Banca de DEFESA: GABRIEL LUZ ALMEIDA

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
STUDENT : GABRIEL LUZ ALMEIDA
DATE: 18/07/2023
TIME: 09:00
LOCAL: online
TITLE:

Classical Amplitudes in Gravitational-Wave Physics

KEY WORDS:

Gravitational waves. Effective field theory. Post-Newtonian approximation. Radiation-reaction effects. Scattering
amplitudes.

PAGES: 135
BIG AREA: Ciências Exatas e da Terra
AREA: Física
SUMMARY:

The recent detections of gravitational waves from coalescing binaries by the LIGO and Virgo interferometers not
only opened a new window of observation into the Universe but also revived interest in the relativistic two-body problem. In
this thesis, after presenting the general theory of gravitational waves, we review the effective field theory approach within the
so-called Non-Relativistic General Relativity. In this framework, the different scales involved in the problem define different
dynamical regions, with short scales describing the conservative interaction between the two bodies and long-distance scales
accounting for gravitational-wave processes. At higher orders, however, radiation modes start to affect the conservative
dynamics of the system through the so-called tail effect.
We then study emission amplitudes for the class of nonlinear processes of tails, which are processes of order G_N^2, and
represent the effect of scattering gravitational radiation off the static background curvature, including not only mass tails but
also the “failed” tails due to the angular momentum of the source. As originally shown in our work, some of these amplitudes
present anomalies, which are then properly understood and corrected with field theory tools which have straightforward
counterpart in traditional methods. We also investigate the relation between emission and self-energy diagrams and, in
particular, show that a correction to the anomalous self-energy diagrams is necessary to correctly account for conservative
terms that arise from radiative processes. From this, we obtain the correct contribution to the conservative 5PN stemming from
the electric quadrupole angular momentum failed tail, correcting previous results of the literature. Besides this, we also
compute for the first time the conservative contributions from the angular momentum failed tail, for arbitrary multipole
moments.
Subsequently, we explore the natural higher-order extension (of order G_N^3) of the mass tails, called tails of tails, for generic
electric and magnetic multipoles. As we will see, both long- and short-distance divergences are encountered, which are then
properly understood and dealt with in terms of standard renormalization techniques. In this case, we are able to resum the
logarithmic contributions through the integration of the renormalization group equation.
Thus, in this thesis, we have extended the post-Newtonian perturbative expansion in the particularly thorny region of processes
involving the mixture of radiative and potential modes.

COMMITTEE MEMBERS:
Externa à Instituição - LAURA BERNARD
Externo à Instituição - WALTER GOLDBERGER
Interno - ***.839.841-** - DMITRY MELNIKOV - UFRN
Externo ao Programa - 2196137 - EMANUELE ORAZI - nullPresidente - ***.141.018-** - RICCARDO STURANI - UFRN