Proofs, Reasoning and the Metamorphosis of Logic

Revised version of a conference given under title "From Natural Deduction to the nature of reasoning", at the colloquium Natural Deduction organized by Luiz Carlos Pereira and dedicated to the work of Dag Prawitz, Rio de Janeiro, Brazil, July 2001.With the “mathematical watershed”, Logic had been transformed into a foundational theory for mathematics, a theory of truth and proofs - far away from its philosophical status of theory of the intellectual process of reasoning. With the recent substitution of the traditional proofs-as-discourses paradigm by the proofs-as-programs one, Logic is now becomming a foundational theory for computing. One could interpret this new watershed as being “yet another technological drift”, bringing Logic always closer to applied ingeneering, always further from the human intellectual process of reasoning. This article promote the dual point of view: enlightened by the contemporary analysis of the dynamic of proofs, which bring us to a new understanding of the semantic counterpart of processes operationality (including the links between semantic dereliction due to inconsistency and computational exuberance), Logic has never appeared so close to being, finally, the theory of reasoning.A partir de son "tournant mathématique", la logique se convertit en une théorie des fondements des mathématiques, une théorie de la vérité et des preuves - loin de son statut philosophique de theorie du processus intellectuel de raisonnement. Avec le remplacement récent du paradigme traditionnel des preuves-comme-discours par celui des preuves-comme-programes, la Logique est à présent devenue une théorie des fondements du calcul. On peut voir dans ce nouveau tournant comme un glissement supplémentaire qui conduirait la logique toujours plus près de l'ingénierie appliquée, toujours plus loin de son statut historique de théorie des processus de raisonnement. Cet article défend le point de vue dual: sous la lumière des analyses contemporaines de la dynamique des preuves, qui conduisent à une compréhension originale de la contrepartie sémantique de l'opérationalité des processus (y compris les liens entre déreliction sémantique due à l'incohérence et exubérance calculatoire), la logique n'a finalement jamais semblé aussi proche de devenir la théorie du raisonnement

Nature et logique, de G. Gentzen à J-Y. Girard

Version ancienne d'un article dont la version modifiée a finalement été acceptée pour publication en 2014 dans Logique et AnalyseJ.-Y. Girard's conception of logic originates in the critique of logical naturality made by G. Gentzen around 1930. Recently, Girard radicalized this critique and proposed a program for new foundations for logic, as a product of a general theory of interaction. The present paper is an attempt to show that this program tends to reunify the idea of natural logic and the idea of a logic of nature.La conception de la logique de J.-Y. Girard s'enracine dans la critique de la naturalité logique opérée par G. Gentzen dans les années 1930. Récemment, Girard a radicalisé cette critique et proposé une entreprise de refondation de la logique comme produit d'une théorie générale de l'interaction. La présente étude vise à montrer que cette entreprise va dans le sens d'une réunification de l'idée de logique naturelle et de celle de logique de la nature

Hard X-ray emission of the microquasar GRO J1655-40 during the rise of its 2005 outburst

We present the analysis of the high energy emission of the Galactic black hole GRO J1655-40 at the beginning of its 2005 outburst. The data from 458 ks of INTEGRAL observations, spread over 4 weeks, are analyzed, along with the existing simultaneous RXTE and Swift data. The high energy data allow us to detect the presence of a high energy cut-off and to study its evolution during the outburst rise. This high energy feature is generally related to thermal mechanisms in the framework of Comptonization models from which we can estimate the plasma parameters. We found an electron temperature of about 30-40 keV and an optical depth around 1.8-2.1. The high energy cut-off decreased along with the radio flux, and disappeared as the jet turned off.Comment: 24 pages, 5 figures, accepted for publication in the Astrophsical Journa

Suzaku Observations of the Galactic Center Microquasar 1E 1740.7-2942

We present two Suzaku observations of the Galactic center microquasar 1E 1740.7-2942 separated by approximately 700 days. The source was observed on both occasions after a transition to the spectrally hard state. Significant emission from 1E 1740.7-2942 is detected out to an energy of 300 keV, with no spectral break or turnover evident in the data. We tentatively measure a lower limit to the cut-off energy of ~ 380 keV. The spectra are found to be consistent with a Comptonized corona on both occasions, where the high energy emission is consistent with a hard power-law (\Gamma ~ 1.8) with a significant contribution from an accretion disc with a temperature of ~ 0.4 keV at soft X-ray energies. The measured value for the inner radius of the accretion disc is found to be inconsistent with the picture whereby the disc is truncated at large radii in the low-hard state and instead favours a radius close to the ISCO (R_in ~ 10 - 20 R_g).Comment: 8 pages, 4 figures, formatted using emulateapj.cls. Accepted for publication in Ap

Modeling the hard states of three black hole candidates

Simultaneous multiwavelength observations were recently performed for three black hole candidates --- SWIFT J1753.5-0127, GRO J1655-40 and XTE J1720-318. In this paper we test the accretion-jet model originally proposed to XTE J1118+480 by investigating the hard state of these three sources using this model. The accretion flow in the model is composed of an inner hot accretion flow and an outer truncated thin disk. We find that the model satisfactorily explains the spectrum ranging from radio to X-rays, with the radio and X-ray spectra dominated by the synchrotron and thermal Comptonization emissions in the jet and the hot accretion flow respectively, while the infrared and optical being the sum of the emissions from the jet, hot accretion flow, and the truncated thin disk. Similar to the case of XTE J1118+480, the model can also explain, although only qualitatively in some cases, the observed timing features including QPO, and positive and negative time lags between the optical and X-ray emissions detected in SWIFT J1753.5-0127. The origin of the ejection events detected in XTE J1720-318 is also briefly discussed.Comment: 7 pages, 6 figures accepted for publication in ApJ, minor modification after proo

Studies of release properties of ISOLDE targets

Off-line release rates of Be, Mg, S, Mn and Kr from refractory materials were studied. Mn yields were determined from a ZrO2 target and Kr yields from a SrO and ZrO2 targets. A Monte Carlo code to optimize ISOLDE targets was introduced

X-ray spectral state evolution in IGR J17091-3624 and comparison of its heartbeat oscillation properties with those of GRS 1915+105

In this work, we study the X-ray timing and spectral evolution of the transient low mass X-ray binary IGR J17091-3624 during first 66 days of its 2011 outburst. We present results obtained from observations with two instruments, Rossi X-ray Timing Explorer (RXTE)/Proportional Counter Array (PCA) and SWIFT/X-ray telescope (XRT), between 09 February, 2011 and 15 April, 2011. Using quasi-periodic oscillation classifications, power density spectrum characteristics, time-lag behavior and energy spectral properties, we determine source states and their transitions at different times of the outburst. During the first part of the evolution, the source followed trends usually observed from transient black hole X-ray binaries (BHXBs). Interestingly, a gradual transition is observed in IGR J17091-3624 from the low-variability SIMS, commonly seen in BHXBs, to a high-variability state with regular, repetitive and structured pulsations, seen only from GRS 1915+105 (also known as 'rho' class variability/'heartbeat' oscillations). We study the time evolution of characteristic time-scale, quality factor and rms amplitude of heartbeat oscillations in IGR J17091-3624. We also present a detailed comparison of the timing and spectral properties of heartbeat oscillations and their evolution in IGR J17091-3624 and GRS 1915+105.Comment: 23 pages, 10 figures, 3 tables, accepted for publication in the Ap

3-200 keV spectral states and variability of the INTEGRAL Black Hole binary IGR J17464-3213

On March 2003, IBIS, the gamma-ray imager on board the INTEGRAL satellite, detected an outburst from a new source, IGR J17464-3213, that turned out to be a HEAO-1 transient, H1743-322. In this paper we report on the high energy behaviour of this BHC studied with the three main instruments onboard INTEGRAL. The data, collected with unprecedented sensitivity in the hard X-Ray range, show a quite hard Comptonised emission from 3 keV up to 150 keV during the rising part of the source outburst, with no thermal emission detectable. A few days later, a prominent soft disk multicolour component appears, with the hard tail luminosity almost unchanged: 10-9 erg*cm-2*s-1. Two months later, during a second monitoring campaign near the end of the outburst, the observed disk component was unchanged. Conversely, the Comptonised emission from the central-hot part of the disk reduced by a factor of 10. We present here its long term behaviour in different energy ranges and the combined JEM-X, SPI and IBIS wide band spectral evolution of this source.Comment: 12 pages, 4 figures, accepted for pubblication in AP