One-loop adjoint masses for branes at non-supersymmetric angles

This proceeding is based on arXiv:1105.0591 [hep-th] where we consider breaking of supersymmetry in intersecting D-brane configurations by slight deviation of the angles from their supersymmetric values. We compute the masses generated by radiative corrections for the adjoint scalars on the brane world-volumes. In the open string channel, the string two-point function receives contributions only from the infrared limits of N~4 and N~2 supersymmetric configurations, via messengers and their Kaluza-Klein excitations, and leads at leading order to tachyonic directions.Comment: 15 pages, 5 figures. Contribution to the proceedings of the Corfu Summer Institute 2011 School and Workshops on Elementary Particle Physics and Gravity, September 4-18 2011 Corfu, Greec

Conformal Field Theories in Fractional Dimensions

We study the conformal bootstrap in fractional space-time dimensions, obtaining rigorous bounds on operator dimensions. Our results show strong evidence that there is a family of unitary CFTs connecting the 2D Ising model, the 3D Ising model, and the free scalar theory in 4D. We give numerical predictions for the leading operator dimensions and central charge in this family at different values of D and compare these to calculations of phi^4 theory in the epsilon-expansion.Comment: 11 pages, 4 figures - references updated - one affiliation modifie

Fermion conformal bootstrap in 4d

We apply numerical conformal bootstrap techniques to the four-point function of a Weyl spinor in 4d non-supersymmetric CFTs. We find universal bounds on operator dimensions and OPE coefficients, including bounds on operators in mixed symmetry representations of the Lorentz group, which were inaccessible in previous bootstrap studies. We find discontinuities in some of the bounds on operator dimensions, and we show that they arise due to a generic yet previously unobserved fake primary effect, which is related to the existence of poles in conformal blocks. We show that this effect is also responsible for similar discontinuities found in four-fermion bootstrap in 3d, as well as in the mixed-correlator analysis of the 3d Ising CFT. As an important byproduct of our work, we develop a practical technology for numerical approximation of general 4d conformal blocks

Spin Excitations in a Fermi Gas of Atoms

We have experimentally investigated a spin excitation in a quantum degenerate Fermi gas of atoms. In the hydrodynamic regime the damping time of the collective excitation is used to probe the quantum behavior of the gas. At temperatures below the Fermi temperature we measure up to a factor of 2 reduction in the excitation damping time. In addition we observe a strong excitation energy dependence for this quantum statistical effect.Comment: 4 pages, 3 figure

NW Adriatic Sea variability in relation to chlorophyll-<I>a</I> dynamics in the last 20 years (1986?2005)

International audienceThis paper presents a long-term time series (1986?2005) of hydrological and biogeochemical data, both published and unpublished. Data were collected in the north-western area of the Adriatic Sea, at two stations that are considered hydrodynamically and trophically different. The time series have been statistically and graphically investigated on a monthly scale in order to find not only possible chlorophyll-a trends over time, but also links between the concentrations of chlorophyll-a and the variability in the environment, as well as trophic differences between the two areas. Basically, in both cases the statistical test results show no significant trends in either the average chlorophyll-a values or in dispersion of the data, in contrast with significant trends in temperature and salinity. The two areas have similar hydrological features, yet they present significant differences in the amount of nutrient inputs: these are in fact higher at the coastal site, which is characterized by a prevalence of surface blooms, while they are lower at the offshore station, which is mainly affected by intermediate blooms. Nonetheless, throughout the whole water column, chlorophyll-a concentrations are only slightly different. Both areas are affected by riverine discharge, though in the first case considered chlorophyll-a concentrations are also driven strongly by the seasonal cycle. Finally, the results show that the two stations are not trophically different, although some controlling factors, such as zooplankton grazing in one case and light attenuation in the other, may regulate the growth of phytoplankton

NW Adriatic Sea biogeochemical variability in the last 20 years (1986–2005)

International audience; This paper presents a long-term time series (1986?2005) of hydrological and biogeochemical data, both published and unpublished. Data were collected in the north-western area of the Adriatic Sea, at two stations that are considered hydrodynamically and trophically different. The time series have been statistically and graphically analysed on a monthly scale in order to study the annual climatologies, links between the concentrations of chlorophyll-a and the variability in the environment, trophic differences between the two areas and chlorophyll-a trends over time. Basically, the two areas have similar hydrological features, yet they present significant differences in the amount of nutrient inputs: these are in fact higher at the coastal site, which is characterized by a prevalence of surface blooms, while they are lower at the offshore station, which is mainly affected by blooms at intermediate depths. Nonetheless, throughout the whole water column, chlorophyll-a concentrations are only slightly different. Both areas are affected by riverine discharge, though chlorophyll-a concentrations are also driven strongly by the seasonal cycle at the station closer to the coast. Results show that the two stations are not trophically different, although some controlling factors, such as zooplankton grazing in one case and light attenuation in the other, may further regulate the growth of phytoplankton. In both cases no significant trends are detected in either the average chlorophyll-a values or in dispersion of the data, in contrast with significant trends in temperature and salinity

Finite temperature hydrodynamic modes of trapped quantum gases

The hydrodynamic equations of an ideal fluid formed by a dilute quantum gas in a parabolic trapping potential are studied analytically and numerically. Due to the appearance of internal modes in the fluid stratified by the trapping potential, the spectrum of low-lying modes is found to be dense in the high-temperature limit, with an infinitely degenerate set of zero-frequency modes. The spectrum for Bose-fluids and Fermi-fluids is obtained and discussed.Comment: 26 pages, Late

Carving out OPE space and precise O(2) model critical exponents

We develop new tools for isolating CFTs using the numerical bootstrap. A “cutting surface” algorithm for scanning OPE coefficients makes it possible to find islands in high-dimensional spaces. Together with recent progress in large-scale semidefinite programming, this enables bootstrap studies of much larger systems of correlation functions than was previously practical. We apply these methods to correlation functions of charge-0, 1, and 2 scalars in the 3d O(2) model, computing new precise values for scaling dimensions and OPE coefficients in this theory. Our new determinations of scaling dimensions are consistent with and improve upon existing Monte Carlo simulations, sharpening the existing decades-old 8σ discrepancy between theory and experiment

Collisionless collective modes of fermions in magnetic traps

We present a Random-Phase-Approximation formalism for the collective spectrum of two hyperfine species of dilute 40K atoms, magnetically trapped at zero temperature and subjected to a repulsive s-wave interaction between atoms with different spin projections. We examine the density-like and the spin-like oscillation spectra, as well as the transition density profiles created by external multipolar fields. The zero sound spectrum is always fragmented and the density and spin channels become clearly distinguishable if the trapping potentials acting on the species are identical. Although this distinction is lost when these confining fields are different, at selected excitation frequencies the transition densities may display the signature of the channel.Comment: 10 pages, 9 figure

Translucent zirconia in the ceramic scenario for monolithic restorations: A flexural strength and translucency comparison test

Objective: To compare three different compositions of Yttria-Tetragonal Zirconia Polycrystal (Y-TZP) ceramic and a lithium disilicate ceramic in terms of flexural strength and translucency. Methods: Three zirconia materials of different composition and translucency, Aadva ST [ST], Aadva EI [EI] and Aadva NT [NT](GC Tech, Leuven, Belgium) were cut with a slow speed diamond saw into beams and tabs in order to obtain, after sintering, dimensions of 1.2 × 4.0 × 15.0 mm and 15.0 × 15.0 × 1.0 mm respectively. Blocks of IPS e.max CAD LT were cut and crystallized in the same shapes and dimensions and used as a reference group [LD]. Beams (n = 15) were tested in a universal testing machine for three-point bending strength. Critical fracture load was recorded in N, flexural strength (σ in MPa), Weibull modulus (m) and Weibull characteristic strength (σ0 in MPa) were then calculated. Tabs (n = 10) were measured with a spectrophotometer equipped with an integrating sphere. Contrast Ratios were calculated as CR = Yb/Yw. SEM of thermally etched samples coupled with lineal line analysis (n = 6) was used to measure the tested zirconia grain size. Data were statistically analyzed. Results: Differences in translucency, flexural strength and grain size were found to be statistically significant. CR increased and flexural strength decreased in the following order ST(σ 1215 ± 190 MPa, CR 0.74 ± 0.01) &gt; EI(σ 983 ± 182 MPa, CR 0.69 ± 0.01) &gt; NT(σ 539 ± 66 MPa, CR 0.65 ± 0.01) &gt; LD (σ 377 ± 39 Mpa, CR 0.56 ± 0.02). The average grain size was different for the three zirconia samples with NT(558 ± 38 nm) &gt; ST(445 ± 34 nm) &gt; EI(284 ± 11 nm). Conclusions: The zirconia composition heavily influenced both the flexural strength and the translucency. Different percentages of Yittria and Alumina result in new materials with intermediate properties in between the conventional zirconia and lithium disilicate. Clinical indications for Zirconia Aadva NT should be limited up to three-unit span bridges