We show that supersymmetric “new physics” beyond the minimal supersymmetric standard model can naturally accommodate a Higgs mass near 126 GeV and enhance the signal rate in the $h\to \gamma \gamma$ channel, while the signal rates in all the other Higgs decay channels coincide with Standard Model expectations, except possibly the $h\to Z\gamma$ channel. The new physics that corrects the relevant Higgs couplings can be captured by two supersymmetric effective operators. We provide a simple example of an underlying model in which these operators are simultaneously generated. The scale of new physics that generates these operators can be around 5 TeV or larger, and outside the reach of the LHC.

We study two-color QCD in a constant external magnetic background at finite temperature using the Polyakov-loop extended two-flavor two-color Nambu-Jona-Lasinio model. At $T=0$, the chiral condensate is calculated and it is found to increase as a function of the magnetic field $B$. In the chiral limit the deconfinement transition lies below the chiral transition for nonzero magnetic fields $B$. At the physical point, the two transitions seem to coincide for field strengths up to $|qB|\approx 5M_{\pi }^2$, where $M_{\pi }=140\mathrm{MeV}$, whereafter they split, and the deconfinement transition takes place first. The splitting between the two increases as a function of $B$ in both the chiral limit and at the physical point. At the physical point, the transition temperature decreases slightly for magnetic fields up to $|qB|\approx 3M_{\pi }^2$, whereafter it increases monotonically. In the chiral limit, this behavior is less pronounced. This change of slope is absent in the Nambu-Jona-Lasinio model where $T_c$ increases for all values of $|qB|$. In the range from zero magnetic field and $|qB|=20M_{\pi }^2$, the transition temperature for the chiral transition increases by approximately 35 MeV, while the transition temperature for deconfinement is essentially constant.

We describe the application of the continuous wavelet transform to calculation of the Green functions in quantum field theory: scalar ${\varphi }^4$ theory, quantum electrodynamics, and quantum chromodynamics. The method of continuous wavelet transform in quantum field theory, presented by Altaisky [Phys. Rev. D 81, 125003 (2010)] for the scalar ${\varphi }^4$ theory, consists in substitution of the local fields $\varphi (x)$ by those dependent on both the position $x$ and the resolution $a$. The substitution of the action $S[\varphi (x)]$ by the action $S[{\varphi }_a(x)]$ makes the local theory into a nonlocal one and implies the causality conditions related to the scale $a$, the region causality [J. D. Christensen and L. Crane, J. Math. Phys. (N.Y.) 46, 122502 (2005)]. These conditions make the Green functions $G(x_1,a_1,\dots ,x_n,a_n)=⟨{\varphi }_{a_1}(x_1)\dots {\varphi }_{a_n}(x_n)⟩$ finite for any given set of regions by means of an effective cutoff scale $A=\min (a_1,\dots ,a_n)$.

Teleparallel theories of gravity have a long history. They include a special case referred to as the teleparallel equivalent of general relativity (TEGR, also known as ${\mathrm{GR}}_{\parallel }$). Recently this theory has been generalized to $f(T)$ gravity. Tight constraints from observations suggest that $f(T)$ gravity is not as robust as initially hoped. This might hint at hitherto undiscovered problems at the theoretical level. In this work, we point out that a generic $f(T)$ theory can be expected to have certain problems including superluminal propagating modes, the presence of which can be revealed by using the characteristic equations that govern the dynamics in $f(T)$ gravity and/or the Hamiltonian structure of the theory via Dirac constraint analysis. We use several examples from simpler gauge field theories to explain how such superluminal modes could arise. We also point out problems with the Cauchy development of a constant time hypersurface in Friedmann-Lemaître-Roberson-Walker (FLRW) spacetime in $f(T)$ gravity. The time evolution from a FLRW (and as a special case, Minkowski spacetime) initial condition is not unique.

A candidate parametrization is introduced, in an effective field theory framework, for the quantum information transfer from a black hole that is necessary to restore unitarity. This in particular allows for description of the effects of this information transfer in the black hole atmosphere, for example seen by infalling observers. In the presence of such information transfer, it is shown that infalling observers need not experience untoward violence. Moreover, the presence of general moderate-frequency couplings to field modes with high angular momenta offers a mechanism to enhance information transfer rates, commensurate with the increased energy flux, when a string is introduced to “mine” a black hole. Generic such models for nonviolent information transfer predict extra energy flux from a black hole, beyond that of Hawking.

We study the linearization of a class of thick $K$-branes, namely, four-dimensional domain walls generated by a scalar field with particular nonstandard kinetic terms. The master equations for linear perturbations are derived from the point of view of both dynamical equations and quadratic action. The spectra of the canonical normal modes are studied using supersymmetric quantum mechanics. Our results indicate that the scalar perturbation is nonlocalizable in general. Conditions for stable $K$-branes are also found.

Massive bosonic fields of arbitrary spin are predicted by general extensions of the standard model. It has been recently shown that there exists a family of bimetric theories of gravity—including massive gravity—which are free of Boulware-Deser ghosts at the nonlinear level. This opens up the possibility to describe consistently the dynamics of massive spin-2 particles in a gravitational field. Within this context, we develop the study of massive spin-2 fluctuations—including massive gravitons—around Schwarzschild and slowly rotating Kerr black holes. Our work has two important outcomes. First, we show that the Schwarzschild geometry is linearly unstable for small tensor masses, against a spherically symmetric mode. Second, we provide solid evidence that the Kerr geometry is also generically unstable, both against the spherical mode and against long-lived superradiant modes. In the absence of nonlinear effects, the observation of spinning black holes bounds the graviton mass $\mu$ to be $\mu \lesssim 5\times {10}^{-23}\mathrm{eV}$.

Neutron stars are extremely relativistic objects which abound in our universe and yet are poorly understood, due to the high uncertainty on how matter behaves in the extreme conditions which prevail in the stellar core. It has recently been pointed out that the moment of inertia $I$, the Love number $\lambda$, and the spin-induced quadrupole moment $Q$ of an isolated neutron star, are related through functions which are practically independent of the equation of state. These surprising universal $I-\lambda -Q$ relations pave the way for a better understanding of neutron stars, most notably via gravitational-wave emission. Gravitational-wave observations will probe highly dynamical binaries and it is important to understand whether the universality of the $I-\lambda -Q$ relations survives strong-field and finite-size effects. We apply a post-Newtonian-affine approach to model tidal deformations in compact binaries and show that the $I-\lambda$ relation depends on the inspiral frequency, but is insensitive to the equation of state. We provide a fit for the universal relation, which is valid up to a gravitational wave frequency of $\sim 900\mathrm{Hz}$ and accurate to within a few percent. Our results strengthen the universality of $I-\lambda -Q$ relations, and are relevant for gravitational-wave observations with advanced ground-based interferometers. We also discuss the possibility of using the Love-compactness relation to measure the neutron-star radius with an uncertainty $\lesssim 10\%$ from gravitational-wave observations.

We propose a new reconstruction method for scalar-tensor gravity based on the use of conformal transformations. The new method allows the derivation of a set of interesting exact cosmological solutions in Brans-Dicke gravity as well as other extensions of general relativity.

In this work I discuss the dynamical and thermodynamical equivalence between a general $k$-essence scalar field cosmology and an arbitrary cosmological model with a decaying vacuum, thus generalizing the approach proposed by Maia and Lima [Phys. Rev. D 65, 083513 (2002)]. The formalism obtained is quite general and holds for any noncanonical scalar field model. As a special case I derive a Dirac-Born-Infeld model with an exponential potential and constant speed of sound, and show that it is equivalent to a cosmological model with decay law $\Lambda (H)=3\beta H^2$.

By using the Gauss-Bonnet formula, the integral of the Gaussian curvature over a 2-surface enclosed by a curve in the asymptotically flat region of a static spacetime was found to be a measure of a gravitational analogue of the Aharonov-Bohm effect by Ford and Vilenkin in the linearized regime. Employing the $1+3$ formulation of spacetime decomposition, we study the same effect in the context of the full Einstein field equations for stationary spacetimes. Applying our approach to static tubelike and cylindrical distributions of dust, not only do we recover their result but we also obtain an extra term which is interpreted to be representing the classical version of the Colella-Overhauser-Werner effect (the Colella-Overhauser-Werner experiment).

We present the most general (six-helicity) angular analysis of $B_s^0\to V_1(\to P_1{P}_1^{\prime })V_2(\to P_2{P}_2^{\prime })$ ($V_i$ is a vector meson, and $P_i$, $P_i^{\prime }$ are pseudoscalars). We focus on final states accessible to both $B_s^0$ and ${\overline{B}}_s^0$-these are mainly $\overline{b}\to \overline{s}$ penguin decays. We also derive the most general decay amplitude, and discuss the differences between it and that used by LHCb in its analysis of $B_s^0\to \varphi \varphi$. In the standard model, all $CP$ violation is predicted to be small, so that the simple measurement of a sizeable $CP$-violating observable indicates the presence of new physics. A full fit to the data is not necessary. By determining which of the $CP$-violating observables are nonzero, one can learn about the structure of the underlying new physics. Finally, we apply the angular analysis to $B_s^0\to K^{*0}{\overline{K}}^{*0}$, and show that there are numerous $CP$-violating observables that remain in the untagged data sample.

Among the class of models with small mixing angles between sterile and active neutrinos, we place constraints on the effective muon-to-sterile neutrino magnetic and electric dipole transition moments from the combined MiniBooNE results for the sterile neutrino mass range of $10\mathrm{MeV}<m_s<500\mathrm{MeV}$. Our results are valid for models with $CP$-violating interactions and for Dirac and Majorana sterile neutrinos. In addition, we show that such dipole electromagnetic interactions cannot be the main source of the anomalous events in the MiniBooNE experiment because they fail to reproduce the anomalous event distribution as a function of polar angle. However, good agreement with the anomalous event distribution in reconstructed energy can be achieved for some values of magnetic and electric moments.

We study neutrino masses and mixing in the context of flavor models with $A_4$ symmetry, three scalar doublets in the triplet representation, and three lepton families. We show that there is no representation assignment that yields a dimension-5 mass operator consistent with experiment. We then consider a type-I seesaw with three heavy right-handed neutrinos, explaining in detail why it fails, and allowing us to show that agreement with the present neutrino oscillation data can be recovered with the inclusion of dimension-3 heavy neutrino mass terms that break softly the $A_4$ symmetry.

We consider a supersymmetric model motivated by a $SO(10)$ grand unified theory: the gauge sector near the supersymmetry scale consists of $SU(3{)}_c\times SU(2{)}_L\times U(1{)}_R\times U(1{)}_{B-L}$. We embed this model in minimal gauge mediation and incorporate neutrino data via an inverse seesaw mechanism. Also in this restricted model, the additional $D$ terms can raise the light Higgs mass in a sizable way. Therefore, it is much easier to obtain $m_h\simeq 125\mathrm{GeV}$ without the need to push the supersymmetry spectrum to extremely large values as it happens in models with minimal supersymmetric standard model particle content only. We show that this model predicts a diphoton rate of the Higgs equal to or smaller than the standard model expectation. We discuss briefly the collider phenomenology with a particular focus on the next to lightest supersymmetric particle in which this model offers the sneutrino as an additional possiblity. Moreover, we point out that, also in this model variant, supersymmetry can be discovered in $Z^{\prime }$ decays even in scenarios in which the strongly interacting particles are too heavy to be produced at a sizable rate at the LHC with 14 TeV. In addition, we show that lepton flavor violating observables constrain the size of the neutrino Yukawa couplings for which, in particular, muon decays and $\mu -e$ conversion in heavy atoms are of particular importance. Once these constraints are fulfilled, the rates for $\tau$ decays are predicted to be below the reach of near-future experiments.

The recently observed boson at 125 GeV could be a light composite scalar from near-conformal technicolor dynamics: a technicolor Higgs. If this is the case, the unitarization of longitudinal weak boson scattering amplitudes, which is due to exchanges of the Higgs and spin-one vector technimesons, is expected to occur in a strong regime, with saturation of the unitarity bounds. This implies that $pp\to VVjj$ processes, where $V$ is either a $W$ or a $Z$ boson, are enhanced, relative to the standard model. We show that this allows probing near-conformal technicolor for couplings and masses of the spin-one resonances which are not directly accessible for direct Drell-Yan production.

If the Higgs-like particle at 125 GeV is the Standard Model (SM) Higgs boson, then SM4, the simplest four generation (4G) extension of the SM, is inconsistent with the most recent LHC data. However, 4G variations (BSM4) are possible if the new particle is not the SM Higgs boson and/or if other new quanta modify its production and decay rates. Since LHC searches have pushed 4G quarks to high mass and strong coupling where perturbation theory eventually fails, we examine the leading nondecoupling electroweak (EW) corrections at two loop order to estimate the domain of validity for perturbation theory. We find that the two loop hypercharge correction, which has not been included in previous EW fits of 4G models, makes the largest quark sector contribution to the rho parameter, much larger even than the nominally leading one loop term. Because it is large and negative, it has a big effect on the EW fits. It does not invalidate perturbation theory since it only first appears at two loop order and is large because it does not vanish for equal quark doublet masses, unlike the one loop term. We estimate that perturbation theory is useful for $m_Q\simeq 600\mathrm{GeV}$ but begins to become marginal for $m_Q\gtrsim 900\mathrm{GeV}$. The results apply directly to BSM4 models that retain the SM Higgs sector but must be reevaluated for non-SM Higgs sectors.

In order to relax the Landau pole constraint on “$\lambda$,” which is a coupling constant between a singlet $S$ and the minimal supersymmetric standard model (MSSM) Higgs, $\lambda S{h}_u{h}_d$ in the next-to MSSM, and also maintains the gauge coupling unification, we consider perturbative U(1) gauge extensions of the next-to MSSM. For relatively strong U(1) gauge interactions down to low energies, we assign U(1) charges only to the Higgs and the third family of the chiral matter among the MSSM superfields. In the $\mathrm{U}(1{)}_Z$ $[\mathrm{U}(1{)}_Z\times \mathrm{U}(1{)}_X]$ extension, the low-energy value of $\lambda$ can be lifted up to 0.85–0.95 [0.9–1.0], depending on the employed charge normalizations, when $\lambda$ and the new gauge couplings are required not to blow up below the ${10}^{16}\mathrm{GeV}$ energy scale. The introduction of extra vectorlike superfields can induce the desired Yukawa couplings for the first two families of the chiral matter. We also discuss various phenomenological constraints associated with extra U(1) breaking.

We develop and demonstrate techniques needed to compute the long distance contribution to the $K_L-K_S$ mass difference, $\Delta M_K$, in lattice QCD and carry out a first, exploratory calculation of this fundamental quantity. The calculation is performed on $2+1$ flavor, domain wall fermion, ${16}^3\times 32$ configurations with a 421 MeV pion mass and an inverse lattice spacing $1/a=1.73\mathrm{GeV}$. We include only current-current operators and drop all disconnected and double penguin diagrams. The short distance part of the mass difference in a $2+1$ flavor calculation contains a quadratic divergence cut off by the lattice spacing. Here, this quadratic divergence is eliminated through the Glashow-Iliopoulos-Maiani mechanism by introducing a valence charm quark. The inclusion of the charm quark makes the complete calculation accessible to lattice methods provided the discretization errors associated with the charm quark can be controlled. The long distance effects are discussed for each parity channel separately. While we can see a clear signal in the parity odd channel, the signal to noise ratio in the parity even channel is exponentially decreasing as the separation between the two weak operators increases. We obtain a mass difference $\Delta M_K$ which ranges from $6.58(30)\times {10}^{-12}\mathrm{MeV}$ to $11.89(81)\times {10}^{-12}\mathrm{MeV}$ for kaon masses varying from 563 to 839 MeV. Extensions of these methods are proposed which promise accurate results for both $\Delta M_K$ and ${ϵ}_K$, including long distance effects.

The one-loop level mediated $t\to c\gamma$ decay is analyzed in the framework of 331 models, which are based on the $S{U}_L(3)\times U_X(1)$ gauge symmetry and require that the quark families transform differently in order to cancel anomalies, thereby inducing three-level flavor-changing neutral currents mediated by an extra neutral gauge boson $Z^{\prime }$ and a neutral scalar boson $\varphi$. These models also predict new charged gauge and scalar bosons, together with three new quarks, which can be exotic (with electric charges of $-4/3e$ and $5/3e$) or standard-model-like. Apart from the contribution of the $W$ boson, the $t\to c\gamma$ decay receives contributions induced by the extra gauge boson and the neutral scalar boson, which are generic for 331 models. In the so-called minimal 331 model, there are additional contributions from the new charged gauge and scalar bosons accompanied by the exotic quarks. We present analytical results for the most general $t\to c\gamma$ amplitude in terms of transcendental functions. For the numerical analysis we focus on the minimal 331 model: the current bounds on the model parameters are examined and a particular scenario is discussed in which the corresponding branching ratio could be of the order of ${10}^{-6}$, with the dominant contributions arising from the charged gauge bosons and a relatively light neutral scalar boson with flavor-changing couplings, whereas the $Z^{\prime }$ contribution would be of the order of ${10}^{-9}$ for $m_{Z^{\prime }}>2\mathrm{TeV}$. However, a further suppression could be expected due to a potential suppression of the values of the flavor-changing coupling constants. Under the same assumptions, in 331 models without exotic quarks, the $t\to c\gamma$ branching ratio would receive the dominant contribution from the neutral scalar boson, which could be of the order of ${10}^{-7}$ for a Higgs mass of a few hundreds of GeVs.