Prof. Francisco S. N. Lobo

University of Lisbon

Prof. Francisco S. N. Lobo

University of Lisbon

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Academic Career Length

25Years (2002-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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13 July 2011 in Physical Review D

Journal Article

f (R, T)

We consider f(R,T) modified theories of gravity, where the gravitational Lagrangian is given by an arbitrary function of the Ricci scalar R and of the trace of the stress-energy tensor T. We obtain the gravitational field equations in the metric formalism, as well as the equations of motion for test particles, which follow from the covariant divergence of the stress-energy tensor. Generally, the gravitational field equations depend on the nature of the matter source. The field equations of several particular models, corresponding to some explicit forms of the function f(R,T), are also presented. An important case, which is analyzed in detail, is represented by scalar field models. We write down the action and briefly consider the cosmological implications of the f(R,T$\phi${}) models, where T$\phi${} is the trace of the stress-energy tensor of a self-interacting scalar field. The equations of motion of the test particles are also obtained from a variational principle. The motion of massive test particles is nongeodesic, and takes place in the presence of an extra-force orthogonal to the four velocity. The Newtonian limit of the equation of motion is further analyzed. Finally, we provide a constraint on the magnitude of the extra acceleration by analyzing the perihelion precession of the planet Mercury in the framework of the present model.

30 May 2007 in Physical Review D

Journal Article

Extra force in

f (R)

modified theories of gravity

The equation of motion for massive particles in

f (R)

modified theories of gravity is derived. By considering an explicit coupling between an arbitrary function of the scalar curvature,

R

, and the Lagrangian density of matter, it is shown that an extra force arises. This extra force is orthogonal to the four-velocity and the corresponding acceleration law is obtained in the weak-field limit. Connections with MOND and with the Pioneer anomaly are further discussed.

30 April 2025 in Astronomy & Astrophysics

Journal Article

Euclid

Euclid Collaboration

Y. Mellier

Abdurro’u F

J. A. Acevedo Barroso

A. Achúcarro

Ller Ller

+1138

The current standard model of cosmology successfully describes a variety of measurements, but the nature of its main ingredients, dark matter and dark energy, remains unknown. Euclid is a medium-class mission in the Cosmic Vision 2015–2025 programme of the European Space Agency (ESA) that will provide high-resolution optical imaging, as well as near-infrared imaging and spectroscopy, over about 14 000 deg² of extragalactic sky. In addition to accurate weak lensing and clustering measurements that probe structure formation over half of the age of the Universe, its primary probes for cosmology, these exquisite data will enable a wide range of science. This paper provides a high-level overview of the mission, summarising the survey characteristics, the various data-processing steps, and data products. We also highlight the main science objectives and expected performance.

31 August 2020 in General Relativity and Gravitation

Journal Article

Prospects for fundamental physics with LISA

Enrico Barausse

Emanuele Berti

Thomas Hertog

Scott A. Hughes

Philippe Jetzer

M. Zumalacarregui

+314

11 November 2009 in Physical Review D

Journal Article

Wormhole geometries in

f (R)

modified theories of gravity

Francisco S. N. Lobo

Miguel A. Oliveira

In this work, we construct traversable wormhole geometries in the context of

f (R)

modified theories of gravity. We impose that the matter threading the wormhole satisfies the energy conditions, so that it is the effective stress-energy tensor containing higher order curvature derivatives that is responsible for the null energy condition violation. Thus, the higher order curvature terms, interpreted as a gravitational fluid, sustain these nonstandard wormhole geometries, fundamentally different from their counterparts in general relativity. In particular, by considering specific shape functions and several equations of state, exact solutions for

f (R)

are found.

23 October 2010 in The European Physical Journal C

Journal Article

f(R,L m ) gravity

Tiberiu Harko

Francisco S. N. Lobo

We generalize the f(R) type gravity models by assuming that the gravitational Lagrangian is given by an arbitrary function of the Ricci scalar R and of the matter Lagrangian L _m. We obtain the gravitational field equations in the metric formalism, as well as the equations of motion for test particles, which follow from the covariant divergence of the energy-momentum tensor. The equations of motion for test particles can also be derived from a variational principle in the particular case in which the Lagrangian density of the matter is an arbitrary function of the energy density of the matter only. Generally, the motion is non-geodesic, and it takes place in the presence of an extra force orthogonal to the four-velocity. The Newtonian limit of the equation of motion is also considered, and a procedure for obtaining the energy-momentum tensor of the matter is presented. The gravitational field equations and the equations of motion for a particular model in which the action of the gravitational field has an exponential dependence on the standard general relativistic Hilbert–Einstein Lagrange density are also derived.

About Me

Francisco Lobo is the current coordinator of the Institute of Astrophysics and Space Sciences (IA). He is a researcher at the IA and Professor with Habilitation at the Department of Physics of the Faculty of Sciences of the University of Lisbon (FCUL). He was formerly the Leader of the IA-Cosmology Group (Unveiling the Dynamics of the Universe) and has been a member of the IA since its inception. He completed his PhD from the University of Lisbon in 2005. He is a member of the Euclid and LISA missions. He has published over 200 articles in high-impact international scientific journals and has participated in over 50 refereed conference proceedings; he has written over 25 book chapter(s) and 2 books [his h-index is the following: h=74 (INSPIRES); h=72 (NASA/ADS); h=78 (Google Scholar)]. He has supervised a significant number of MSc/PhD/post-docs and has been very successful in acquiring external funding. In the consecutive years of 2021 and 2022, he won the Ciências Research Award, a prize indicating that the FCUL distinguishes him as its most productive researcher in the previous year. In the consecutive years of the period 2018-2023, he was placed in the top 2% of a publicly available database, published by the PLoS Biology journal, of the world's 100,000 top scientists. He was the recipient of the 2021 Prémio Científico Universidade de Lisboa/Caixa Geral de Depósitos in the area of Physics.

Prof. Francisco S. N. Lobo

Prof. Francisco S. N. Lobo

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About Me