arXiv subjects

Jean-Pierre Luminet

Publications and source records attributed to Jean-Pierre Luminet.

At least 19 recordsLinked to original sources

arXiv2025

A Primer on Spacetime Singularities I: Mathematical Framework

This article presents a comprehensive and rigorous overview of spacetime singularities within the framework of classical General Relativity. Singularities are defined through the failure of geodesic completeness, reflecting the limits of predictability in spacetime evolution. The paper reviews the mathematical structures involved, including differentiability classes of the metric, and explores key constructions such as Geroch's and Schmidt's formulations of singular boundaries. A detailed classification of singularities - quasi-regular, non-scalar, and scalar - is proposed, based on the behavior of curvature tensors along incomplete curves. The limitations of previous approaches, including the cosmic censorship conjecture and extensions beyond General Relativity, are critically examined. The work also surveys the major singularity theorems of Penrose and Hawking, emphasizing their implications for gravitational collapse and cosmology. By focusing exclusively on the classical regime, the article lays a solid foundation for the systematic study of singular structures in relativistic spacetimes.

gr-qc↗

arXiv2023

Big Bang Cosmology and Religious Thought

Alexander Friedmann and Georges Lemaître are undoubtedly the real fathers of Big Bang cosmologies. In this article I study the influences their work underwent due to some religious as well as anti-religious ideas. During his career Lemaître faced criticisms coming from non-believing scientists, who reproached him (wrongly) to have developed his primeval atom cosmology for conciliatory reasons. In the former case of Friedmann, we know that his 1922 proposal of a "creation of the world out of nothing" was criticized by Einstein for metaphysical reasons. The essence of such hostile reactions is the fact that presumably "good" scientific contents should not be influenced by religious ideas. Nevertheless, metaphysical and theological ideas can play an important role inside the science research processes, as an epistemological tool helping to clarify the use of some fundamental notions.

physics.hist-ph↗

arXiv2021

Closed Timelike Curves, Singularities and Causality: A Survey from Gödel to Chronological Protection

I give a historical survey of the discussions about the existence of closed timelike curves in general relativistic models of the universe, opening the physical possibility of time travel in the past, as first recognized by K. Gödel in his rotating universe model of 1949. I emphasize that journeying into the past is intimately linked to spacetime models devoid of timelike singularities. Since such singularities arise as an inevitable consequence of the equations of general relativity given physically reasonable assumptions, time travel in the past becomes possible only when one or another of these assumptions is violated. It is the case with wormhole-type solutions. S. Hawking and other authors have tried to "save" the paradoxical consequences of time travel in the past by advocating physical mechanisms of chronological protection; however, such mechanisms remain presently unknown, even when quantum fluctuations near horizons are taken into account. I close the survey by a brief and pedestrian discussion of Causal Dynamical Triangulations, an approach to quantum gravity in which causality plays a seminal role.

gr-qc↗

arXiv2021

The Dark Matter Enigma

In this pedestrian approach I give my personal point of view on the various problems posed by dark matter in the universe. After a brief historical overview I discuss the various solutions stemming from high energy particle physics, and the current status of experimental research on candidate particles (WIMPS). In the absence of direct evidence, the theories can still be evaluated by comparing their implications for the formation of galaxies, clusters and superclusters of galaxies against astronomical observations. I conclude briefly with the attempts to circumvent the dark matter problem by modifying the laws of gravity.

physics.pop-ph↗

arXiv2019

An Illustrated History of Black Hole Imaging : Personal Recollections (1972-2002)

The Event Horizon Telescope Consortium is on the verge to provide the first telescopic image of massive black holes SgrA* and M87* surrounded by accretion disks, at a resolution scale comparable to the size of their event horizons. Well before this remarkable achievement made possible by VLBI radio astronomy, many researchers used the computer to reconstruct how a black hole surrounded by luminous material would look from close-up views. The images must experience extraordinary optical deformations due to the deflection of light rays produced by the strong curvature of the space-time in the vicinity. General relativity allows the calculation of such effects, both on a surrounding accretion disk and on the background star field. This article is an exhaustive and illustrated review of the numerical work on black hole imaging done during the first thirty years of its history.

astro-ph.HE↗

arXiv2018

Gravitational Music

Since the 1960s a growing number of composers have engaged with scientific research and have tried to incorporate their understanding of various models and theories into their musical works. Among them, Hèctor Parra (b. 1976) has been particularly impressed by the recent developments of gravitational physics and astrophysics, namely the part of astronomy which deals with gravity rather than light. Black holes, gravitational waves (first detected in September 2015), cosmology, or quantum gravity models belong to such fields of intensive research, bringing surprising new concepts such as the coarse-graining of space-time, multiverse or holographic principle. In this framework we have collaborated in the conception of a large piece for soloist ensemble, orchestra and electronic devices, which tries to transpose gravitational phenomena into a new form of contemporary music.

physics.pop-ph↗

arXiv2018

Seeing Black Holes : from the Computer to the Telescope

Astronomical observations are about to deliver the very first telescopic image of the massive black hole lurking at the Galactic Center. The mass of data collected in one night by the Event Horizon Telescope network, exceeding everything that has ever been done in any scientific field, should provide a recomposed image during 2018. All this, forty years after the first numerical simulations done by the present author.

astro-ph.IM↗

arXiv2017

The Reception of the Copernican Revolution Among Provençal Humanists of the Sixteenth and Seventeenth Centuries

We discuss the reception of Copernican astronomy by the Provençal humanists of the XVIth-XVIIth centuries, beginning with Michel de Montaigne who was the first to recognize the potential scientific and philosophical revolution represented by heliocentrism. Then we describe how, after Kepler's Astronomia Nova of 1609 and the first telescopic observations by Galileo, it was in the south of France that the New Astronomy found its main promotors with the humanists and "amateurs éclairés", Nicolas-Claude Fabri de Peiresc and Pierre Gassendi. The professional astronomer Jean-Dominique Cassini, also from Provence, would later elevate the field to new heights in Paris.

physics.hist-ph↗

arXiv2016

Creation, Chaos, Time : from Myth to Modern Cosmology

Every society has a story rooted in its most ancient traditions, of how the earth and sky originated. Most of these stories attribute the origin of all things to a Creator - whether God, Element or Idea. We first recall that in the Western world all discussions of the origin of the world were dominated until the 18th century by the story of Genesis, which describes the Creation as an ordered process that took seven days. Then we show how the development of mechanistic theories in the 18th century meant that the idea of an organized Creation gave way to the concept of evolution, helped by the fact that in the 19th century astrophysicists discovered that stars had their origin in clouds of gas. We conclude with Big bang theory, conceived at the beginning of the 20th century, that was subsequently developed into a more or less complete account of the history of the cosmos, from the supposed birth of space, time and matter out of the quantum vacuum until the emergence of life (at least on our planet Earth, and much probably elsewhere) and beyond.

physics.hist-ph↗

arXiv2016

The Holographic Universe

I give a critical review of the holographic hypothesis, which posits that a universe with gravity can be described by a quantum field theory in fewer dimensions. I first recall how the idea originated from considerations on black hole thermodynamics and the so-called information paradox that arises when Hawking radiation is taken into account. String Quantum Gravity tried to solve the puzzle using the AdS/CFT correspondence, according to which a black hole in a 5-D anti-de Sitter space is like a flat 4-D field of particles and radiation. Although such an interesting holographic property, also called gauge/gravity duality, has never been proved rigorously, it has impulsed a number of research programs in fields as diverse as nuclear physics, condensed matter physics, general relativity and cosmology. I finally discuss the pros and cons of the holographic conjecture, and emphasizes the key role played by black holes for understanding quantum gravity and possible dualities between distant fields of theoretical physics.

gr-qc↗

arXiv2016

The Status of Cosmic Topology after Planck Data

In the last decade, the study of the overall shape of the universe, called Cosmic Topology, has become testable by astronomical observations, especially the data from the Cosmic Microwave Background (hereafter CMB) obtained by WMAP and Planck telescopes. Cosmic Topology involves both global topological features and more local geometrical properties such as curvature. It deals with questions such as whether space is finite or infinite, simply-connected or multi-connected, and smaller or greater than its observable counterpart. A striking feature of some relativistic, multi-connected small universe models is to create multiples images of faraway cosmic sources. While the last CMB (Planck) data fit well the simplest model of a zero-curvature, infinite space model, they remain consistent with more complex shapes such as the spherical Poincare Dodecahedral Space, the flat hypertorus or the hyperbolic Picard horn. We review the theoretical and observational status of the field.

astro-ph.CO↗

arXiv2015

Lemaitre's Big Bang

I give an epistemological analysis of the developments of relativistic cosmology from 1917 to 1966, based on the seminal articles by Einstein, de Sitter, Friedmann, Lemaitre, Hubble, Gamow and other historical figures of the field. It appears that most of the ingredients of the present-day standard cosmological model, including the acceleration of the expansion due to a repulsive dark energy, the interpretation of the cosmological constant as vacuum energy or the possible non-trivial topology of space, had been anticipated by Georges Lemaitre, although his articles remain mostly unquoted.

physics.hist-ph↗

arXiv2015

The Warped Science of Interstellar

The science fiction film, Interstellar, tells the story of a team of astronauts searching a distant galaxy for habitable planets to colonize. Interstellar's story draws heavily from contemporary science. The film makes reference to a range of topics, from established concepts such as fast-spinning black holes, accretion disks, tidal effects, and time dilation, to far more speculative ideas such as wormholes, time travel, additional space dimensions, and the theory of everything. The aim of this article is to decipher some of the scientific notions which support the framework of the movie.

physics.pop-ph↗

arXiv2015

Willem Janszoon Blaeu

This article describes the life and work of Willem Janszoon Blaeu (1571-1638), who founded one of history's greatest cartographic publishing firms in 1599. Mostly renowned as a cartographer, he also made terrestrial and celestial globes, various instruments such as quadrants, a planetarium and a tellurium. He invented mechanical devices for improving the technics of printing. As an astronomer, a former student of Tycho Brahe, Willem Blaeu made careful observations of a moon eclipse, he discovered a variable star now known as P Cygni, and carried out a measurement of a degree on the surface of the earth (as his countryman Snell did in 1617).

physics.hist-ph↗

arXiv2015

Evry Leon Schatzman

This article describes the life and work of French astrophysicist Evry Schatzman (1920-2010). He was a pioneer in the study of white dwarfs during the 1940s and was one of the proponents of the wave heating theory of the solar corona. He made important contributions to the fields of internal stellar structure, novae, mechanisms of acceleration of cosmic rays, the role of turbulent diffusion in stellar evolution and its consequences for the lithium abundance, and the rate of solar neutrinos. Schatzman is mostly recognized as the creator of the French school of theoretical astrophysics. Although he was not the first theoretician of astrophysics in his country, he was the first to have felt the need for a rapid development of this subject in France, and the first to teach it and to guide the path of many young researchers. Many of them became involved, and some leaders, in space science.

physics.hist-ph↗

arXiv2013

Cosmic Topology : Twenty Years After

What is the shape of the Universe? Is it finite or infinite ? Is space multi-connected to create ghost images of faraway cosmic sources? After a "dark age" period, the field of cosmic topology has now become one of the major concerns in astronomy and cosmology, not only from theorists but also from observational astronomers. Here I give a personal account of the spectacular progress in the field since the beginning of the 1990's, when I started to work in it.

astro-ph.CO↗

arXiv2013

From Black Holes to Cosmology : The Universe in the Computer

I discuss some aspects of the use of computers in Relativity, Astrophysics and Cosmology. For each section I provide two examples representative of the field, including gravitational collapse, black hole imagery, supernovae explosions, star-black hole tidal interactions, N-body cosmological simulations and detection of cosmic topology.

astro-ph.IM↗

arXiv2013

Editorial note to "A Homogeneous Universe of Constant Mass and Increasing Radius accounting for the Radial Velocity of Extra--Galactic Nebulae" by Georges Lemaître (1927)

This is an editorial note to accompany printing as a Golden Oldie in the Journal of General Relativity and Gravitation of the fundamental article by Georges Lemaître first published in French in 1927, in which the author provided the first explanation of the observations on the recession velocities of galaxies as a natural consequence of dynamical cosmological solutions of Einstein's field equations, and discovered the so-called Hubble law. We analyze in detail the scientific contents of this outstanding work, we describe how it remained unread or poorly appreciated until 1930, and we list and explain the differences between the 1927 and 1931 versions. Indeed the English translation published in 1931 in MNRAS was not perfectly faithful to the original text - it was updated. As it turned out very recently, the updates were done by Lemaître himself, but the discrepancies between the two texts caused a temporary stir among historians. Our new translation - given in the Appendix - follows the 1927 version exactly.

physics.hist-ph↗