Supersymmetry breaking with quasi-localized fields in orbifold field theories

We study the Scherk-Schwarz supersymmetry breaking in five-dimensional orbifold theories with five-dimensional fields which are not strictly localized on the boundaries (quasi-localized fields). We show that the Scherk-Schwarz (SS) mechanism, besides the SS parameter \omega, depends upon new parameters, e.g. supersymmetric five-dimensional odd mass terms, governing the level of localization on the boundaries of the five-dimensional fields and study in detail such a dependence. Taking into account radiative corrections, the value of \omega is dynamically allowed to acquire any value in the range 0< \omega < 1/2.Comment: 13 pages, 3 figure

Radius Stabilization by Two-Loop Casimir Energy

It is well known that the Casimir energy of bulk fields induces a non-trivial potential for the compactification radius of higher-dimensional field theories. On dimensional grounds, the 1-loop potential is ~ 1/R^4. Since the 5d gauge coupling constant g^2 has the dimension of length, the two-loop correction is ~ g^2/R^5. The interplay of these two terms leads, under very general circumstances (including other interacting theories and more compact dimensions), to a stabilization at finite radius. Perturbative control or, equivalently, a parametrically large compact radius is ensured if the 1-loop coefficient is small because of an approximate fermion-boson cancellation. This is similar to the perturbativity argument underlying the Banks-Zaks fixed point proposal. Our analysis includes a scalar toy model, 5d Yang-Mills theory with charged matter, the examination of S^1 and S^1/Z_2 geometries, as well as a brief discussion of the supersymmetric case with Scherk-Schwarz SUSY breaking. 2-Loop calculability in the S^1/Z_2 case relies on the log-enhancement of boundary kinetic terms at the 1-loop level.Comment: 18 pages, 2 figures, uses axodraw, references adde

Kaehler Corrections for the Volume Modulus of Flux Compactifications

No-scale models arise in many compactifications of string theory and supergravity, the most prominent recent example being type IIB flux compactifications. Focussing on the case where the no-scale field is a single unstabilized volume modulus (radion), we analyse the general form of supergravity loop corrections that affect the no-scale structure of the Kaehler potential. These corrections contribute to the 4d scalar potential of the radion in a way that is similar to the Casimir effect. We discuss the interplay of this loop effect with string-theoretic alpha' corrections and its possible role in the stabilization of the radion.Comment: 8 pages, references adde

Probing new physics in diphoton production with proton tagging at the Large Hadron Collider

The sensitivities to anomalous quartic photon couplings at the Large Hadron Collider are estimated using diphoton production via photon fusion. The tagging of the protons proves to be a very powerful tool to suppress the background and unprecedented sensitivities down to $6 \cdot 10^{-15}$\gev$^{-4}$ are obtained, providing a new window on extra dimensions and strongly-interacting composite states in the multi-TeV range. Generic contributions to quartic photon couplings from charged and neutral particles with arbitrary spin are also presented.Comment: 4 pages, 3 figure

Radiative brane-mass terms in D>5 orbifold gauge theories

A gauge theory with gauge group G defined in D>4 space-time dimensions can be broken to a subgroup H on four dimensional fixed point branes, when compactified on an orbifold. Mass terms for extra dimensional components of gauge fields A_i (brane scalars) might acquire (when allowed by the brane symmetries) quadratically divergent radiative masses and thus jeopardize the stability of the four-dimensional theory. We have analyzed Z_2 compactifications and identified the brane symmetries remnants of the higher dimensional gauge invariance. No mass term is allowed for D=5 while for D>5 a tadpole \epsilon^{ij}F_{ij}^\alpha can appear when there are U_\alpha(1) factors in H. A detailed calculation is done for the D=6 case and it is established that the tadpole is related, although does not coincide, with the U_\alpha(1) anomaly induced on the brane by the bulk fermions. In particular, no tadpole is generated from gauge bosons or fermions in real representationsComment: 12 pages, 2 figures, axodraw.sty. v2: important typoes corrected and reference added. v3: logarithmic corrections to tadpole include

First steps towards smart drying of beef slices seasoned with different pre-treatments

In this study, beef slices seasoned with salt (S) and salt and vinegar (S+V) were dried at 60 °C in a convective drier and the development of moisture ratio (MR) and colour change (ΔE) was compared to blind samples (B). Hyperspectral imaging (HSI) was applied to create prediction models for moisture content and L, a* and b* values. Regression coefficients of >0.9 could be achieved related to each pre-treatment, but also for combined data of all the pre-treatments

Allosteric modulation of retinal GABA receptors by ascorbic acid

Ionotropic GABA receptors (GABAA and GABAC) belong to the Cys-loop receptor family of ligand-gated ion channels. GABAC receptors are highly expressed in the retina, mainly localized at the axon terminals of bipolar cells. Ascorbic acid, an endogenous redox agent, modulates the function of diverse proteins, and basal levels of ascorbic acid in the retina are very high. However, the effect of ascorbic acid on retinal GABA receptors has not been studied. Here we show that the function of GABAC and GABAA receptors is regulated by ascorbic acid. Patch-clamp recordings from bipolar cell terminals in goldfish retinal slices revealed that GABAC receptor-mediated currents activated by tonic background levels of extracellular GABA, and GABAC currents elicited by local GABA puffs, are both significantly enhanced by ascorbic acid. In addition, a significant rundown of GABA puff-evoked currents was observed in the absence of ascorbic acid. GABA-evoked Cl- currents mediated by homomeric ρ1 GABAC receptors expressed in Xenopus laevis oocytes were also potentiated by ascorbic acid in a concentration-dependent, stereo-specific, reversible, and voltage-independent manner. Studies involving the chemical modification of sulfhydryl groups showed that the two Cys-loop cysteines and histidine 141, all located in the ρ1 subunit extracellular domain, each play a key role in the modulation of GABAC receptors by ascorbic acid. Additionally, we show that retinal GABAA IPSCs and heterologously expressed GABAA receptor currents are similarly augmented by ascorbic acid. Our results suggest that ascorbic acid may act as an endogenous agent capable of potentiating GABAergic neurotransmission in the CNS.Fil: Calero, Cecilia Ines. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones en Ingeniería Genética y Biología Molecular "Dr. Héctor N. Torres"; ArgentinaFil: Vickers, Evan. Oregon Health and Science University; Estados UnidosFil: Cid, Gustavo Moraga. Universidad de Concepción; ChileFil: Aguayo, Luis G.. Universidad de Concepción; ChileFil: von Gersdorff, Henrique. Oregon Health and Science University; Estados UnidosFil: Calvo, Daniel Juan. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones en Ingeniería Genética y Biología Molecular "Dr. Héctor N. Torres"; Argentin

Fermions and Supersymmetry Breaking in the Interval

We study fermions, such as gravitinos and gauginos in supersymmetric theories, propagating in a five-dimensional bulk where the fifth dimensional component is assumed to be an interval. We show that the most general boundary condition at each endpoint of the interval is encoded in a single complex parameter representing a point in the Riemann sphere. Upon introducing a boundary mass term, the variational principle uniquely determines the boundary conditions and the bulk equations of motion. We show the mass spectrum becomes independent from the Scherk-Schwarz parameter for a suitable choice of one of the two boundary conditions. Furthermore, for any value of the Scherk-Schwarz parameter, a zero-mode is present in the mass spectrum and supersymmetry is recovered if the two complex parameters are tuned.Comment: 10 pages. v2: Paragraph on off-shell globally supersymmetric Lagrangian added. Version published in PL

Scherk-Schwarz Supersymmetry Breaking with Radion Stabilization

We study the issue of radion stabilization within five-dimensional supersymmetric theories compactified on the orbifold S^1/Z_2. We break supersymmetry by the Scherk-Schwarz mechanism and explain its implementation in the off-shell formulation of five dimensional supergravity in terms of the tensor and linear compensator multiplets. We show that radion stabilization may be achieved by radiative corrections in the presence of five-dimensional fields which are quasi-localized on the boundaries through the presence of Z_2 odd mass terms. For the mechanism to work the number of quasi-localized fields should be greater than 2+N_V-N_h where N_V and N_h are the number of massless gauge- and hypermultiplets in the bulk. The radion is stabilized in a metastable Minkowski vacuum with a lifetime much larger than cosmological time-scales. The radion mass is in the meV range making it interesting for present and future measurements of deviations from the gravitational inverse-square law in the submillimeter range.Comment: 16 pages, 4 figure