We study the multiphoton decays of the Higgs boson from an effective Lagrangian for a system of electromagnetic and Higgs fields. We utilize a low-energy theorem to connect the above Lagrangian to the Heisenberg-Euler effective Lagrangian induced by charged particles that gain mass from interactions with the Higgs boson. In the standard model, only the $W^{\pm }$ gauge bosons and the top quark are relevant, and we compute their contributions to the effective couplings and the radiative decay widths of the Higgs boson up to six photons.

Generalized scaling in flavor neutrino masses $M_{ij}$ ($i$, $j=e$, $\mu$, $\tau$) expressed in terms of ${\theta }_{\mathrm{SC}}$ and the atmospheric neutrino mixing angle ${\theta }_{23}$ is defined by $M_{i\tau }/M_{i\mu }=-{\kappa }_i{t}_{23}$ ($i=e$, $\mu$, $\tau$) with ${\kappa }_e=1$, ${\kappa }_{\mu }=B/A$ and ${\kappa }_{\tau }=1/B$, where $t_{23}=\tan {\theta }_{23}$, $A={cos}^2{\theta }_{\mathrm{SC}}+{sin}^2{\theta }_{\mathrm{SC}}{t}_{23}^4$ and $B={cos}^2{\theta }_{\mathrm{SC}}-{sin}^2{\theta }_{\mathrm{SC}}{t}_{23}^2$. The generalized scaling ansatz predicts the vanishing reactor neutrino mixing angle ${\theta }_{13}=0$. It is shown that the minimal seesaw mechanism naturally implements our scaling ansatz. There are textures satisfying the generalized scaling ansatz that yield vanishing baryon asymmetry of the Universe (BAU). Focusing on these textures, we discuss effects of ${\theta }_{13}\ne 0$ to evaluate a $CP$-violating Dirac phase $\delta$ and BAU and find that BAU is approximately controlled by the factor ${sin}^2{\theta }_{13}\sin (2\delta -\varphi )$, where $\varphi$ stands for the $CP$-violating Majorana phase whose magnitude turns out to be at most 0.1.

We consider the most general $CP$-conserving renormalizable effective scalar potential involving two doublets plus one singlet Higgs and satisfying the electroweak gauge symmetry. After deriving the electroweak symmetry breaking conditions, we focus on special cases, characterized by specific symmetry properties and/or relations to supersymmetry-inspired extensions of the Standard Model [e.g., nearly minimal supersymmetric StandardModel (nMSSM), next-to-minimal supersymmetric Standard Model (NMSSM), $U(1{)}^{\prime }$ extended minimal supersymmetric Standard Model (UMSSM)]. We then investigate the question of the reconstruction of the potential parameters from the Higgs masses and mixing angles and show that in some specific cases, such as the one of an underlying NMSSM, an accuracy at the order of leading logarithms is achievable with minimal effort. We finally study a few phenomenological consequences for this latter model. More specifically, we consider how our parameter reconstruction modifies the outcome of two publicly available codes: micrOMEGAs and NMSSMTools. We observed noteworthy effects in regions of parameter space where Higgs-to-Higgs decays are relevant, impacting the collider searches for light Higgs states and the prediction of the dark matter relic density.

In supersymmetric models, a large average stop mass $M_S$ is well known to both boost the lightest Higgs boson mass $m_h$ and also make radiative electroweak symmetry breaking unnaturally tuned. The case of “maximal mixing,” where the stop trilinear mixing term $A_t$ is set to give $A_t^2/M_S^2=6$, allows the stops to be as light as possible for a given $m_h$. Here we make the distinction between minimal $M_S$ and optimal naturalness, showing that the latter occurs for less-than-maximal mixing. Lagrange-constrained optimization reveals that the two coincide closely in the Minimal Supersymmetric Standard Model (MSSM)—optimally we have $5<A_t^2/M_S^2<6$. We discuss why the two are not generally expected to coincide beyond the MSSM, and explain that even within the MSSM, different models should not be compared based on the $M_S$ necessary to achieve a given $m_h$. The splitting between the two stop-mass eigenvalues $m_{{\tilde{t}}_2}-m_{{\tilde{t}}_1}$ is shown to be unconstrained by naturalness considerations.

We reconsider constraints on the eigenvalue density of the Dirac operator in the chiral-symmetric phase of two-flavor QCD at finite temperature. To avoid possible ultraviolet divergences, we work on a lattice, employing the overlap Dirac operator, which ensures the exact “chiral” symmetry at finite lattice spacings. Studying multipoint correlation functions in various channels and taking their thermodynamical limit (and then taking the chiral limit), we obtain stronger constraints than those found in the previous studies: both the eigenvalue density at the origin and its first and second derivatives vanish in the chiral limit of two-flavor QCD. In addition, we show that the axial U(1) anomaly becomes invisible in susceptibilities of scalar and pseudoscalar mesons, suggesting that the second-order chiral phase transition with the $O(4)$ scaling is not realized in two-flavor QCD. Possible lattice artifacts when the nonchiral lattice Dirac operator is employed are briefly discussed.

We study the role of low momentum transfer (soft) interactions between high transverse momentum heavy particles and beam remnants (spectators) in hadronic collisions. Such final state interactions are power suppressed for single-particle inclusive cross sections whenever that particle is accompanied by a recoiling high-$p_T$ partner whose momentum is not fixed. An example is the single-top inclusive cross section in top-pair production. Final state soft interactions in multiparticle inclusive cross sections, including transverse momentum distributions, however, produce leading-power corrections in the absence of hard recoiling radiation. Nonperturbative corrections due to scattering from spectators are generically suppressed by powers of $\Lambda /p_T^{\prime }$, where $\Lambda$ is a hadronic scale and $p_T^{\prime }$ is the largest transverse momentum of radiation recoiling against the particles whose momenta are observed.

Event rates for ${\nu }_e$ and ${\overline{\nu }}_e$ appearance oscillations reported by the MINOS and T2K long baseline experiments are used to set constraints on the strength of the nonstandard interaction ${ϵ}_{e\tau }{V}_e$ matter potential. The ranges allowed for the magnitude and phase of ${ϵ}_{e\tau }$ are delineated for scenarios wherein (i) other nonstandard interactions for neutrinos propagating through the terrestrial crust are negligible and (ii) the real-valued, flavor-diagonal couplings ${ϵ}_{ee}$ and ${ϵ}_{\tau \tau }$ are also operative. Our analysis makes use of accurate analytic forms for the ${\nu }_e$ amplitude $\mathcal{A}({\nu }_{\mu }\to {\nu }_e)$ describing neutrino oscillation in constant-density matter in the presence of ${ϵ}_{e\tau }$, ${ϵ}_{ee}$ and ${ϵ}_{\tau \tau }$ nonstandard interactions.

We present a complete update of the analysis of ${\nu }_e$ and ${\overline{\nu }}_e$ disappearance experiments in terms of neutrino oscillations in the framework of $3+1$ neutrino mixing, taking into account the Gallium anomaly, the reactor anomaly, solar neutrino data, and ${\nu }_e\mathrm{C}$ scattering data. We discuss the implications of a recent ${}^{71}\mathrm{Ga}({}^3\mathrm{He},{}^3\mathrm{H}){}^{71}\mathrm{Ge}$ measurement which give information on the neutrino cross section in Gallium experiments. We discuss the solar bound on active-sterile mixing and present our numerical results. We discuss the connection between the results of the fit of neutrino oscillation data and the heavy neutrino mass effects in $\beta$-decay experiments (considering new Mainz data) and neutrinoless double-$\beta$ decay experiments (considering the recent EXO results).

On account of the new neutrino oscillation data signaling a nonzero value for the smallest mixing angle (${\theta }_z$), we present an explicit realization of the underlying $U(1)$ symmetry characterizing the maximal atmospheric mixing angle (${\theta }_y=\frac{\pi }{4}$) pattern with two degenerate masses but now with generic values of ${\theta }_z$. We study the effects of the form invariance with respect to $U(1)$, and/or $Z_3$, $Z_2$ subgroups, on the Yukawa couplings and the mass terms. Later on, we specify ${\theta }_z$ to its experimental best fit value ($\sim 8^o$), and impose the symmetry in an entire model which includes charged leptons, and many Higgs doublets or standard model singlet heavy scalars, to show that it can make room for the charged lepton mass hierarchies. In addition, we show for the non-tribimaximal value of ${\theta }_z\ne 0$ within a type-I seesaw mechanism enhanced with flavor symmetry that neutrino mass hierarchies can be generated. Furthermore, lepton/baryogenesis can be interpreted via a type-II seesaw mechanism within a setup meeting the flavor $U(1)$ symmetry.

We discuss the baryon in the holographic QCD framework and focus on the role of the bifundamental scalar field, realizing chiral symmetry breaking. We suggest the interpretation of a baryon as a dyonic instanton within the Atiyah-Manton-like approach for the flavor gauge group in the peculiar cylindrical ansatz in five-dimensional theory. Our approach provides the new mechanism of the stabilization of the baryon size.

We study $\mathrm{AdS}\times X$ null deformations arising as near horizon limits of D3-brane analogs of inhomogeneous plane waves. Restricting to normalizable deformations for the ${\mathrm{AdS}}_5$ case, these generically correspond in the dual field theory to super Yang-Mills states with light cone momentum density $T_{++}$ varying spatially, the homogeneous case studied in [K. Narayan, arXiv:1202.5935] corresponding to uniform $T_{++}$. All of these preserve some supersymmetry. Generically these inhomogeneous solutions exhibit analogs of horizons in the interior where a timelike Killing vector becomes null. From the point of view of $x^{+}$-dimensional reduction, the circle pinches off on these horizon loci in the interior. We discuss similar inhomogeneous solutions with asymptotically Lifshitz boundary conditions, as well as aspects of Lifshitz singularities in string constructions involving anti–de Sitter null deformations. We also briefly discuss holographic entanglement entropy for some of these.

Starting with a description of massive spin-2 particles in $D=4$ in terms of a mixed symmetry tensor $T_{[\mu \nu ]\rho }$ without a totally antisymmetric part ($T_{[[\mu \nu ]\rho ]}=0$), we obtain a dual model in terms of a nonsymmetric tensor $e_{\mu \nu }$. The model is of second order in derivatives, and its mass term ($e_{\mu \nu }{e}^{\nu \mu }+c{e}^2$) contains an arbitrary real parameter $c$. Remarkably, it is free of ghosts for any real value of $c$ and describes a massive spin-2 particle as expected from duality. The antisymmetric part $e_{[\mu \nu ]}$ plays the role of auxiliary fields, vanishing on shell. In the massless case the model describes a massless spin-2 particle without ghosts.

Recent investigations have shown that inflation can be driven by four-dimensional strongly interacting theories nonminimally coupled to gravity. We explore this paradigm further by considering composite inflation driven by orientifold field theories. The advantage of using these theories resides in the fact that at large number of colors they feature certain super Yang-Mills properties. In particular, we can use for inflation the bosonic part of the Veneziano-Yankielowicz effective theory. Furthermore, we include the $1/N$ as well as fermion mass corrections at the effective Lagrangian level allowing us to explore the effects of these corrections on the inflationary slow-roll parameters. Additionally, the orientifold field theory with fermionic matter transforming according to the two-index antisymmetric representation for three colors is QCD. Therefore, this model can be interpreted as a new nonminimally coupled QCD theory of inflation. The scale of composite inflation, for all the models presented here, is of the order of ${10}^{16}\mathrm{GeV}$. Unitarity studies of the inflaton scattering suggest that the cutoff of the model is at the Planck scale.

The Casimir force between parallel lines in a theory describing condensed vortices in a plane is determined. We make use of the relation between a Chern-Simons-Higgs model and its dualized version, which is expressed in terms of a dual gauge field and a vortex field. The dual model can have a phase of condensed vortices, and, in this phase, there is a mapping to a model of two noninteracting massive scalar fields from which the Casimir force is readily obtained. We also discuss the details concerning the boundary conditions required for the scalar fields and their association with those for the vectorial field. We show that this association is subtle for the case of the transformations considered.

We consider black holes in an “unsuitable box”: a finite cavity coupled to a thermal reservoir at a temperature different than the black hole’s Hawking temperature. These black holes are described by metrics that are continuous but not differentiable due to a conical singularity at the horizon. We include them in the Euclidean path integral sum over configurations, and analyze the effect this has on black hole thermodynamics in the canonical ensemble. Black holes with a small deficit (or surplus) angle may have a smaller internal energy or larger density of states than the nearby smooth black hole, but they always have a larger free energy. Furthermore, we find that the ground state of the ensemble never possesses a conical singularity. When the ground state is a black hole, the contributions to the canonical partition function from configurations with a conical singularity are comparable to the contributions from smooth fluctuations of the fields around the black hole background. Our focus is on highly symmetric black holes that can be treated as solutions of two-dimensional dilaton gravity models: examples include Schwarzschild, asymptotically anti–de Sitter, and stringy black holes.

We construct the rank-$n$ finite temperature logarithmic conformal field theory (LCFT) starting from the $n$-coupled scalar field theory in the Bañados-Teitelboim-Zanelli black hole background. Its zero temperature limit reduces to a rank-$n$ LCFT in the ${\mathrm{AdS}}_3$ background whose gravity dual is a polycritical gravity. We compute all two-point functions of a rank-$n$ finite temperature LCFT. Using the retarded Green’s functions on the boundary, we obtain quasinormal modes of scalar $A_n$ which satisfies the $2n$th order linearized equation. Furthermore, the absorption cross section of $A_n$ indicates a feature of ${ln}^{n-1}[\omega \ell ]$ correction to the Klein-Gordon mode.

Already more that 40 years ago, it has been suggested that because of the enormous mass densities in the cores of neutron stars, the hadrons in the centers of neutron stars may undergo a phase transition to deconfined quark matter. In this picture, neutron stars could contain cores made of pure (up, down, strange) quark matter which are surrounded by a mixed phase of quarks and hadrons. More than that, because of the competition between the Coulomb and the surface energies associated with the positively charged regions of nuclear matter and negatively charged regions of quark matter, the mixed phase may develop geometrical structures similarly to what is expected of the subnuclear liquid-gas phase transition. In this paper we restrict ourselves to considering the formation of rare phase blobs in the mixed quark-hadron phase. The influence of rare phase blobs on the thermal and transport properties of neutron star matter is investigated. The total specific heat $c_V$, thermal conductivity $\kappa$, and electron-blob bremsstrahlung neutrino emissivities ${ϵ}_{\nu ,\mathrm{BR}}$, of quark-hybrid matter are computed, and the results are compared with the associated thermal and transport properties of standard neutron star matter. Our results show that the contribution of rare phase blobs to the specific heat is negligibly small. This is different for the neutrino emissivity from electron-blob bremsstrahlung scattering, which turns out to be of the same order of magnitude as the total contributions from other bremsstrahlung processes for temperatures below about ${10}^8\mathrm{K}$.

We study junctions of vortices, or boojums, at the interface between color and hadronic superconducting/superfluid phases. This type of interface could be present in the interior of neutron stars, where an inner core made of quark matter in the color-flavor-locked phase is surrounded by an outer shell of superconducting protons and superfluid neutrons. We study the fate of magnetic (proton) and superfluid (neutron) vortices as they enter the color-flavor-locked phase. We find that proton vortices terminate on Dirac monopoles of the massless magnetic field, and magnetic fluxes of massive gauge field spread along the surface and are screened by surface superconducting currents. On the other hand, three neutron vortices join at a boojum and are split into three color-magnetic vortices with different color-magnetic fluxes canceled out in total. The color-magnetic vortices host confined color-magnetic monopoles when strange quark mass is taken into account. We also present a simple numerical model of the shape of the neutron boojum.

We study and analyze the recent observations of the top pair production $\sigma (p\overline{p}\to t\overline{t})$ at the Tevatron through flavor conserving and flavor violating channels via vector and tensor unparticles. The unparticle sector is considered with the possibility of being a color singlet or octet. The modified unparticle propagator is used to investigate the contribution of these unparticles to the observed $A_{\mathrm{FB}}^{t\overline{t}}$ (forward-backward asymmetry in top pair production) and the spin correlation at the Tevatron. We have also studied the impact of the flavor violating couplings of unparticles to the third generation quarks on (a) pair production of same sign tops/antitops $\sigma (p\overline{p}\to tt+\overline{t}\overline{t})$ at the Tevatron and (b) the partial top decay width for ${\Gamma }_{\mathcal{U}}(t\to u{\mathcal{U}}^V)$. We find that a large region of parameter space is consistent with the measurements of the $t\overline{t}$ production cross section, $A_{\mathrm{FB}}^{t\overline{t}}$, and spin correlation coefficient at the Tevatron, and we observe that the top decay width measurement constrains the flavor violating coupling of vector unparticles more severely than the same sign top/antitop production at the Tevatron. We also predict the best point set in the model parameter space for specific choices of $d_{\mathcal{U}}$ corresponding to ${\chi }_{\min }^2$, evaluated using the $m_{t\overline{t}}$ spectrum of $A_{\mathrm{FB}}^{t\overline{t}}$ from the data set of Run II of the Tevatron at the integrated luminosity $8.7{\mathrm{fb}}^{-1}$. Our results and analysis are consistent even with unparticle theories that have broken scale invariance, as long as the infrared cutoff scale is much less than the top pair production threshold.

The QCD quark cyclobutadiene (ringlike), a new color structure of a tetraquark system, is proposed and studied in the flux-tube model with a multibody confinement interaction. Numerical calculations show that the light tetraquark systems ($u$, $d$, $s$ only) with cyclobutadiene, diquark-antidiquark flux-tube structures have similar energies and they can be regarded as QCD isomeric compounds. The energies of some tetraquark states are close to the energies of some excited mesons, and so in the study of these mesons, the tetraquark components should be taken into account. There are also some meson states, $\sigma$, $\kappa (800)$, $f_0(980)$, $f_0(1500)$, ${\pi }_1(1400)$, ${\pi }_1(1600)$, $f_2(1430)$ and $K^{*}(1410)$, where tetraquark components might be dominant. The meson states with exotic quantum numbers are studied as the tetraquark states. The multibody confinement interaction reduces the energy of the tetraquark state in comparison with the usual additive two-body confinement interaction model.