Non-reciprocal few-photon devices based on chiral waveguide-emitter couplings

We demonstrate the possibility of designing efficient, non reciprocal few-photon devices by exploiting the chiral coupling between two waveguide modes and a single quantum emitter. We show how this system can induce non-reciprocal photon transport at the single-photon level and act as an optical diode. Afterwards, we also show how the same system shows a transistor-like behaviour for a two-photon input. The efficiency in both cases is shown to be large for feasible experimental implementations. Our results illustrate the potential of chiral waveguide-emitter couplings for applications in quantum circuitry.Comment: Mathematica notebook attached for calculation of detection probabilitie

Quantum Decoherence of Photons in the Presence of Hidden U(1)s

Many extensions of the standard model predict the existence of hidden sectors that may contain unbroken abelian gauge groups. We argue that in the presence of quantum decoherence photons may convert into hidden photons on sufficiently long time scales and show that this effect is strongly constrained by CMB and supernova data. In particular, Planck-scale suppressed decoherence scales D ~ E^2/M_Pl (characteristic for non-critical string theories) are incompatible with the presence of even a single hidden U(1). The corresponding bounds on the decoherence scale are four orders of magnitude stronger than analogous bounds derived from solar and reactor neutrino data and complement other bounds derived from atmospheric neutrino data.Comment: 8 pages, 9 figure

Line-of-sight velocity distributions of elliptical galaxies from collisionless mergers

We analyse the skewness of the line-of-sight velocity distributions in model elliptical galaxies built through collisionless galaxy mergers. We build the models using large N-body simulations of mergers between either two spiral or two elliptical galaxies. Our aim is to investigate whether the observed ranges of skewness coefficient (h3) and the rotational support (V/sigma), as well as the anticorrelation between h3 and V, may be reproduced through collisionless mergers. Previous attempts using N-body simulations failed to reach V/sigma ~ 1-2 and corresponding high h3 values, which suggested that gas dynamics and ensuing star formation might be needed in order to explain the skewness properties of ellipticals through mergers. Here we show that high V/sigma and high h3 are reproduced in collisionless spiral-spiral mergers whenever a central bulge allows the discs to retain some of their original angular momentum during the merger. We also show that elliptical-elliptical mergers, unless merging from a high-angular momentum orbit, reproduce the strong skewness observed in non-rotating, giant, boxy ellipticals. The behaviour of the h3 coefficient therefore associates rapidly-rotating disky ellipticals to disc-disc mergers, and associates boxy, slowly-rotating giant ellipticals to elliptical-elliptical mergers, a framework generally consistent with the expectations of hierarchical galaxy formation.Comment: 5 pages, 4 figures, MNRAS Letters, in pres

Recent results on self-dual configurations on the torus

We review the recent progress on our understanding of self-dual SU(N) Yang-Mills configurations on the torus.Comment: Latex 3 pages, 1 figure. Contribution to the Lat99 Proceeding

Global Analysis of Neutrino Data

In this talk I review the present status of neutrino masses and mixing and some of their implications for particle physics phenomenology. I first discuss the minimum extension of the Standard Model of particle physics required to accommodate neutrino masses and introduce the new parameters present in the model and in particular the possibility of leptonic mixing. I then describe the phenomenology of neutrino masses and mixing leading to flavour oscillations and present the existing evidence from solar, reactor, atmospheric and long-baseline neutrinos as well as the results from laboratory searches at short distances. I derive the allowed ranges for the mass and mixing parameters when the bulk of data is consistently analyzed in the framework of mixing between the three active neutrinos and obtain as a result the most up-to-date determination of the leptonic mixing matrix. Then I briefly summarize the status of some proposed phenomenological explanations to accommodate the LSND results: the role of sterile neutrinos and the violation of CPT. Finally I comment how within the present experimental precision it is possible to use the observation of oscillation patterns to impose severe constraints on the possible violation of fundamental symmetries in particle physics such as Lorentz invariance or the weak equivalence principle.Comment: Talk given at the Nobel Symposium on Neutrino Physics, Haga Slott, Enkoping, Swede

Anomalous Higgs Couplings

We review the effects of new effective interactions on the Higgs boson phenomenology. New physics in the electroweak bosonic sector is expected to induce additional interactions between the Higgs doublet field and the electroweak gauge bosons leading to anomalous Higgs couplings as well as to anomalous gauge-boson self-interactions. Using a linearly realized $SU(2)_L \times U(1)_Y$ invariant effective Lagrangian to describe the bosonic sector of the Standard Model, we review the effects of the new effective interactions on the Higgs boson production rates and decay modes. We summarize the results from searches for the new Higgs signatures induced by the anomalous interactions in order to constrain the scale of new physics in particular at CERN LEP and Fermilab Te vatron colliders.Comment: 35 pages, latex using epsfig.sty psfig.sty and axodraw.sty, 16 postscript figure

A minor-merger origin for inner disks and rings in early-type galaxies

Nuclear disks and rings are frequent galaxy substructures, for a wide range of morphological types (from S0 to Sc). We have investigated the possible minor-merger origin of inner disks and rings in spiral galaxies through collisionless N-body simulations. The models confirm that minor mergers can drive the formation of thin, kinematically-cold structures in the center of galaxies out of satellite material, without requiring the previous formation of a bar. Satellite core particles tend to be deposited in circular orbits in the central potential, due to the strong circularization experienced by the satellite orbit through dynamical friction. The material of the satellite core reaches the remnant center if satellites are dense or massive, building up a thin inner disk; whereas it is fully disrupted before reaching the center in the case of low-mass satellites, creating an inner ring instead.Comment: 2 pages, 2 figures, Proceedings of the conference "Hunting for the Dark: The Hidden Side of Galaxy Formation", held in Malta, 19-23 Oct. 2009, ed. V. Debattista and C. C. Popescu, AIP Conf. Ser., in pres