Search

We explore three-Higgs-doublet models that may accommodate scalar Dark Matter where the stability is based on an unbroken U(1)-based symmetry, rather than the familiar ℤ2 symmetry. Our aim is to classify all possible ways of embedding a U(1) symmetry in a three-Higgs-doublet model. The different possibilities are presented and compared. All these models contain mass-degenerate pairs of Dark Matter candidates due to a U(1) symmetry unbroken (conserved) by the vacuum. Most of these models preserve CP. In the CP-conserving case the pairs can be seen as one being even and the other being odd under CP or as having opposite charges under U(1). Not all symmetries presented here were identified before in the literature, which points to the fact that there are still many open questions in three-Higgs-doublet models. We also perform a numerical exploration of the U(1) × U(1)-symmetric 3HDM, this is the most general phase-invariant (real) three-Higgs-doublet model. The model contains a multi-component Dark Matter sector, with two independent mass scales. After imposing relevant experimental constraints we find that there are possible solutions throughout a broad Dark Matter mass range, 45–2000 GeV, the latter being a scan cutoff. [ABSTRACT FROM AUTHOR]

Electrokinetic flows driven by electro-osmotic forces are especially relevant in micro and nano-devices, presenting specific applications in medicine, biochemistry, and miniaturized industrial processes. In this work, we integrate analytical solutions with numerical methodologies to explore the fluid dynamics of viscoelastic electro-osmotic/pressure-driven fluid flows (described by the generalized Phan–Thien–Tanner (gPTT) constitutive equation) in a microchannel under asymmetric zeta potential conditions. The constitutive equation incorporates the Mittag–Leffler function with two parameters (α and β ), which regulate the rate of destruction of junctions in a network model. We analyze the impact of the various model parameters on the velocity profile and observe that our newly proposed model provides a more comprehensive depiction of flow behavior compared to traditional models, rendering it suitable for modeling complex viscoelastic flows. [ABSTRACT FROM AUTHOR]

The annular flow of complex viscoelastic fluids, described by the generalised Phan-Thien–Tanner model, is studied. This model considers the Mittag-Leffler function instead of the usual linear or exponential functions of the trace of the stress tensor, and includes two new parameters that provide additional fitting flexibility. We derive a semi-analytical solution that provides a better understanding of the behaviour of this type of fluid in annular flows and also helps to improve the modelling of complex materials. [ABSTRACT FROM AUTHOR]

CP violation plays a very important role in nature with implications both for Particle Physics and for Cosmology. Accounting for the observed matter-antimatter asymmetry of the Universe requires the existence of new sources of CP violation beyond the Standard Model. In models with an extended scalar sector CP violation can emerge either explicitly, i.e., at the Lagrangian level, or spontaneously. Spontaneous CP violation occurs in the framework of the electroweak symmetry breaking whenever the Lagrangian conserves CP and the vacuum breaks it. This requires that not all vacuum expectation values be real. In the context of multi-Higgs extensions of the Standard Model imposing the existence of a scalar basis where all couplings are real is a sufficient condition for CP to be explicitly conserved. We discuss a three-Higgs-doublet model with an underlying S3 symmetry, allowing in principle for complex couplings. In this framework it is possible to have either spontaneous or explicit CP violation in the scalar sector, depending on the regions of parameter space corresponding to the different possible vacua of the S3 symmetric potential. We list all possible vacuum structures allowing for CP violation in the scalar sector specifying whether it can be explicit or spontaneous. It is by now established that CP is violated in the flavour sector and that the Cabibbo-Kobayashi-Maskawa matrix is complex. In order to understand what are the possible sources of CP violation in the Yukawa sector we analyse the implications of the different available choices of representations for the quarks under the S3 group. This classification is based strictly on the exact S3-symmetric scalar potential with no soft symmetry breaking terms. The scalar sector of one such model was explored numerically. After applying the theoretical and the most important experimental constraints the available parameter space is shown to be able to give rise to light neutral scalars at the O (MeV) scale. [ABSTRACT FROM AUTHOR]

We perform a comprehensive analysis of a version of the 3-Higgs doublet model whose scalar potential is invariant under a global ∆(27) discrete symmetry and where the three scalar doublets are chosen to transform as a triplet under this discrete group. For each of the known tree-level minima we study the mass spectra and use the oblique parameters STU as well as perturbative unitarity to constrain the parameter space of the model. We then discuss phenomenological consequences of some leading order flavour mixing quark Yukawa couplings by considering the flavour violation process b → sγ. We show that perturbative unitarity significantly constrains parameters of the model while, conversely, the beyond the Standard Model contributions to the b → sγ decay are automatically tamed by the symmetry. [ABSTRACT FROM AUTHOR]

We propose a minimal extension of the Standard Model where an up-type vector-like quark, denoted T, is introduced and provides a simple solution to the CKM unitarity problem. We adopt the Botella-Chau parametrization in order to extract the 4 × 3 quark mixing matrix which contains the three angles of the 3 × 3 CKM matrix plus three new angles denoted θ 14 , θ 24 , θ 34 . It is assumed that the mixing of T with standard quarks is dominated by θ 14 . Imposing a recently derived, and much more restrictive, upper-bound on the New Physics contributions to ϵ K , we find, in the limit of exact θ 14 dominance where the other extra angles vanish, that ϵ K NP is too large. However, if one relaxes the exact θ 14 dominance limit, there exists a parameter region, where one may obtain ϵ K NP in agreement with experiment while maintaining the novel pattern of T decays with the heavy quark decaying predominantly to the light quarks d and u. We also find a reduction in the decay rate of K L → π 0 ν ν ¯ . [ABSTRACT FROM AUTHOR]

We point out that hints of deviations from unitarity in the first row of the CKM matrix may be explained by the presence of a single vector-like top. We study how the stringent experimental constraints arising from CP Violation in the kaon sector and from meson mixing such as D 0 ‐ D ¯ 0 , K 0 ‐ K ¯ 0 and B d , s 0 ‐ B ¯ d , s 0 can be satisfied in the proposed framework. In order for the deviations from unitarity to be of the required size while keeping the theory perturbative, the new top quark should have a mass mT ≲ 7 TeV which could be probed in upcoming experiments at the energy frontier. [ABSTRACT FROM AUTHOR]

This work presents new semi-analytical solutions for the combined fully developed electro-osmotic pressure-driven flow in microchannels of viscoelastic fluids, described by the generalised Phan-Thien–Tanner model (gPTT) recently proposed by Ferrás et al. (Journal of Non-Newtonian Fluid Mechanics, 269:88–99, 2019). This generalised version of the PTT model presents a new function for the trace of the stress tensor—the Mittag–Leffler function—where one or two new fitting constants are considered in order to obtain additional fitting flexibility. The semi-analytical solution is obtained under sufficiently weak electric potential that allows the Debye–Hückel approximation for the electrokinetic fields and for thin electric double layers. Based on the solution, the effects of the various relevant dimensionless numbers are assessed and discussed, such as the influence of ε W i 2 , of the parameters α and β of the gPTT model, and also of κ ¯ , the dimensionless Debye–Hückel parameter. We conclude that the new model characteristics enhance the effects of both ε W i 2 and κ ¯ on the velocity distribution across the microchannels. The effects of a high zeta potential and of the finite size of ions are also studied numerically. [ABSTRACT FROM AUTHOR]

We show how a novel fine-tuning problem present in the Standard Model can be solved through the introduction of a $$Z_6$$ flavour symmetry, together with three $$Q = - 1/3$$ quarks, three $$Q = 2/3$$ quarks, as well as a complex singlet scalar. The $$Z_6$$ symmetry is extended to the additional fields and it is an exact symmetry of the Lagrangian, only softly broken in the scalar potential, in order to avoid the domain-wall problem. Specific examples are given and a phenomenological analysis of the main features of the model is presented. It is shown that even for vector-like quarks with masses accessible at the LHC, one can have realistic quark masses and mixing, while respecting the strict constraints on processes arising from flavour changing neutral currents. The vector-like quark decay channels are also described. [ABSTRACT FROM AUTHOR]

F.J.B. research was founded by the Spanish grant PID2019-106448GB-C33 (AEI/FEDER, UE) and by Generalitat Valenciana, under grant PROMETEO 2019-113. G.C.B. and M.N.R. benefited from discussions that were prompted through the HARMONIA project of the National Science Centre, Poland, under contract UMO-2015/18/M/ST2/00518 (2016-2019), which has been extended. J. C (2022) 82:1-16 https://doi.org/10.1140/epjc/s10052-022-10299-9 The Acknowledgements section was missing from this article and should have read: This work was partially supported by Fundação para a Ciência e a Tecnologia (FCT, Portugal) through the projects CFTP-FCT Unit 777 (UIDB/00777/2020 and UIDP/00777/2020), PTDC/FIS-PAR/29436/2017, and CERN/FIS-PAR/0008/2019, which are partially funded through POCTI (FEDER), COMPETE, QREN and EU. [Extracted from the article]

Cadmium bioaccumulation in Nodipecten nodosus reared on a marine farm in a tropical bay was measured in muscle tissue and the digestive glands in animals ranging from 6 to 16 months. No bioaccumulation tendencies regarding Cd concentration were observed in muscle tissue (below 1 μg g), while in the digestive gland concentrations remained below 5 μg g until the organisms reached 10 months, and reached levels above 10 μg g from 12 months onwards (reaching 27 μg g). This is the same bioaccumulation pattern noted in animals transplanted to a different Cd exposure. Allometry and environmental factors cannot explain this sudden increase. [ABSTRACT FROM AUTHOR]

The oxidation of two Fe−Nb alloys containing 15 and 30 wt.% Nb has been studied at 600-800°C under low oxygen pressures, similar to those prevailing in environments of the coal-gasification type. The reaction produced only an internal oxidation of niobium to form two niobium oxides (NbO and NbO) and in some cases a double Fe−Nb oxide. The kinetics of this reaction were very slow at 600°C but rather fast at 700 and 800°C. A peculiar feature of the internal oxidation of these alloys is that the distribution of the internal oxides follows closely that of the Nb-rich phase in the original two-phase alloys. This behavior, as well as the lack of formation of external scales of niobium oxides, is mainly a result of the limited solubility of niobium in iron and of the consequent presence of two metal phases in the alloys. [ABSTRACT FROM AUTHOR]

We consider seesaw type-I models including at least one (mostly-)sterile neutrino with mass at the eV scale. Three distinct situations are found, where the presence of light extra neutrinos is naturally justified by an approximately conserved lepton number symmetry. To analyse these scenarios consistently, it is crucial to employ an exact parametrisation of the full mixing matrix. We provide additional exact results, including generalised versions of the seesaw relation and of the Casas-Ibarra parametrisation, valid for every scale of seesaw. We find that the existence of a light sterile neutrino imposes an upper bound on the lightest neutrino mass. We further assess the impact of light sterile states on short- and long-baseline neutrino oscillation experiments, emphasise future detection prospects, and address CP Violation in this framework via the analysis of CP asymmetries and construction of weak basis invariants. The proposed models can accommodate enough active-sterile mixing to play a role in the explanation of short-baseline anomalies. [ABSTRACT FROM AUTHOR]

We address the question of deviations from 3×3 unitarity of the leptonic mixing matrix showing that, in the framework of type I seesaw mechanism, one may have significant deviations from unitarity that can be detected at the next round of experiments while some of the heavy neutrino masses are sufficiently low to become within experimental reach. For that purpose we introduce a specially useful parametrisation that enables to control all deviations of unitarity through a single 3×3 matrix, which we denote by X and which connects the mixing of the light and heavy neutrinos in the context of type I seesaw. We show that there is no need for the Yukawa couplings to be extremely suppressed. We present specific examples where deviations from 3×3 unitarity are sufficiently small to conform to all the present stringent experimental bounds. [ABSTRACT FROM AUTHOR]