We study the one-loop contributions of matter and radiation to the gravitational polarization tensor at finite temperatures. Using the analytically continued imaginary-time formalism, the contribution of matter is explicitly given to next-to-leading ($T^2$) order. We obtain an exact form for the contribution of radiation fields, expressed in terms of generalized Riemann zeta functions. A general expression is derived for the physical polarization tensor, which is independent of the parametrization of graviton fields. We investigate the effective thermal masses associated with the normal modes of the corresponding graviton self-energy.Comment: 32 pages, IFUSP/P-107

We study non-perturbatively, via the Schwinger-Dyson equations, the leading infrared behavior of the pressure in the ladder approximation. This problem is discussed firstly in the context of a thermal scalar field theory, and the analysis is then extended to the Yang-Mills theory at high temperatures. Using the Feynman gauge, we find a system of two coupled integral equations for the gluon and ghost self-energies, which is solved analytically. The solutions of these equations show that the contributions to the pressure, when calculated in the ladder approximation, are finite in the infrared domain.

We study finite-temperature effects to one-loop order in field theories by relating them to the forward scattering of thermal particles. This approach allows for an exact evaluation of all temperaturedependent contributions to the thermal self-energy in terms of generalized ( functions. We obtain a closed-form expression for the two-point gluon function in thermal Yang-Mills theory.

In nature, confrontations between conspecifics are recurrent and related, in general, due to the lack of resources such as food and territory. Adequate defence against a conspecific aggressor is essential for the individual's survival and the group integrity. However, repeated social defeat is a significant stressor promoting several behavioural changes, including social defence per se . What would be the neural basis of these behavioural changes? To build new hypotheses about this, we here investigate the effects of repeated social stress on the neural circuitry underlying motivated social defence behaviour in male mice. We observed that animals re-exposed to the aggressor three times spent more time in passive defence during the last exposure than in the first one. These animals also show less activation of the amygdalar and hypothalamic nuclei related to the processing of conspecific cues. In turn, we found no changes in the activation of the hypothalamic dorsal pre-mammillary nucleus (PMD) that is essential for passive defence. Therefore, our data suggest that the balance between the activity of circuits related to conspecific processing and the PMD determines the pattern of social defence behaviour. Changes in this balance may be the basis of the adaptations in social defence after repeated social defeat.

In nature, confrontations between conspecifics are recurrent and related, in general, to the lack of resources such as food and territory. In this sense, adequate defence against a conspecific aggressor is essential for the individual’s survival and the group integrity. However, repeated social defeat is a significant stressor, promoting several behavioural changes, including on social defence per se. But what would be the neural basis of these behavioural changes? To explore some hypotheses about this, we investigated the effects of repeated social stress on neural circuits underlying the motivated behaviour social defence in male mice. The hypothalamus is an essential centre of these circuits. Different hypothalamic structures receive information about the conspecific from the medial amygdala and the bed nucleus of the terminal stria. Furthermore, the hypothalamus can receive environmental information via the septo-hippocampal-hypothalamic circuit. Both information is processed by the dorsal premammillary nucleus (PMD) and the ventrolateral portion of the ventromedial nucleus of the hypothalamus, which communicate with the periaqueductal grey, an important downstream site for behavioural emission. During our analysis, we observed that animals re-exposed three times to the aggressor spent more time in passive defence during their last exposure than in their first one. These animals also present a smaller mobilization of areas related to the processing of conspecific cues. In contrast, we did not observe changes in the PMD mobilization. Therefore, our data indicate that the balance between the activity of circuits related to conspecific processing and the PMD determines the pattern of social defence behaviour. Changes in this balance may be the basis of the adaptations in social defence after repeated social defeat.