Republique et citoyennete a l'aube du second siecle. Une certaine idée de la république chez Pline le Jeune

De nombreux auteurs dont Th.Mommsen, E. Allain, C. E. Pulciano et F. Trisoglio et J. Gaudemet ont relevé l'esprit profondément humaniste qui animait Pline le Jeune et qui se traduit par ses donations, son aide et son soutien auprès de jeunes gens de sa cité de Côme mais aussi par son inquiétude d'une répression trop sévère à l'égard des chrétiens de Pont et Bithynie. Son souci à l'égard des esclaves et des affranchis témoigne également, chez ce disciple lointain de Cicéron (P. Dragicevic), d'un intérêt accru pour la “question sociale” et pour le développement en taille et en sagesse de la Cité. C'est ainsi que Pline envisage sous deux aspects qui paraissent profondément contradictoires un idéal dont l'idée démocratique n'est pas absente: non seulement les citoyens doivent être nombreux mais ils doivent jouir de la libertas, de la securitas et respecter un «état de droit» en ne bousculant pas les bonnes traditions acquises. Les membres de la Cité idéale de Pline participent certes à la grandeur de l'Urbs de par leurs activités et leur confiance en César mais n'ont pas à modifier le régime parfait et harmonieux que semble dorénavant incarner le Prince. Il n'y a donc plus de place pour la démagogie car «le nombre ne peut avoir raison du poids des sentences, de la justesse des votes... de la qualité des avis.» Dès lors, l'opinion de Pline est le reflet de la nouvelle mentalité «antonine» au début du Second siècle ; elle préfigure la conception latine généreuse mais réduite de la ciuitas du Bas-Empire.Numerosos autores de los cuales Th. Mommsen, E. A1llain, S. E. Pulciano, F. Trisolgio y J. Gaudemet han alzado el espiritù profondamento humanisme que anima Plinio le Joven y que se traduce por sus donaciones su ayuda y su sosten hacia juvenes de su ciudad de Como pero tambien por su proccupacion de una represion demasiada dura hacia los Cristianos de Ponto y Bitinia. Su cuidado en consideracion a los esclavos y los emancipados testiga de la misma manera por este lejano discipulo de Tullius Cicero (Padre Dragicevic) de un interes mas importante por la cuestion sociale y por el desarrollamiento en estatura e en sabiduria de la ciudad. Asi es que Plinio ve dos aspectos que aparecen profundamente contradictorios un ideal cuya idea democratica n o es ausente : non solo los ciudadanos no deben estar numerosos pero deben gozar de la libertas de la securitas y respectar un «estado de derecho» sin trastonar las buenas tradiciones recibidas . Los membros de la ciudad ideal de Plinio participan desde luego al prestigio del Urbs con sus actividades y su confianza en Caesar pero no han que cambiar el regimen perfecto e armonioso que parece desde ahora encarnar el Principe. No hay desde luego sitio por la demagogia: pues, «el nombre no puede tener razon del peso de las semillas, de la rectidud de los votos… de la calidad de los avisos. » Asi, la opinion de Plinio es el reflecto de la nueva mentalidad «antoniana» al principio del segundo siglo ; prefigura la concepcion latina generosa pero recta de la ciudad del Bajo Empiro

Momentum-space structure of quasielastic spin fluctuations in Ce3Pd20Si6

Among heavy-fermion metals, Ce$_3$Pd$_{20}$Si$_6$ is one of the heaviest-electron systems known to date. Here we used high-resolution neutron spectroscopy to observe low-energy magnetic scattering from a single crystal of this compound in the paramagnetic state. We investigated its temperature dependence and distribution in momentum space, which was not accessible in earlier measurements on polycrystalline samples. At low temperatures, a quasielastic magnetic response with a half-width {\Gamma}=0.1 meV persists with varying intensity all over the Brillouin zone. It forms a broad hump centered at the (111) scattering vector, surrounded by minima of intensity at (002), (220) and equivalent wave vectors. The momentum-space structure distinguishes this signal from a simple crystal-field excitation at 0.31 meV, suggested previously, and rather lets us ascribe it to short-range dynamical correlations between the neighboring Ce ions, mediated by the itinerant heavy f-electrons via the RKKY mechanism. With increasing temperature, the energy width of the signal follows the conventional T$\scriptstyle^{1/2}$ law, {\Gamma}(T) = {\Gamma}$_0$ + A*T$\scriptstyle^{1/2}$. The momentum-space symmetry of the quasielastic response suggests that it stems from the simple-cubic Ce sublattice occupying the 8c Wyckoff site, whereas the crystallographically inequivalent 4a site remains magnetically silent in this material.Comment: 5 pages, 4 figure

Evidence for short-range antiferromagnetic fluctuations in Kondo-insulating YbB12

The spin dynamics of mixed-valence YbB12 has been studied by inelastic neutron scattering on a high-quality single crystal. In the Kondo-insulating regime realized at low temperature, the spectra exhibit a spin-gap structure with two sharp, dispersive, in-gap excitations at E = 14.5 and approximately 20 meV. The lower mode is shown to be associated with short-range correlations near the antiferromagnetic wave vector q0 = (1/2, 1/2, 1/2). Its properties are in overall agreement with those expected for a "spin exciton'' branch in an indirect hybridization gap semiconductor.Comment: 4 pages, 4 figures ; submitted to Physical Review Letter

Pressure Evolution of the Magnetic Field induced Ferromagnetic Fluctuation through the Pseudo-Metamagnetism of CeRu2Si2

Resistivity measurements performed under pressure in the paramagnetic ground state of CeRu2Si2 are reported. They demonstrate that the relative change of effective mass through the pseudo metamagnetic transition is invariant under pressure. The results are compared with the first order metamagnetic transition due to the antiferromagnetism of Ce0.9La0.1Ru2Si2 which corresponds to the "negative" pressure of CeRu2Si2 by volume expansion. Finally, we describe the link between the spin-depairing of quasiparticles on CeRu2Si2 and that of Cooper pairs on the unconventional heavy fermion superconductor CeCoIn5.Comment: 5 pages, 6 figures, accepted for publication in J. Phys. Soc. Jp

The effect of uniaxial pressure on the magnetic anomalies of the heavy-fermion metamagnet CeRu2Si2

The effect of uniaxial pressure (P_u) on the magnetic susceptibility (X), magnetization (M), and magnetoresistance (MR) of the heavy-fermion metamagnet CeRu2Si2 has been investigated. For the magnetic field along the tetragonal c axis, it is found that characteristic physical quantities, i.e., the temperature of the susceptibility maximum (T_max), the pagamagnetic Weiss temperature (Q_p), 1/X at 2 K, and the magnetic field of the metamagnetic anomaly (H_M), scale approximately linearly with P_u, indicating that all the quantities are related to the same energy scale, probably of the Kondo temperature. The increase (decrease) of the quantities for P_u || c axis (P_u || a axis) can be attributed to a decrease (increase) in the nearest Ce-Ru distance. Consistently in MR and X, we observed a sign that the anisotropic nature of the hybridization, which is believed to play an important role in the metamagnetic anomaly, can be controlled by applying the uniaxial pressure. PACS numbers: 75.20.Hr, 71.27.+a, 74.62.FjComment: 7 pages, ReVTeX, 6 EPS figures : Will appear in Phys. Rev.

Spontaneous deformation of the Fermi surface due to strong correlation in the two-dimensional t-J model

Fermi surface of the two-dimensional t-J model is studied using the variational Monte Carlo method. We study the Gutzwiller projected d-wave superconducting state with an additional variational parameter t'_v corresponding to the next-nearest neighbor hopping term. It is found that the finite t'_v<0 gives the lowest variational energy in the wide range of hole-doping rates. The obtained momentum distribution function shows that the Fermi surface deforms spontaneously. It is also shown that the van Hove singularity is always located very close to the Fermi energy. Using the Gutzwiller approximation, we show that this spontaneous deformation is due to the Gutzwiller projection operator or the strong correlation.Comment: 4 pages, 3 eps figures, revte