Research | rtso

Publications:

R.Tso, D. Gerosa, and Y. Chen: Optimizing LIGO with LISA forewarnings to vastly improve black-hole spectroscopy, PRD, 99, 124043 (2019). Press coverage: astrobites.
R.Tso, M. Isi, Y. Chen, and L. C. Stein (2016): Modeling the Dispersion and Polarization Content of Gravitational Waves for Tests of General Relativity, Proceedings of the Seventh Meeting on CPT and Lorentz Symmetry, pp. 205-208.
R.Tso and M. Zanolin: Measuring violations of General Relativity from single gravitational wave detection by non-spinning binary systems: higher-order asymptotic analysis, PRD, 93, 124033 (2016).
V.A.Kostelecký, N. Russell, and R.Tso : Bipartite Riemann-Finsler geometry and Lorentz violation, PLB, 716, 470-474 (2012).
R.Tso and Q.G. Bailey: Light-bending tests of Lorentz invariance, PRD, 84, 085025 (2011).
R.Tso and Q.G. Bailey (2010): Gravitational Lensing and Light Bending as Tests of Lorentz Symmetry, Proceedings of the Fifth Meeting on CPT and Lorentz Symmetry, pp. 283-286.

Other: INSPIRE (HEP).

Testing GR

Why?

For 100 years general relativity (GR) has been successful at characterizing gravity. Calculations first accounted for Mercury's orbital precession and later led to the famous 1919 light-bending confirmation measured by Dyson, Eddington, and Davidson. As a theory of spacetime, GR succeeded in correcting Newtonian dynamics wherever the pre-GR theory failed. In these early days, this was where the gravity's strength didn't exceed that of the Sun. Although GR superseded Newton's description, in certain limits the equations of GR can reduce to that of Newtonian theory. Conversely, corrections, appended to Newton's description, can be added as enhancements to the Newtonian theory to account for relativistic effects. In this manner, it can be argued that GR would've still emerged from corrections later uncovered through experiments. The idea is that without a full-fledge GR framework, as championed by many physicists of the early and mid 20th century, the systematic anomalies that would eventually transpire through astrophysical observations and particle physics experiments, to name a few, would've been studied to center on an understanding of relativity. Perhaps we'd have a murky understanding if this happened, perhaps a richer one, but it'd certainly have parallels to our current knowledge of relativity and its consequences.

As with every subject in physics, gravity has a theoretical component to complement its experimental foundation. Technological advances half a century after GR's discovery has allowed some of the most stringent experiments and observations to determine its validity as an accurate description of gravity. These tests were designed to probe proposed corrections to this already very successful theory of spacetime. Once observational techniques advanced, field strengths far greater than those of the solar system were examined. The Hulse-Taylor binary pulsar and observations on cosmological scales allowed further exploration of GR. To date, GR remains the most successful theory describing gravitation. From incorporating corrections through top-down approaches of some fundamental, or full/exact theory, to a bottom-up approach, with the notion that nature has some separation of scales, GR has been triumphant. Yet, scientists now approach the dawn of a new era of gravitational wave astronomy and tests of GR has just begun in its most extreme environments never before probed: supernovae, asymmetric pulsars, and compact binaries (e.g., binary black holes and neutron stars) with orbital velocities comparable to the speed of light.

What now?

My interest resides at the boundary of theory and observation, to test various theories of gravity, beyond that of GR, through GW observations. LIGO’s first observation run supplied two signals from the inspiral of two binary black hole pairs, gravitational wave events given the names GW150914 and GW151226 (numbers encoding the date of detection UTC time). Each detection gives signals at a scale where GR is still treated classically, rather than quantum-ly, yet allows the most relativistic regimes to be probed. Future runs have supplied even more detections, including GW170817 which is the first binary neutron star event. Combining all present and future detections will provide a wealth of information about how black holes behave, the nature of gravitational waves, and astrophysics. Contained within this information are constraints compatible with theories beyond GR. As a student at the intersection of theory and data analysis, and as a researcher between GR and beyond-GR, the task of finding if and when GR breaks down remains the ultimate goal.