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The Alexander group explores the interconnection between the smallest and largest entities in the cosmos by using experimental data in cosmology and particle physics to test, constrain and improve on theories of quantum gravity and beyond the standard model of cosmology and particle physics.  Some questions we investigate are:

  • What happened at and before the big bang singularity?

  • What is the identity and nature of dark matter and dark energy?

  • Why does vacuum energy not gravitate (the cosmological constant problem)?

  • What is the origin of matter over anti-matter in the universe?

  • Can we use gravitational wave physics to probe fundamental physics?

  • What is the origin of large scale structure in the universe?

PRINCIPAL INVESTIGATOR
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STEPHON ALEXANDER

stephon_alexander [at] brown.edu

Stephon Alexander is a Professor of Physics at Brown University and former President of the National Society of Black Physicists (NSBP). Alexander has had previous appointments at Stanford University, Imperial College, Penn State, Dartmouth College, and Haverford College. He is a specialist in the field of string cosmology, where the physics of superstrings are applied to address longstanding questions in cosmology. In 2001, he co-invented the model of inflation based on higher dimensional hypersurfaces in string theory called D-Branes. In such models, the early universe emerged from the destruction of a higher dimensional D-brane which ignites a period of rapid expansion of space often referred to as cosmic inflation.

POST-DOCTORAL RESEARCHERS
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HUMBERTO B. GILMER 

humberto_gilmer [at] brown.edu 

Humberto Gilmer is a Post-Doctoral Research Fellow in the Department of Physics at Brown University and an NSF MPS-Ascending Fellow. His research interests lie broadly in Beyond-the-Standard Model physics, with particular attention paid to the intersection between cosmology and high energy physics, including dark matter, inflation, and new theories of gravity. He is also interested in more fundamental questions about the nature of field theory, such as the behavior of strongly-coupled theories or the nature and origin of mass.

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TUCKER MANTON

tucker_manton [at] brown.edu 

Tucker Manton is a Postdoctoral Research Associate in the Department of Physics at Brown University. His research spans three primary sub-disciplines: modifications to General Relativity, low-energy behavior of string theories with applications to cosmology, and a particular realization of gauge/gravity duality called the double copy. The double copy provides a framework for calculating gravitational observables using simpler, gauge theory quantities, and he has recently focused on pioneering new techniques with which to understand external sources in the double copy picture."

GRADUATE STUDENTS
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MICHAEL TOOMEY

michael_toomey [at] brown.edu 

Michael Toomey is a Ph.D. student in the Department of Physics at Brown University. His current research interests are broad, spanning astrophysics, cosmology, and high energy physics with an emphasis on applications of computation to problems from theory and phenomenology.  Some of his current and previous work includes establishing the feasibility of identifying blazars as progenitors of ultra-high-energy cosmic-rays, numerical simulations of the Galactic center excess, applications of machine learning to detect dark matter via lensing effects, constraining models of early dark energy in the context of large-scale structure, and novel applications of machine learning to problems in quantum gravity.

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TATSUYA DANIEL

tatsuya_daniel [at] brown.edu

Tatsuya (Tats) Daniel is a third-year Ph.D. student in the Department of Physics at Brown University with a research focus in Astro-Cosmo theory. His research interests include loop quantum gravity, corrections to Einstein's theory of General Relativity (GR), and cosmological models of the early universe. His current projects include probing theories of modified gravity using neutron stars as well as applications of the Kodama state, a zero-energy solution to the Schrödinger equation, in describing a background-independent formulation of quantum gravity. In the summer of 2021, Tats was an intern at Microsoft, where he worked on the triple correspondence between gauge theories, matrix models and neural networks to help build a computational "theory landscape explorer" tool for a universe that learns its own physical laws (an autodidactic universe).

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LAWRENCE EDMOND, IV

lawrence_edmond [at] brown.edu 

Lawrence Edmond, IV is a first-year Ph.D. student in the Department of Physics at Brown University. A University of California, Berkeley graduate with a degree in astronomy and astrophysics. His research interests include gravitational wave cosmology, black holes, and cosmological expansion. In Summer 2021, Lawrence was an intern at the Simons Research Institute where he studied gravitational lensing effects near binary black hole systems with Dr. Maria Okounkova. He is a member of the NSBP, a McNair Scholars alumnus, and a member of the Astronomy Scholars Program at UC Berkeley. In 2022, Lawrence studied the properties of the neutron star equation of state using gravitational waves with Drs. Carolyn Rathiel and Elias Most at Princeton University’s Gravity Initiative.

LAB ALUMNI

DANTE SANCHEZ

XIAO ZHOU