Flavor Physics in the Randall-Sundrum Model: I. Theoretical Setup and Electroweak Precision Tests

A complete discussion of tree-level flavor-changing effects in the Randall-Sundrum (RS) model with brane-localized Higgs sector and bulk gauge and matter fields is presented. The bulk equations of motion for the gauge and fermion fields, supplemented by boundary conditions taking into account the couplings to the Higgs sector, are solved exactly. For gauge fields the Kaluza-Klein (KK) decomposition is performed in a covariant R_xi gauge. For fermions the mixing between different generations is included in a completely general way. The hierarchies observed in the fermion spectrum and the quark mixing matrix are explained naturally in terms of anarchic five-dimensional Yukawa matrices and wave-function overlap integrals. Detailed studies of the flavor-changing couplings of the Higgs boson and of gauge bosons and their KK excitations are performed, including in particular the couplings of the standard W and Z bosons. A careful analysis of electroweak precision observables including the S and T parameters and the Zbb couplings shows that the simplest RS model containing only Standard Model particles and their KK excitations is consistent with all experimental bounds for a KK scale as low as a few TeV, if one allows for a heavy Higgs boson and/or for an ultra-violet cutoff below the Planck scale. The study of flavor-changing effects includes analyses of the non-unitarity of the quark mixing matrix, anomalous right-handed couplings of the W bosons, tree-level flavor-changing neutral current couplings of the Z and Higgs bosons, the rare decays t-->c(u)+Z and t-->c(u)+h, and the flavor mixing among KK fermions. The results obtained in this work form the basis for general calculations of flavor-changing processes in the RS model and its extensions.Comment: 70 pages, 12 figures. v2: Incorrect treatment of phases in zero-mode approximation corrected, and discussion of electroweak precision tests modified. v3: Additional minor modifications and typos corrected; version published in JHE

Nonstandard electroconvection in a bent-core oxadiazole material

Electroconvection (EC) phenomena have been investigated in the nematic phase of a bent-core oxadiazole material with negative dielectric anisotropy and a frequency dependent conductivity anisotropy. The formation of longitudinal roll (LR) patterns is one of the predominant features observed in the complete frequency and voltage range studied. At voltages much above the LR threshold, various complex patterns such as the "crisscrossed" pattern, bimodal varicose, and turbulence are observed. Unusually, the nonstandard EC (ns-EC) instability in this material, is observed in a regime in which we measure the dielectric and conductivity anisotropies to be negative and positive respectively. A further significant observation is that the EC displays distinct features in the high and low temperature regimes of the nematic phase, supporting an earlier report that EC patterns could distinguish between regions that have been reported as uniaxial and biaxial nematic phases

Dark matter and nature of electroweak phase transition with an inert doublet

We provide a comprehensive and up-to-date analysis of the prospects to realize Dark Matter (DM) in the Inert Doublet Model, while simultaneously enhancing the Electroweak Phase Transition (EWPhT) such as to allow for electroweak baryogenesis. Instead of focusing on certain aspects or mass hierarchies, we perform extensive, yet fine-grained, parameter space scans, where we analyze the nature of the EWPhT in both the light and the heavy DM regions, confronting it with the amount of DM potentially residing in the lightest inert-doublet state. Thereby, we point out a viable region where a non-trivial two-step EWPhT can appear, without being in conflict with direct-detection bounds, which could leave interesting imprints in gravitational wave signatures. We propose new benchmarks with this feature as well as update benchmarks with a strong first-order transition in the light of new XENON1T limits. Moreover, taking into account these latest bounds as well as relevant collider constraints, we envisage a new region for light DM with a small mass splitting, lifting the usual assumption of exact degeneracy of the new non-DM scalars, such as to avoid collider bounds while providing a fair DM abundance over a rather large DM mass range. This follows from a detailed survey of the impact of co-annihilations on the abundance, dissecting the various channels

ENERGY BASED SEISMIC DESIGN OF A TIMBER CORE-WALL MULTI-STOREY HYBRID BUILDING

Current earthquake design philosophy in North America recommends an equivalent static force procedure (ESFP). Much research lately has been in new performance based methodologies including direct displacement based design (DDBD) and energy-based design (EBD). Research in energy-based design has not had the attention of DDBD yet now is gaining in popularity because of the methods reliance on the velocity spectrum and duration of earthquake hazard. This paper discusses an energy based methodology in designing a novel multi-storey hybrid building consisting of a timber-steel core wall system. This hybrid system combines Cross Laminated Timber (CLT) panels with steel plates and connections to provide the required strength and ductility to core walled buildings. To improve the applicability of the hybrid system an EBD methodology is proposed to design the core-walled building. The methodology is proposed as it does not rely on empirical formulas and force modification factors to determine the final design of the structure. In order to assess the feasibility of the EBD method, it is implemented in the design of a 7-storey building based off an already built concrete benchmark building. The design is first carried out following the ESFP outlined by the National Building Code of Canada for Vancouver, BC. Nonlinear time history analysis is carried out on the ESFP design and the proposed EBD methodology using 10 ground motions selected at 2% in 50 years return period, to evaluate the suitability of the method and the results of the ESFP and EBD methodologies are discussed and compared

Z₂ Non-Restoration and Composite Higgs: Singlet-Assisted Baryogenesis w/o Topological Defects

Simple scalar-singlet extensions of the Standard Model with a (spontaneouslybroken) $Z_2$ symmetry allow for a strong first order electroweak phasetransition, as sought in order to realize electroweak baryogenesis. Howeverthey generically also lead to the emergence of phenomenologically problematicdomain walls. Here we present a framework with a real scalar singlet thatfeatures a different thermal history that avoids this problem by neverrestoring the $Z_2$ symmetry in the early universe. This is accomplished byconsidering $D>4$ operators that emerge on general grounds, understanding themodel as the low energy tail of a more complete theory, like for example incomposite Higgs scenarios. Sticking to the latter framework, we present aconcrete $SO(6)/SO(5)$ composite realization of the idea. To this end, weadditionally provide a complete classification of the structure of the Higgspotential (and the Yukawa couplings) in $SO(6)/SO(5)$ models with fermions inthe ${\bf 1, 6, 15}$ or ${\bf 20^\prime}$ of $SO(6)$.<br

The Hierarchy Problem and the Top Yukawa: An Alternative to Top Partner Solutions

We discuss the role of the top-quark Yukawa coupling $y_t$ concerning thehierarchy problem and construct an alternative scheme to the conventionalsolutions with top partners. In traditional models, like SUSY or compositeHiggs, top partners cancel the top loop contribution to the Higgs quadraticterm. The lack of evidence for such colored partners however drives thesemodels into more and more fine-tuned regions. Here, an alternative means tomitigate the top loop, allowing for natural electroweak symmetry breaking, ispresented. Emphasizing that we have not measured the top-Higgs interactions athigh scales yet, we envisage scenarios where this interaction is onlyapproaching its sizable strength in the infra-red, but gets strongly suppressedat high scales. We first discuss possible effects via a modification of therunning of the top Yukawa coupling. Then, we turn to models where the topYukawa is generated at one-loop level. Originated from a dimension-sixoperator, it drops when crossing the mass threshold of new degrees of freedom.In either case, the top partners are replaced by some new top-philic particleswith strong interaction. Thus, a very different phenomenology, such as largetop mass running and signals in four top final states, is introduced, whichwill be discussed in detail. With the assistance of this mechanism, thesolution to the hierarchy problem can be pushed to a (well-defined) higherscale, and a final test of naturalness might be deferred to a 100 TeV Collider,like the FCC.<br

The Hierarchy Problem and the Top Yukawa: An Alternative to Top Partner Solutions

We discuss the role of the top-quark Yukawa coupling $y_t$ concerning thehierarchy problem and construct an alternative scheme to the conventionalsolutions with top partners. In traditional models, like SUSY or compositeHiggs, top partners cancel the top loop contribution to the Higgs quadraticterm. The lack of evidence for such colored partners however drives thesemodels into more and more fine-tuned regions. Here, an alternative means tomitigate the top loop, allowing for natural electroweak symmetry breaking, ispresented. Emphasizing that we have not measured the top-Higgs interactions athigh scales yet, we envisage scenarios where this interaction is onlyapproaching its sizable strength in the infra-red, but gets strongly suppressedat high scales. We first discuss possible effects via a modification of therunning of the top Yukawa coupling. Then, we turn to models where the topYukawa is generated at one-loop level. Originated from a dimension-sixoperator, it drops when crossing the mass threshold of new degrees of freedom.In either case, the top partners are replaced by some new top-philic particleswith strong interaction. Thus, a very different phenomenology, such as largetop mass running and signals in four top final states, is introduced, whichwill be discussed in detail. With the assistance of this mechanism, thesolution to the hierarchy problem can be pushed to a (well-defined) higherscale, and a final test of naturalness might be deferred to a 100 TeV Collider,like the FCC.<br

Holographic Composite Higgs Model Building: Soft Breaking, Maximal Symmetry, and the Higgs Mass

We study the emergence and phenomenological consequences of recently proposednew structures, namely soft breaking of the Higgs shift symmetry and `maximalsymmetry' of the composite sector, in holographic realizations of compositeHiggs models. For the former, we show that soft breaking can also successfullybe implemented in a full 5D warped model, where symmetry-restoring universalboundary conditions for the fermion fields allow to break the problematicconnection between a realistically light Higgs and anomalously light toppartners. For the latter, we demonstrate that the minimal incarnation ofmaximal symmetry in the holographic dual leads to a sharp prediction of$m_h\approx 197$ GeV for $f=800$ GeV. We find that a viable implementation ispossible with sizable negative gauge brane kinetic terms, allowing for$m_h=125$ GeV. Overall, both approaches offer promising directions to improvethe naturalness also of holographic realizations of composite Higgs models.<br

Comment on "PIC simulations of circularly polarised Alfv\'en wave phase mixing: A new mechanism for electron acceleration in collisionless plasmas" by Tsiklauri et al

Tsiklauri et al. recently published a theoretical model of electron acceleration by Alfv\'en waves in a nonuniform collisionless plasmas. We compare their work with a series of results published earlier by an another team, of which Tsiklauri et al. were probably unaware. We show that these two series of works, apparently conducted independently, lead to the same conclusions. This reinforces the theoretical consistency of the model.Comment: 2 pages. Accepted at "Astronomy and Astrophysics

Axiflavon-Higgs Unification

In this talk, a unified model of scalar particles that addresses the flavour hierarchies, solves the strong CP problem, delivers a dark matter candidate, and radiatively triggers electroweak symmetry breaking is discussed. The recently proposed axiflavon is embedded together with an (elementary) Goldstone Higgs-sector in a single multiplet (and thereby also a model of flavour and strong CP conservation for the latter is provided). Bounds on the axion decay constant follow from requiring a SM-like Higgs potential at low energies and are confronted with constraints from flavour physics and astrophysics. In the minimal implementation, the axion decay constant is restricted to $f_a \approx (10^{11}-10^{12})$ GeV, while adding right-handed neutrinos allows for a heavy-axion model at lower energies, down to $f_a \sim 10$ TeV