185 research outputs found
An extension of the Faddeev–Jackiw technique to fields in curved spacetimes
No full textThe Legendre transformation on singular Lagrangians, e.g. Lagrangians representing gauge theories, fails due to the presence of constraints. The Faddeev–Jackiw technique, which offers an alternative to that of Dirac, is a symplectic approach to calculating a Hamiltonian paired with a well-defined initial value problem when working with a singular Lagrangian. This phase space coordinate reduction was generalized by Barcelos-Neto and Wotzasek to simplify its application. We present an extension of the Faddeev–Jackiw technique for constraint reduction in gauge field theories and non-gauge field theories that are coupled to a curved spacetime that is described by general relativity. A major difference from previous formulations is that we do not explicitly construct the symplectic matrix, as that is not necessary. We find that the technique is a useful tool that avoids some of the subtle complications of the Dirac approach to constraints. We apply this formulation to the Ginzburg–Landau action and provide a calculation of its Hamiltonian and Poisson brackets in a curved spacetime.Massachusetts Institute of Technology. Dr. Martin Luther King, Jr. Visiting Professors and Scholars Progra
Do dark matter axions form a condensate with long-range correlation?
No full textRecently there has been significant interest in the claim that dark matter axions gravitationally thermalize and form a Bose-Einstein condensate with a cosmologically long-range correlation. This has potential consequences for galactic scale observations. Here we critically examine this claim. We point out that there is an essential difference between the thermalization and formation of a condensate due to repulsive interactions, which can indeed drive long-range order, and that due to attractive interactions, which can lead to localized Bose clumps (stars or solitons) that only exhibit short-range correlation. While the difference between repulsion and attraction is not present in the standard collisional Boltzmann equation, we argue that it is essential to the field theory dynamics, and we explain why the latter analysis is appropriate for a condensate. Since the axion is primarily governed by attractive interactions—gravitation and scalar-scalar contact interactions—we conclude that while a Bose-Einstein condensate is formed, the claim of long-range correlation is unjustified.United States. Dept. of Energy (Cooperative Research Agreement Contract DE-SC00012567)Massachusetts Institute of Technology (Dr. Martin Luther King, Jr. Visiting Professors and Scholars Program
Novel effects in self-interacting scalar field dark matter solitons
No full textSubmission original under an indefinite embargo labeled 'Open Access'. The submission was exported from vireo on 2025-10-20 without embargo termsThe student, Anthony Mirasola, accepted the attached license on 2025-07-18 at 16:19.The student, Anthony Mirasola, submitted this Dissertation for approval on 2025-07-18 at 16:34.This Dissertation was approved for publication on 2025-07-18 at 16:56.DSpace SAF Submission Ingestion Package generated from Vireo submission #22659 on 2025-10-20 at 20:15:28More than five-sixths of the matter in the universe is dark matter, a substance which cannot be seen and which interacts with other particles almost entirely through gravity. The identity of the dark matter is a longstanding open question. A class of models known as scalar field dark matter (SFDM) are exciting dark matter candidates that share common properties including the formation of solitons in the cores of dark matter halos. Solitons are energetically stable, gravitationally bound states of an extremely large number of SFDM particles that are the solutions to the classical equations of motion for SFDM, and in this work we present results of studies into their properties. We investigate the ability of solitons to emerge from virialized initial conditions in dark matter halos through kinetic relaxation and calculate the timescales associated with this process. We simulate rotating solitons which develop a unique vortex structure and study conditions under which the vortices can remain stable. We also explore models of SFDM which are expanded to include multiple species with both gravitational and non-gravitational inter-species interactions
“White Empiricism” and “The Racialization of Epistemology in Physics”: A Critical Analysis*
No full textI critically analyze the reasoning in Chanda Prescod-Weinstein’s article “Making Black women scientists under white empiricism: The racialization of epistemology in physics”
The New Era of Precision Cosmology: Testing Gravity at Large Scales
No full textCosmic acceleration may be the biggest phenomenological mystery in cosmology today. Various explanations for its cause have been proposed, including the cosmological constant, dark energy and modified gravities. Structure formation provides a strong test of any cosmic acceleration model because a successful dark energy model must not inhibit the development of observed large-scale structures. Traditional approaches to studies of structure formation in the presence of dark energy ore modified gravity implement the Press & Schechter formalism (PGF). However, does the PGF apply in all cosmologies? The search is on for a better understanding of universality in the PGF In this talk, I explore the potential for universality and talk about what dark matter haloes may be able to tell us about cosmology. I will also discuss the implications of this and new cosmological experiments for better understanding our theory of gravity
Cosmic Acceleration As Quantum Gravity Phenomenology
No full textThe discovery of cosmic acceleration has prompted the need for a new understanding of cosmology. The presence of this acceleration is often described as the dark energy problem or the Lambda problem.The simplest explanation is that the acceleration is due to addition of a cosmological constant to Einstein's equation, but this resolution is unsatisfactory as it leaves several unanswered questions. Although General Relativity has been tested in the strong-field limit, the apparent dark energy may be urging us to consider experimental cosmology as such a test for large scales. In this vein, I have pursued a study of modifications to Einstein's gravity as well as possible related quantum gravity phenomenology.
Not only must the details of modified gravities be worked out, but their impact on other astrophysics must be checked. For example, structure formation provides a strong test of any cosmic acceleration model because a successful dark energy model must not inhibit the development of observed large-scale structures. Traditional approaches to studies of structure formation in the presence of dark energy or a modified gravity implement the Press & Schechter formalism. I explore the potential for universality in the Press & Schechter formalism and what dark matter haloes may be able to tell us about cosmology
- …
