Thermal one- and two-graviton Green's functions in the temporal gauge

The thermal one- and two-graviton Green's function are computed using a temporal gauge. In order to handle the extra poles which are present in the propagator, we employ an ambiguity-free technique in the imaginary-time formalism. For temperatures T high compared with the external momentum, we obtain the leading T^4 as well as the subleading T^2 and log(T) contributions to the graviton self-energy. The gauge fixing independence of the leading T^4 terms as well as the Ward identity relating the self-energy with the one-point function are explicitly verified. We also verify the 't Hooft identities for the subleading T^2 terms and show that the logarithmic part has the same structure as the residue of the ultraviolet pole of the zero temperature graviton self-energy. We explicitly compute the extra terms generated by the prescription poles and verify that they do not change the behavior of the leading and sub-leading contributions from the hard thermal loop region. We discuss the modification of the solutions of the dispersion relations in the graviton plasma induced by the subleading T^2 contributions.Comment: 17 pages, 5 figures. Revised version to be published in Phys. Rev.

S-wave Kpi scattering in chiral perturbation theory with resonances

We present a detailed analysis of S-wave Kpi scattering up to 2 GeV, making use of the resonance chiral Lagrangian predictions together with a suitable unitarisation method. Our approach incorporates known theoretical constraints at low and high energies. The present experimental status, with partly conflicting data from different experiments, is discussed. Our analysis allows to resolve some experimental ambiguities, but better data are needed in order to determine the cross-section in the higher-energy range. Our best fits are used to determine the masses and widths of the relevant scalar resonances in this energy region.Comment: 40 pages, 6 figure

Experimental evidence for a light and broad scalar resonance in D+→π−π+π+D^+\to \pi^-\pi^+\pi^+ decay

From a sample of $1172 \pm 61$ $D^+ \to \pi^- \pi^+ \pi^+$ decay, we find $\Gamma (D^+ \to \pi^- \pi^+ \pi^+) / \Gamma (D^+ \to K^- \pi^+ \pi^+) = 0.0311 \pm 0.0018 ^{+0.0016}_{-0.0026}$. Using a coherent amplitude analysis to fit the Dalitz plot of this decays, we find strong evidence that a scalar resonance of mass $478^{+24}_{-23} \pm 17$ MeV/$c^2$ and width $324^{+42}_{-40} \pm 21$ MeV/$c^2$ accounts for approximately half of all decays.Comment: 10 pages, 3 eps figure

Dalitz Plot Analysis of the Decay D^+ --> K^- pi^+ pi^+ and Indication of a Low-Mass Scalar K pi Resonance

We study the Dalitz plot of the decay D^+ --> K^- pi^+ pi^+ with a sample of 15090 events from Fermilab experiment E791. Modeling the decay amplitude as the coherent sum of known K pi resonances and a uniform nonresonant term, we do not obtain an acceptable fit. If we allow the mass and width of the K^*_0(1430) to float, we obtain values consistent with those from PDG but the chi^2 per degree of freedom of the fit is still unsatisfactory. A good fit is found when we allow for the presence of an additional scalar resonance, with mass 797 +/- 19 +/- 43 MeV/c^2 and width 410 +/- 43 +/- 87 MeV/c^2. The mass and width of the K^*_0(1430) become 1459 +/- 7 +/- 5 MeV/c^2 and 175 +/- 12 +/- 12 MeV/c^2, respectively. Our results provide new information on the scalar sector in hadron spectroscopy.Comment: Accepted for publication in Physical Review Letter

‘Exceeding the Age in Every Thing’: Placing Sloane’s Objects

That objects of knowledge get moved across boundaries is well known. But how they get moved often goes unexamined. Modes of movement cannot be ignored when considering objects’ historical signi?cance. Put differently, how geographies are negotiated is central to the constitution of knowledge objects. This essay offers a brief assessment of the competing agencies at work in the global collections of the Enlightenment naturalist Sir Hans Sloane (1660–1753). While discussing broadly the relationship between collecting and power in Sloane’s career, the essay stresses the passivity and strategic weakness of the collector, and suggests how the meanings of speci?c curiosities varied according to asymmetries in their mode of transfer

« Very much in the dark about light » : Franklin, lumières et critiques

Cet essai considère une critique des expériences électriques de Benjamin Franklin, publiée anonymement à Londres en 1777. L'auteur s'interroge pour savoir s'il est légitime de regarder ces expériences comme « natural philosophy » dans la tradition d’Isaac Newton. Cette critique des lumières frankliniennes est considérée en connection avec les conflits de la Révolution américaine, les angoisses sociales sur la dextérité mécanique, et la hiérarchie géographique des savoirs. Les débats sur le caractère de la vraie philosophie naturelle qui touchaient les expériences de Franklin portaient également sur la constitution sociale, politique et géographique de l’autorité.<br>This essay discusses a critical account of Benjamin Franklin’s experiments with electricity published anonymously in London in 1777. The fundamental question raised was whether Franklin’s famous experiments constituted legitimate natural philosophy in the tradition of Isaac Newton. This dim view of Franklinist enlightenment is linked to the conflicts of the American Revolution, social anxieties about mechanical ingenuity, and geographical hierarchies of knowledge-making. It is argued that debates over the legitimacy of the proper character of natural philosophy that addressed Franklinist science were also debates over the social, political and geographical constitution of authority