Computing the properties of the bubble wall of a cosmological first order phase transition at electroweak scale is of paramount importance for the correct prediction of the baryon asymmetry of the universe and the spectrum of gravitational waves. By means of the semiclassical formalism we calculate the velocity and thickness of the wall using as theoretical framework the scalar singlet extension of the SM with a parity symmetry and the SM effective field theory supplemented by a dimension six operator. We use these solutions to carefully predict the baryon asymmetry and the gravitational wave signals. The singlet scenario can easily accommodate the observed asymmetry but these solutions do not lead to observable effects at future gravity wave experiments. In contrast the effective field theory fails at explaining the baryon abundance due to the strict constraints from electric dipole moment experiments, however, the strongest solutions we found fall within the sensitivity of the LISA experiment. We provide a simple analytical approximation for the wall velocity which only requires calculation of the strength and temperature of the transition and works reasonably well in all models tested. We find that generically the weak transitions where the fluid approximation can be used to calculate the wall velocity and verify baryogenesis produce signals too weak to be observed in future gravitational wave experiments. Thus, we infer that GW signals produced by simple SM extensions visible in future experiments are likely to only result from strong transitions described by detonations with highly relativistic wall velocities.

We study the possible gravitational wave signal and the viability of baryogenesis arising from the electroweak phase transition in an extension of the Standard Model (SM) by a scalar singlet field without a ℤ2 symmetry. We first analyze the velocity of the expanding true-vacuum bubbles during the phase transition, confirming our previous finding in the unbroken ℤ2 symmetry scenario, where the bubble wall velocity can be computed from first principles only for weak transitions with strength parameters α ≲ 0.05, and the Chapman-Jouguet velocity defines the maximum velocity for which the wall is stopped by the friction from the plasma. We further provide an analytical approximation to the wall velocity in the general scalar singlet scenario without ℤ2 symmetry and test it against the results of a detailed calculation, finding good agreement. We show that in the singlet scenario with a spontaneously broken ℤ2 symmetry, the phase transition is always weak and we see no hope for baryogenesis. In contrast, in the case with explicit ℤ2 breaking there is a region of the parameter space producing a promising baryon yield in the presence of CP violating interactions via an effective operator involving the singlet scalar and the SM top quarks. Yet, we find that this region yields unobservable gravitational waves. Finally, we show that the promising region for baryogenesis in this model may be fully tested by direct searches for singlet-like scalars in di-boson final states at the HL-LHC, combined with present and future measurements of the electron electric dipole moment.

We study a three Higgs doublet model where one doublet is inert and the other two doublets are active. Flavor changing neutral currents are avoided at tree-level by imposing a softly broken Z 2 symmetry and we consider type I and type II Yukawa structures. The lightest inert scalar is a viable Dark Matter (DM) candidate. A numerical scan of the free parameters is performed taking into account theoretical constraints such as positivity of the scalar potential and unitarity of 2 → 2 scattering amplitudes. The model is further constrained by experimental results such as B physics lower limits on charged Higgs masses, Electroweak Precision Observables, LEP II, LHC Higgs measurements, Planck measurement of the DM relic abundance and WIMP direct searches by the LUX and XENON1T experiments. The model predictions for mono-jet, mono Z and mono Higgs final states are studied and tested against current LHC data and we find the model to be allowed. Projected sensitivities of direct detection experiments will leave only a tiny window in the DM mass versus coupling plane that is compliant with relic density bounds.

We extend the work of Carone, Chaurasia and Vasquez on non-supersymmetric models of flavor based on the double tetrahedral group. Three issues are addressed: (1) the sector of flavorsymmetry-breaking fields is simplified and their potential studied explicitly, (2) a flavorful axion is introduced to solve the strong CP problem and (3) the model is extended to include the neutrino sector. We show how the model can accommodate the strong hierarchies manifest in the charged fermion Yukawa matrices, while predicting a qualitatively different form for the light neutrino mass matrix that is consistent with observed neutrino mass squared differences and mixing angles.The structure of the fermion Yukawa couplings in the standard model may result from the sequential breaking of a horizontal discrete family symmetry. Long ago, Aranda, Carone and Lebed [1, 2] showed how the double tetrahedral group T ′ could be used to construct successful supersymmetric flavor models that are similar to those based on U(2) symmetry [3,4], with or without the assumption of conventional supersymmetric grand unification. For other early work on T ′ as a flavor symmetry, see Ref. [5]. Many other authors have since explored the use of T ′ symmetry in models that aim to address the flavor structure of the standard model [6].Much of the work on T ′ flavor models has assumed weak-scale supersymmetry, to stabilize the hierarchy between the weak scale and the grand unified or Planck scale. Over the past decade, however, there has been no direct evidence for superpartners at the LHC, nor indirect evidence in the form of a convincing pattern of deviations from the predictions of the standard model for some subset of its observables. While one cannot exclude the possibility that supersymmetry is present and just beyond the reach of current experiments (a statement that applies to any new physics that has a decoupling limit), the current state of affairs has motivated a greater open-mindedness towards consideration of non-supersymmetric extensions of the standard model. For example, the possibility that the standard model could arise consistently from a string theory without supersymmetry has been discussed in Ref. [7].The hierarchies between mass scales might result from dynamical mechanisms (for example, cosmic relaxation [8] or Nnaturalness [9]), or anthropic selection [10]. On the other hand, the fundamental mass scales found in nature may simply be random and fine tuned, for reasons that are obscure to us at present. In this work, we assume the absence of supersymmetry and focus on phenomenological issues, while remaining agnostic on the question of naturalness.The purpose of the present work is to further explore the possibility of nonsupersymmetric models of flavor based on T ′ symmetry, following a study by Carone, Chaurasia and Vasquez [11]. In Ref. [11], a nonsupersymmetric T ′ model was presented in which the flavor scale M F was treated as a free parameter. (There is less motivation to link the flavor scale to a grand unified scale in a frame...