hawking temperature, entropy, and heat capacity for the entire class. As part of an effort to indicate some physical observable to distinguish regular black holes from singular black holes, we suggest that regular black holes are colder than singular black holes. Besides, contrary to the Schwarzschild black hole, that class of regular black holes may be thermodynamically stable. From a generalized uncertainty principle, we also obtained the quantum-corrected thermodynamics for the studied class. Such quantum corrections provide a logarithmic term for the quantum-corrected entropy.Comment: 8 pages, 1 figure. Version with corrected typos. Accepted in Physical Review

Special theory of regularity

The theory of regularity is a philosophical perspective in which laws of nature are just descriptions, that is to say, laws of nature do not govern the world. Moreover, according to the theory of regularity, the number of laws of nature might be infinite, thus any attempt towards the theory of everything is doomed. Here I propose a special or restricted theory of regularity. The main difference as to the well-known version of that theory is both the range of validity and the scale of the laws of nature. Laws of nature ought to be considered just inside the observable universe and within certain energy and length scales. Even so I apply the theory of regularity to the multiverse scenario. As a consequence, the special theory of regularity supports only two types of multiverses by comparison with our world: those ones with a different sequence of unique events and different laws of nature and those ones with the same sequence of unique events and the same laws of nature instanced by the unique events. The latter case is some sort of eternal recurrence or a parallel eternal recurrence.Comment: 17 page