Research

The members of the group are interested in a wide range of topics in theoretical physics ranging from the physics of the early and late-time universe, modified gravity, gravitational waves and direct and indirect detection of dark matter. Members of our group also participate in international collaborations such as J-PAS, J-PLUS and LIGO.

Our research broadly falls into the following topics:

Cosmology (Ronaldo batista, Pedro Ferreira, Rodrigo Holanda, Léo Medeiros, Raimundo Silva):

 

Cosmology is the study of the universe as a whole, of its origin and evolution. Over the past few decades, a very good description of  the large-scale structure of the universe, the standard cosmological model (SCM), has emerged, incorporating into the highly successful standard big-bang scenario the results of cosmological observations and extending our understanding of the Universe to times as early as 10-35 sec, when the largest structures observed today were still quantum fluctuations.

The SCM assumes Einstein’s General Relativity and the Cosmological Principle and has the support of a set of independent observations, such as the Hubble diagram of type Ia supernovae, the temperature anisotropies of the cosmic microwave background and the pattern of galaxy clustering. In the context of the SCM, these observations suggest that we live in a flat, accelerating universe composed by ∼ 1/4 of matter (baryonic + dark) and ∼ 3/4 of an exotic component with large negative pressure, named dark energy. Our work aims at exploring observationally cosmological theories in order to better understand the universe’s evolution, especially the physical mechanisms behind the early and late-time cosmic acceleration.

Gravitation (Léo Medeiros, Janilo Santos, Riccardo Sturani):

Gravitational Waves

 

The recent historical detections of gravitational waves by the Laser Interferometer Gravitational wave Observatory (LIGO) marked the  beginning of a new science, Gravitational Wave Astronomy. The output of  gravitational wave  interferometric detector is particularly sensitive to the time behavior of the phase of the wave: in order to dig the signal out of the large detector noise it is crucial the availability of accurate analytic models of the gravitational waveform. Binary black holes have been defined as the “hydrogen atom of gravity”: they carry a clean and direct imprint of the fundamental gravitational dynamics ruling the binary dynamics and the wave emission, hence the observation of coalescing binary black holes allowed unprecedented tests of General Relativity.

Being part of the LIGO Scientific Collaboration, our work aims at maximizing the physics output of gravitational wave detections by improving on one side the data analysis techniques used in processing LIGO data and on the theoretical side by extending the analytic knowledge of the 2-body gravitational problem using methods borrowed from field theory.

Modified Gravity

 

Modifications in the structure of General Relativity (GR) have been proposed since its invention in the early 20th century motivated by different reasons, such attempts to build a quantum theory for gravity, generation of expansion regime in the universe, existence of possible extra dimensions, etc.  In recent years, however, a number of cosmological observations indicate that the present expansion of the Universe is accelerating. These findings led cosmologists to postulate the existence of an exotic component of dark energy, capable of explaining the accelerating rate while keeping GR unchanged. Alternatively, some researchers advanced the idea that perhaps we are observing the first deviations from GR on the largest scales.

Many of the elaborated proposals for GR extensions start with  modifications of the Einstein-Hilbert action. Among these proposals we can mention the f(R) theories – built from arbitrary functions of the Ricci scalar curvature – and the scalar-tensor theories, where part of the gravitational interaction is described by a scalar degree of freedom. The research line of modified gravity developed by our group follows mainly this kind of approach, with focus on scalar-tensor models and also investigating into whether f(R) theories are compatible with different kinds of currently available cosmological data.

Astroparticle Physics (Farinaldo Queiroz):

 

We are made of atoms and atoms are comprised of subatomic particles such as electrons and quarks. Nevertheless, atoms make up only 4% of the universe. The rest is unknown. Not totally unknown though because we have observational evidence that the universe is also occupied by some exotic matter that accounts for 85% of the entire matter content in our universe, also known as dark matter. There are about 10000 dark matter particles passing through a human body per year, but how come have we never caught one? Dark matter particles are part of our lives but we do not know their identity nor what they are made of.

Therefore, we are searching for new methods and data sets that could potentially represent a major step toward the nature of dark matter which is a major open problem in science. Projects along this line of research are intimately connected to the most important experiments worldwide in the search for dark matter. Moreover, we carry out projects that connect several observables in the context of theoretical particle physics such as the matter-antimatter asymmetry, flavor physics and model building and explore their collider signatures.