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http://hdl.handle.net/10261/49
20140918T20:55:22Z

Condensed matter realization of the axial magnetic effect
http://hdl.handle.net/10261/98797
Title: Condensed matter realization of the axial magnetic effect
Authors: Chernodub, Maxim N.; Cortijo, Alberto; Grushin, Adolfo G.; Landsteiner, Karl; Vozmediano, María A. H.
Abstract: The axial magneticeffect, i.e., the generation of an energy current parallel to an axial magnetic field coupling with opposite signs to left and righthanded fermions, is a nondissipative transport phenomenon intimately related to the gravitational contribution to the axial anomaly. An axial magnetic field emerges naturally in condensed matter in socalled Weyl semimetals. We present a measurable implementation of the axial magnetic effect. We show that the edge states of a Weyl semimetal at finite temperature possess a temperature dependent angular momentum in the direction of the vector potential intrinsic to the system. Such a realization provides a plausible context for the experimental confirmation of the elusive gravitational anomaly. © 2014 American Physical Society.
20140624T07:44:19Z

Consistent highenergy constraints in the anomalous QCD sector
http://hdl.handle.net/10261/96667
Title: Consistent highenergy constraints in the anomalous QCD sector
Authors: Roig, Pablo; Sanz, Juan José
Abstract: The anomalous 〈VVP〉〈VVP〉 Green function and related formfactors (π0→γ⁎γ⁎π0→γ⁎γ⁎ and τ−→X−νττ−→X−ντ vector formfactors, with X−=(KKπ)−X−=(KKπ)−, φ−γφ−γ, (φV)−(φV)−) are analyzed in this letter in the largeNCNC limit. Within the single (vector and pseudoscalar) resonance approximation and the context of Resonance Chiral Theory, we show that all these observables overdetermine in a consistent way a unique set of compatible highenergy constraints for the resonance couplings. This result is in agreement with analogous relations found in the even intrinsicparity sector of QCD like, e.g., View the MathML sourceFV2=3F2. The antisymmetric tensor formalism is considered for the spinone resonance fields. Finally, we have also worked out and provide here the relation between the two bases of odd intrinsicparity Lagrangian operators commonly employed in the literature.
20140514T09:03:08Z

Critical behavior of 3D Z(N)Z(N) lattice gauge theories at zero temperature
http://hdl.handle.net/10261/96611
Title: Critical behavior of 3D Z(N)Z(N) lattice gauge theories at zero temperature
Authors: Borisenko, O.; Chelnokov, V.; Cortese, G.; Gravina, M.; Papa, Anna; Surzhikov, I.
Abstract: Threedimensional Z(N)Z(N) lattice gauge theories at zero temperature are studied for various values of N . Using a modified phenomenological renormalization group, we explore the critical behavior of the generalized Z(N)Z(N) model for N=2,3,4,5,6,8N=2,3,4,5,6,8. Numerical computations are used to simulate vector models for N=2,3,4,5,6,8,13,20N=2,3,4,5,6,8,13,20 for lattices with linear extension up to L=96L=96. We locate the critical points of phase transitions and establish their scaling with N . The values of the critical indices indicate that the models with N>4N>4 belong to the universality class of the threedimensional XY model. However, the exponent α derived from the heat capacity is consistent with the Ising universality class. We discuss a possible resolution of this puzzle.
20140513T11:45:47Z

A geometric Monte Carlo algorithm for the antiferromagnetic Ising model with “topological” term at θ=π
http://hdl.handle.net/10261/96603
Title: A geometric Monte Carlo algorithm for the antiferromagnetic Ising model with “topological” term at θ=π
Authors: Azcoitia, V.; Cortese, G.; Follana, E.; Giordano, Mara
Abstract: In this work we study the two and threedimensional antiferromagnetic Ising model with an imaginary magnetic field iθ at θ=πθ=π. In order to perform numerical simulations of the system we introduce a new geometric algorithm not affected by the sign problem. Our results for the 2D model are in agreement with the analytical solution. We also present new results for the 3D model which are qualitatively in agreement with meanfield predictions.
20140513T11:17:31Z

Antisymmetric tensor Z p gauge symmetries in field theory and string theory
http://hdl.handle.net/10261/96598
Title: Antisymmetric tensor Z p gauge symmetries in field theory and string theory
Authors: BerasaluceGonzález, Mikel; Ramírez, G.; Uranga Urteaga, Ángel M.
Abstract: We consider discrete gauge symmetries in D dimensions arising as remnants of broken continuous gauge symmetries carried by general antisymmetric tensor fields, rather than by standard 1forms. The lagrangian for such a general Z p gauge theory can be described in terms of a rform gauge field made massive by a (r − 1)form, or other dual realizations, that we also discuss. The theory contains charged topological defects of different dimensionalities, generalizing the familiar charged particles and strings in D = 4. We describe realizations in string theory compactifications with torsion cycles, or with background field strength fluxes. We also provide examples of nonabelian discrete groups, for which the group elements are associated with charged objects of different dimensionality.
Description: BerasaluceGonzález, Mikel et al.
20140513T10:58:49Z

Collider signatures of a light NMSSM pseudoscalar in neutralino decays in the light of LHC results
http://hdl.handle.net/10261/96567
Title: Collider signatures of a light NMSSM pseudoscalar in neutralino decays in the light of LHC results
Authors: Cerdeño, David G.; Ghosh, Pradipta; BeomPark, Chan; Peiró, Miguel
Abstract: We investigate signatures induced by a very light pseudoscalar Higgs in neutralino decays in the NexttoMinimal Supersymmetric Standard Model (NMSSM) and determine their observability at the LHC. We concentrate on scenarios which feature two light scalar Higgs bosons (one of them is SMlike with a mass of 125 GeV and a singletlike lighter one) with a very light (singletlike) pseudoscalar Higgs in the mass range 2m τ < ma01 < 2m b . We consider neutralinochargino pair production and the subsequent decay χ˜02,3→ χ˜01a01 , which leads to topologies involving multileptons and missing transverse energy. We determine a set of selection cuts that can effectively isolate the signal from backgrounds of the Standard Model or the Minimal Supersymmetric Standard Model. We also exemplify the procedure with a set of benchmark points, for which we compute the expected number of events and signal strength for LHC with 8 TeV center of mass energy. We show that this signal can already be probed for some points in the NMSSM parameter space.
20140513T09:22:11Z

Holographic superfluids and the Landau criterion
http://hdl.handle.net/10261/96562
Title: Holographic superfluids and the Landau criterion
Authors: Amado, Irene; Areán, Daniel; Jiménez, A.; Landsteiner, Karl; Melgar, Luis; Salazar, I.
Abstract: We revisit the question of stability of holographic superfluids with finite superfluid velocity. Our method is based on applying the Landau criterion to the Quasinormal Mode (QNM) spectrum. In particular we study the QNMs related to the Goldstone modes of spontaneous symmetry breaking with linear and quadratic dispersions. In the linear case we show that the sound velocity becomes negative for large enough superfluid velocity and that the imaginary part of the quasinormal frequency moves to the upper half plane. Since the instability is strongest at finite wavelength, we take this as an indication for the existence of an inhomogeneous or striped condensed phase for large superfluid velocity. In the quadratic case the instability is present for arbitrarily small superfluid velocity.
20140513T09:13:01Z

Sterile neutrinos in leptonic and semileptonic decays
http://hdl.handle.net/10261/96559
Title: Sterile neutrinos in leptonic and semileptonic decays
Authors: Abada, Asmaa; Teixeira, A. M.; Vicente, A.; Weiland, Carlos
Abstract: We address the impact of a modified W ℓν coupling on a wide range of observables, such as τ leptonic and mesonic decays, leptonic decays of pseudoscalar mesons, as well as semileptonic meson decays. In particular, we concentrate on deviations from lepton flavour universality, focusing on the ratios R P = Γ(P → ℓν)/Γ(P → ℓ′ν), with P = K,π,D,D s , R(D) = Γ(B + → Dτ + ν)/Γ(B + → Dℓ + ν), R τ = Γ(τ → μνν)/Γ(τ → eνν), RℓτP = Γ(τ → Pν)/Γ(P → ℓν), and BR(B → τν). We further consider leptonic gauge boson decays, such as W → ℓν and Z → νν. For all the above observables, we provide the corresponding complete analytical expressions, derived for the case of massive neutrinos. Working in the framework of the Standard Model extended by additional sterile fermions, which mix with the active (lefthanded) neutrinos, we numerically study the impact of activesterile mixings on the above mentioned observables.
20140513T09:03:39Z

Disentangling a dynamical Higgs
http://hdl.handle.net/10261/96535
Title: Disentangling a dynamical Higgs
Authors: Brivio, I.; Corbett, T.; Eboli, O. J. P.; Gavela, Mª Belén; GonzalezFraile, J.; GonzálezGarcía, M. C.; Merlo, L.; Rigolin, S.
Abstract: The pattern of deviations from Standard Model predictions and couplings is different for theories of new physics based on a nonlinear realization of the SU(2)L × U(1)Y gauge symmetry breaking and those assuming a linear realization. We clarify this issue in a modelindependent way via its effective Lagrangian formulation in the presence of a light Higgs particle, up to first order in the expansions: dimensionsix operators for the linear expansion and four derivatives for the nonlinear one. Complete sets of gauge and gaugeHiggs operators are considered, implementing the renormalization procedure and deriving the Feynman rules for the nonlinear expansion. We establish the theoretical relation and the differences in physics impact between the two expansions. Promising discriminating signals include the decorrelation in the nonlinear case of signals correlated in the linear one: some pure gauge versus gaugeHiggs couplings and also between couplings with the same number of Higgs legs. Furthermore, anomalous signals expected at first order in the nonlinear realization may appear only at higher orders of the linear one, and vice versa. We analyze in detail the impact of both type of discriminating signals on LHC physics.
20140512T11:37:09Z

Structure formation during an early period of matter domination
http://hdl.handle.net/10261/96497
Title: Structure formation during an early period of matter domination
Authors: Barenboim, Gabriela; Rasero, Javier
Abstract: In this work we show that modifying the thermal history of the Universe by including an early period of matter domination can lead to the formation of astronomical objects. However, the survival of these objects can only be possible if the dominating matter decays to a daughter particle which is not only almost degenerate with the parent particle but also has an open annihilation channel. This requirement translates in an upper bound for the coupling of such a channel and makes the early structure formation viable.
20140512T08:54:21Z