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 André G. S. Landulfo
Aguiar Alves, Níckolas de, and André G. S. Landulfo. 2025. “Null infinity as a Killing horizon.” Physical Review D 112 (6): 065017. arXiv: 2504.12514 [gr-qc].
Abstract: Symmetries are ubiquitous in modern physics. They not only allow for a more simplified description of physical systems but also, from a more fundamental perspective, can be seen as determining a theory itself. In the present paper, we propose a new definition of asymptotic symmetries that unifies and generalizes the usual notions of symmetry considered in asymptotically flat spacetimes and expanding universes with cosmological horizons. This is done by considering Bondi–Metzner–Sachs-like symmetries for “asymptotic (conformal) Killing horizons,” here defined as null hypersurfaces that are tangent to a vector field satisfying the (conformal) Killing equation in a limiting sense. The construction is theory agnostic and extremely general, for it makes no use of the Einstein equations and can be applied to a wide range of scenarios with different dimensions or hypersurface cross sections. While we reproduce the results by Dappiaggi, Moretti, and Pinamonti in the case of asymptotic Killing horizons, the conformal generalization does not yield only the Bondi–Metzner–Sachs group, but a larger group. The enlargement is due to the presence of “superdilations.” We speculate on many implications and possible continuations of this work, including the exploration of gravitational memory effects beyond general relativity, understanding antipodal matching conditions at spatial infinity in terms of bifurcate horizons, and the absence of superrotations in de Sitter spacetime and Killing horizons.
Tags: General Relativity, Infrared Physics, and Quantum Field Theory in Curved Spacetime
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