Universality of One-Dimensional Fermi Systems,I. Response Functions and Critical Exponents

The critical behavior of one-dimensional interacting Fermi systems is expected to display universality features, called Luttinger liquid behavior. Critical exponents and certain thermodynamic quantities are expected to be related among each other by model-independent formulas. We establish such relations, the proof of which has represented a challenging mathematical problem, for a general model of spinning fermions on a one dimensional lattice; interactions are short ranged and satisfy a positivity condition which makes the model critical at zero temperature. Proofs are reported in two papers: in the present one, we demonstrate that the zero temperature response functions in the thermodynamic limit are Borel summable and have anomalous power-law decay with multiplicative logarithmic corrections. Critical exponents are expressed in terms of convergent expansions and depend on all the model details. All results are valid for the special case of the Hubbard model.     

Ultrafast all‐optical order‐to‐chaos transition in silicon photonic crystal chips

The interaction of light with nanostructured materials provides exciting new opportunities for investigating classical wave analogies of quantum phenomena. A topic of particular interest forms the interplay between wave physics and chaos in systems where a small perturbation can drive the behavior from the classical to chaotic regime. Here, we report an all‐optical laser‐driven transition from order to chaos in integrated chips on a silicon photonics platform. A square photonic crystal microcavity at telecom wavelengths is tuned from an ordered into a chaotic regime through a perturbation induced by ultrafast laser pulses in the ultraviolet range. The chaotic dynamics of weak probe pulses in the near infrared is characterized for different pump‐probe delay times and at various positions in the cavity, with high spatial accuracy. Our experimental analysis, confirmed by numerical modelling based on random matrices, demonstrates that nonlinear optics can be used to control reversibly the chaotic behavior of light in optical resonators.

     

Evidence for the production of thermal muon pairs with masses above 1 GeV/c 2 in 158 A GeV indium-indium collisions

The yield of muon pairs in the invariant mass region 1<M<2.5 GeV/c ² produced in heavy-ion collisions significantly exceeds the sum of the two expected contributions, Drell-Yan dimuons and muon pairs from the decays of D meson pairs. These sources properly account for the dimuons produced in proton-nucleus collisions. In this paper, we show that dimuons are also produced in excess in 158 A GeV In-In collisions. We furthermore observe, by tagging the dimuon vertices, that this excess is not due to enhanced D meson production, but made of prompt muon pairs, as expected from a source of thermal dimuons specific to high-energy nucleus-nucleus collisions. The yield of this excess increases significantly from peripheral to central collisions, both with respect to the Drell-Yan yield and to the number of nucleons participating in the collisions. Furthermore, the transverse mass distributions of the excess dimuons are well described by an exponential function, with inverse slope values around 190 MeV. The values are independent of mass and significantly lower than those found at masses below 1 GeV/c ², rising there up to 250 MeV due to radial flow. This suggests the emission source of thermal dimuons above 1 GeV/c ² to be of largely partonic origin, when radial flow has not yet built up.     

Photonic crystal slotted slab waveguides

We report on the fabrication of photonic crystal waveguides in SOI that comprise an air-slot in the centre. The slot serves to confine suitably polarised optical radiation (H-polarisation) and due to its small size, provides extremely high field intensity values out with the high index material. Adding the photonic crystal environment then provides full control over the dispersive properties of this waveguide. We demonstrate the successful operation of this structure experimentally and explain its key features.     

Functional Integral Construction of the Massive Thirring model: Verification of Axioms and Massless Limit

We present a complete construction of a Quantum Field Theory for the Massive Thirring model by following a functional integral approach. This is done by introducing an ultraviolet and an infrared cutoff and by proving that, if the “bare” parameters are suitably chosen, the Schwinger functions have a well defined limit satisfying the Osterwalder-Schrader axioms, when the cutoffs are removed. Our results, which are restricted to weak coupling, are uniform in the value of the mass. The control of the effective coupling (which is the main ingredient of the proof) is achieved by using the Ward Identities of the massless model, in the approximated form they take in the presence of the cutoffs. As a byproduct, we show that, when the cutoffs are removed, theWard Identities have anomalies which are not linear in the bare coupling. Moreover, we find for the interacting propagator of the massless theory a closed equation which is different from that usually stated in the physical literature.     

Crosslinking Allosteric Sites on the Nucleosome

Targeting defined histone protein sites in chromatin is an emerging therapeutic approach that can potentially be enhanced by allosteric effects within the nucleosome. Here we characterized a novel hetero‐bimetallic compound with a design based on a nucleosomal allostery effect observed earlier for two unrelated drugs—the Ru^II antimetastasis/antitumor RAPTA‐T and the Au^I anti‐arthritic auranofin. The Ru^II moiety binds specifically to two H2A glutamate residues on the nucleosome acidic patch, allosterically triggering a cascade of structural changes that promote binding of the Au^I moiety to selective histidine residues on H3, resulting in cross‐linking sites that are over 35 Å distant. By tethering the H2A‐H2B dimers to the H3‐H4 tetramer, the hetero‐bimetallic compound significantly increases stability of the nucleosome, illustrating its utility as a site‐selective cross‐linking agent.     

Molecular Kondo resonance in atomic Fermi gases

The usual Kondo effect is associated with the formation of a many-body ground state that contains a quantum-mechanical entanglement between a (localized) fermion and the free fermions. We show, however, that also a bosonic form of the Kondo effect can occur in degenerate atomic Fermi gases near a Feshbach resonance, if the energy of the diatomic molecular level associated with the Feshbach resonance approaches twice the Fermi energy of the atoms.     

Preconcentration and dansylation of aliphatic amines using C18 solid-phase packings. Application to the screening analysis in environmental water samples

Precolumn preconcentration and derivatization on solid sorbents (Bond Elut C18 solid-phase extraction cartridges) of low-molecular-mass aliphatic amines in water samples have been performed using dansyl chloride (Dns-Cl) as derivatization reagent. Conditions for analyte preconcentration and derivatization such as volume sample, reagent concentration, time, pH and temperature reaction were optimised. On the basis of these studies a rapid and sensitive method for screening of aliphatic amines in waters is presented. Up to volumes of 5 ml, samples are drawn through the sorbent, the analytes retained are dansylated at basic pH, at 100 degrees C for 10 min or 85 degrees C for 15 min. The derivatized analytes are desorbed with 0.5 ml of acetonitrile. Twenty microl of the collected extracts are chromatographed in a Hypersyl ODS C18 column using an acetonitrile-imidazole (pH 7) gradient for elution. Seven amines and ammonium were separated within 9 min. The Dns derivatives were monitored at 333 nm with UV detection and at lambda(excitation) = 350 nm and lambda(emission) = 530 nm with fluorescence detection. The different signals are compared. Dynamic ranges from 10 to 250 microg/l and limits of detection at the microgram-per-litre level and relative standard deviations from 2 to 15% were obtained for all the amines. The total analysis time (sample treatment plus chromatography) was less than 25 min. The method was applied to determination and screening analysis of these analytes in real environmental water samples.