This page lists my papers and preprints. Clicking on a title will take you to a page summarizing the paper's main results.
Níckolas de Aguiar Alves and Bruno Arderucio Costa
Aguiar Alves, Níckolas de, and Bruno Arderucio Costa. 2025. “The Measure of a Mass.” Essay written for the Gravity Research Foundation 2025 Awards for Essays on Gravitation. arXiv: 2503.18963 [gr-qc].
Abstract: The concept of mass is central to any theory of gravity. Nevertheless, defining mass in general relativity is a difficult task, and even when it can be accomplished, we still need to investigate whether the typical properties of mass in Newtonian gravity are still true in Einsteinian gravity. In this essay, we discuss "the measure of a mass" in relativity by considering some of the many different definitions (Komar, ADM, and Bondi) and how they are related. Finally, we discuss when and whether the mass is positive, as is usually expected, and which physical properties of matter and gravity can ensure this result.
Tags: General Relativity and Energy Conditions
Níckolas de Aguiar Alves, André G. S. Landulfo, and Bruno Arderucio Costa
Aguiar Alves, Níckolas de, André G. S. Landulfo, and Bruno Arderucio Costa. 2025. “Positive Mass in General Relativity Without Energy Conditions.” Physical Review D 111 (4): 044027. arXiv: 2408.00154 [gr-qc].
Abstract: A long-standing problem in physics is why observed masses are always positive. While energy conditions in quantum field theory can partly answer this problem, in this paper we find evidence that classical general relativity abhors negative masses, without the need for quantum theory or energy conditions. This is done by considering many different models of negative-mass "stars" and showing they are dynamically unstable. A fortiori, we show that any barotropic negative-mass star must be dynamically unstable.
Tags: General Relativity and Energy Conditions