We use the recently proposed Kaluza-Klein (KK) reduction over the time dimension, within an effective field theory (EFT) approach, to calculate the next-to-leading order gravitational spin1-spin2 interaction between two spinning compact objects. It is shown here that to next-to-leading order in the spin1-spin2 interaction, the reduced KK action within the stationary approximation is sufficient to describe the gravitational interaction, and that it simplifies calculation substantially. We also find here that the gravitomagnetic vector field defined within the KK decomposition of the metric mostly dominates the mediation of the interaction. Our results coincide with those calculated in the Arnowitt-Deser-Misner Hamiltonian formalism, and we provide another explanation for the discrepancy with the result previously derived within the EFT approach, thus demonstrating clearly the equivalence of the Arnowitt-Deser-Misner Hamiltonian formalism and the EFT action approach.

We revisit the issue of the limit on the scale of left-right symmetry breaking. We focus on the minimal $\mathrm{SU}(2{)}_L\times \mathrm{SU}(2{)}_R\times \mathrm{U}(1{)}_{B-L}$ gauge theory with the seesaw mechanism and discuss the two possibilities of defining left-right symmetry as parity or charge conjugation. In the commonly adopted case of parity, we perform a complete numerical study of the quark mass matrices and the associated left and right mixing matrices without any assumptions usually made in the literature about the ratio of vacuum expectation values. We find that the usual lower limit on the mass of the right-handed gauge boson from the $K$ mass difference, $M_{W_R}>2.5\mathrm{TeV}$, is subject to a possible small reduction due to the difference between right and left Cabibbo angles. In the case of charge conjugation the limit on $M_{W_R}$ is somewhat more robust. However, the more severe bounds from $CP$-violating observables are absent in this case. In fact, the free phases can also resolve the present mild discrepancy between the standard model and $CP$ violation in the $B$ sector. Thus, even in the minimal case, both charged and neutral gauge bosons may be accessible at the Large Hadron Collider with spectacular signatures of lepton number violation.

We propose a simple extension of the standard model (SM) by adding an extra $U(1)$ symmetry which is hidden from the SM sector. Such a hidden $U(1)$ has not been considered before, and its existence at the TeV scale can be explored at the LHC. This hidden $U(1)$ does not couple directly to the SM particles, and couples only to new $SU(2{)}_L$ singlet exotic quarks and singlet Higgs bosons, and is broken at the TeV scale. The dominant signals at the high-energy hadron colliders are multilepton and multi-$b$-jet final states with or without missing energy. We calculate the signal rates as well as the corresponding standard model background for these final states. A very distinctive signal is 6 high $p_T$ $b$-jets in the final state with no missing energy. For a wide range of the exotic quarks masses the signals are observable above the background at the LHC.

We study muon pair production $e^{+}{e}^{-}\to {\mu }^{+}{\mu }^{-}$ in the noncommutative (NC) extension of the standard model using the Seiberg-Witten maps of this to the second order of the noncommutative parameter ${\Theta }_{\mu \nu }$. Using $\mathcal{O}({\Theta }^2)$ Feynman rules, we find the $\mathcal{O}({\Theta }^4)$ cross section (with all other lower order contributions simply cancelled) for the pair production. The momentum dependent $\mathcal{O}({\Theta }^2)$ NC interaction significantly modifies the cross section and angular distributions which are different from the commuting standard model. We study the collider signatures of the space-time noncommutativity at the International Linear Collider (ILC) and find that the process $e^{+}{e}^{-}\to {\mu }^{+}{\mu }^{-}$ can probe the NC scale $\Lambda$ in the range 0.8–1.0 TeV for typical ILC energy ranges.

We present a calculation of $\mathcal{O}({\alpha }_s)$ contributions to the process of $t$-channel single-top production and decay, which include virtual and real corrections arising from the interference of the production and decay subprocesses. The calculation is organized as a simultaneous expansion of the matrix elements in the couplings ${\alpha }_{\mathrm{ew}}$, ${\alpha }_s$ and the virtuality of the intermediate top quark, $(p_t^2-m_t^2)/m_t^2\sim {\Gamma }_t/m_t$, and extends earlier results beyond the narrow-width approximation.

It has been proposed that microwave cavities can be used in a photon regeneration experiment to search for hidden sector photons. Using two isolated cavities, the presence of hidden sector photons could be inferred from a “light shining through a wall” phenomenon. The sensitivity of the experiment has strong a dependence on the geometric construction and electromagnetic mode properties of the two cavities. In this paper we perform an in-depth investigation to determine the optimal setup for such an experiment. We also describe the results of our first microwave cavity experiment to search for hidden sector photons. The experiment consisted of two cylindrical copper cavities stacked axially inside a single vacuum chamber. At a hidden sector photon mass of $37.78\mu \mathrm{eV}$ we place an upper limit on the kinetic mixing parameter $\chi =2.9\times {10}^{-5}$. Whilst this result lies within already established limits our experiment validates the microwave cavity “light shining through a wall” concept. We also show that the experiment has great scope for improvement, potentially able to reduce the current upper limit on the mixing parameter $\chi$ by several orders of magnitude.

In the present paper, we study the scalar sector of the quasinormal modes of charged general relativistic, static, and spherically symmetric black holes coupled to nonlinear electrodynamics and embedded in a class of scalar-tensor theories. We find that for a certain domain of the parametric space, there exists unstable quasinormal modes. The presence of instabilities implies the existence of scalar-tensor black holes with primary hair that bifurcate from the embedded general relativistic black-hole solutions at critical values of the parameters corresponding to the static zero modes. We prove that such scalar-tensor black holes really exist by solving the full system of scalar-tensor field equations for the static, spherically symmetric case. The obtained solutions for the hairy black holes are nonunique, and they are in one-to-one correspondence with the bounded states of the potential governing the linear perturbations of the scalar field. The stability of the nonunique hairy black holes is also examined, and we find that the solutions for which the scalar field has zeros are unstable against radial perturbations. The paper ends with a discussion of possible formulations of a new classification conjecture.

Within the covariant formulation of light-front dynamics, we calculate the state vector of a physical fermion in the Yukawa model. The state vector is decomposed in Fock sectors and we consider the first three ones: the single constituent fermion, the constituent fermion coupled to one scalar boson, and the constituent fermion coupled to two scalar bosons. This last three-body sector generates nontrivial and nonperturbative contributions to the state vector, which are calculated numerically. Field-theoretical divergences are regularized using Pauli-Villars fermion and boson fields. Physical observables can be unambiguously deduced using a systematic renormalization scheme we have developed previously. As a first application, we consider the anomalous magnetic moment of the physical fermion.

Extra vectorlike matter with both electroweak-singlet masses and large Yukawa couplings can significantly raise the lightest Higgs boson mass in supersymmetry through radiative corrections. I consider models of this type that involve a large Yukawa coupling between weak isotriplet and isodoublet chiral supermultiplets. The particle content can be completed to provide perturbative gauge coupling unification, in several different ways. The impact on precision electroweak observables is shown to be acceptably small, even if the new particles are as light as the current experimental bounds of order 100 GeV. I study the corrections to the lightest Higgs boson mass, and discuss the general features of the collider signatures for the new fermions in these models.

We evaluate the dressed Polyakov loop for hot quark matter in strong magnetic field. To compute the finite temperature effective potential, we use the Polyakov extended Nambu–Jona-Lasinio model with eight-quark interactions taken into account. The bare quark mass is adjusted in order to reproduce the physical value of the vacuum pion mass. Our results show that the dressed Polyakov loop is very sensitive to the strength of the magnetic field, and it is capable to capture both the deconfinement crossover and the chiral crossover. Additionally, we self-consistently compute the phase diagram of the model. We find a tiny split of the two aforementioned crossovers as the strength of the magnetic field is increased. Concretely, for the largest value of magnetic field investigated here, $eB=19m_{\pi }^2$, the split is of the order of 10%. A qualitative comparison with other effective models and recent lattice results is also performed.

We explore the discovery potential of doubly charged Higgs bosons (${\xi }^{\pm \pm }$) at the CERN Large Hadron Collider (LHC). For moderate values of the coupling constants in the original Type-II seesaw model, these doubly charged Higgs bosons are not accessible at any present or near future collider experiments. In a gauged $B-L$ symmetric model we introduce two triplet scalars to execute a variant of type-II seesaw at the TeV scale. This leads to a clear like-sign dilepton signal in the decay mode of ${\xi }^{\pm \pm }$ for a small vacuum expectation value ($\lesssim {10}^5\mathrm{eV}$) of the triplet scalar $\xi =({\xi }^{++},{\xi }^{+},{\xi }^0)$ of mass $\lesssim 1\mathrm{TeV}$. To be specific, for a mass range of 200–1000 GeV of ${\xi }^{\pm \pm }$, the like-sign dilepton signal can be detected at CERN LHC at a center of mass energy 14 TeV with an integrated luminosity, say, $\gtrsim 30{\mathrm{fb}}^{-1}$. The same analysis is also pursued with center of mass energies 7 TeV and 10 TeV as well. We also comment on the decay mode of singly charged scalars and the neutral $B-L$ gauge boson in this model.

A measurement of the $t\overline{t}$ production cross section in $p\overline{p}$ collisions at $\sqrt{\mathrm{s}}=1.96\mathrm{TeV}$ using events with two leptons, missing transverse energy, and jets is reported. The data were collected with the CDF II detector. The result in a data sample corresponding to an integrated luminosity $2.8{\mathrm{fb}}^{-1}$ is ${\sigma }_{t\overline{t}}=6.27\pm 0.73(\mathrm{stat})\pm 0.63(\mathrm{syst})\pm 0.39(\mathrm{lum})\mathrm{pb}.$ for an assumed top mass of $175\mathrm{GeV}/c^2$.

We consider $\mathcal{N}=2$ supersymmetric QCD with the $\mathrm{U}(N)$ gauge group (with no Fayet-Iliopoulos term) and $N_f$ flavors of massive quarks deformed by the mass term $\mu$ for the adjoint matter, $\mathcal{W}=\mu {\mathcal{A}}^2$, assuming that $N\le N_f<2N$. This deformation breaks $\mathcal{N}=2$ supersymmetry down to $\mathcal{N}=1$. This theory supports non-Abelian flux tubes (strings) which are stabilized by $\mathcal{W}$. They are referred to as $F$-term stabilized strings. We focus on the studies of such strings in the vacuum in which $N$ squarks condense, at small $\mu$, so that the $Z_N$ strings preserve, in a sense, their Bogomol’nyi-Prasad-Sommerfield nature. The (s)quark masses are assumed to be nondegenerate. We calculate string tensions both in the classical and quantum regimes. Then we translate our results for the tensions in terms of the effective low-energy weighted $CP(N_f-1)$ model on the string world sheet. The bulk $\mu$ deformation makes this theory $\mathcal{N}=(0,2)$ supersymmetric heterotic weighted $CP(N_f-1)$ model in two dimensions. We find the deformation potential on the world sheet. This significantly expands the class of the heterotically deformed $CP$ models emerging on the string world sheet compared to that suggested by Edalati and Tong. Among other things, we show that nonperturbative quantum effects in the bulk theory are exactly reproduced by the quantum effects in the world-sheet theory.

We propose the most general modified first-order Hořava-Lifshitz gravity, whose action does not contain time derivatives higher than the second order. The Hamiltonian structure of this theory is studied in all the details in the case of the spatially-flat Friedmann-Robertson-Walker (FRW) space-time, demonstrating many of the features of the general theory. It is shown that, with some plausible assumptions, including the projectability of the lapse function, this model is consistent. As a large class of such theories, the modified Hořava-Lifshitz $F(R)$ gravity is introduced. The study of its ultraviolet properties shows that its $z=3$ version seems to be renormalizable in the same way as the original Hořava-Lifshitz proposal. The Hamiltonian analysis of the modified Hořava-Lifshitz $F(R)$ gravity shows that it is in general a consistent theory. The $F(R)$ gravity action is also studied in the fixed-gauge form, where the appearance of a scalar field is particularly illustrative. Then the spatially-flat FRW cosmology for this $F(R)$ gravity is investigated. It is shown that a special choice of parameters for this theory leads to the same equations of motion as in the case of traditional $F(R)$ gravity. Nevertheless, the cosmological structure of the modified Hořava-Lifshitz $F(R)$ gravity turns out to be much richer than for its traditional counterpart. The emergence of multiple de Sitter solutions indicates the possibility of unification of early-time inflation with late-time acceleration within the same model. Power-law $F(R)$ theories are also investigated in detail. It is analytically shown that they have a quite rich cosmological structure: early-/late-time cosmic acceleration of quintessence, as well as of phantom types. Also it is demonstrated that all the four known types of finite-time future singularities may occur in the power-law Hořava-Lifshitz $F(R)$ gravity. Finally, a covariant proposal for (renormalizable) $F(R)$ gravity within the Hořava-Lifshitz spirit is presented.

Non-Abelian gauge theory with a warped extra dimension is studied as a quantum field theory at an intermediate scale that is regarded as being much lower than the scale of the geometry stabilization and the Planck scale. Loop corrections for zero-mode vertices are diagrammatically calculable in perturbation at the intermediate scale. The contribution for each diagram can be compared to the correspondent in the four-dimensional theory. It is found that for a part of the contributions, the coefficient for the logarithmic scaling has the same value as the four-dimensional results. A viewpoint to treat corrections associated with higher-dimensional operators is also discussed.

A field in the vacuum state, which is in principle separable, can evolve to an entangled state in a dynamical gravitational collapse. We will study, quantify, and discuss the origin of this entanglement, showing that it could even reach the maximal entanglement limit for low frequencies or very small black holes, with consequences in micro-black hole formation and the final stages of evaporating black holes. This entanglement provides quantum information resources between the modes in the asymptotic future (thermal Hawking radiation) and those which fall to the event horizon. We will also show that fermions are more sensitive than bosons to this quantum entanglement generation. This fact could be helpful in finding experimental evidence of the genuine quantum Hawking effect in analog models.

We present the complete set of renormalization group equations at one loop for the nonexotic minimal $U(1)$ extension of the standard model (SM). It includes all models that are anomaly-free with the SM fermion content augmented by one right-handed neutrino per generation. We then pursue the numerical study of the pure $B-L$ model, deriving the triviality and vacuum stability bounds on an enlarged scalar sector comprising one additional Higgs singlet field with respect to the SM.

We study the phase diagram of strongly interacting matter in the framework of a nonlocal SU(2) chiral quark model which includes wave function renormalization and coupling to the Polyakov loop. Both nonlocal interactions based on the frequently used exponential form factor, and on fits to the quark mass and renormalization functions obtained in lattice calculations are considered. Special attention is paid to the determination of the critical points, both in the chiral limit and at finite quark mass. In particular, we study the position of the critical end point as well as the value of the associated critical exponents for different model parametrizations.

We study the $Z(4430{)}^{\pm }$ meson within a heavy hadron molecule interpretation where the $Z$ is considered as a bound state of a vector $D^{*}(2010)$ and an axial-vector $D_1(2420)$. We give predictions for the strong hidden-charm $Z(4430{)}^{\pm }\to {\pi }^{\pm }\psi$ and ${\pi }^{\pm }{\psi }^{\prime }$ decay widths and also study the radiative $Z^{\pm }(J^P=1^{-})\to {\pi }^{\pm }\gamma$ decay properties in a phenomenological Lagrangian approach. Our findings are qualitatively in line with the experimental observation that the ${\pi }^{\pm }{\psi }^{\prime }$ transition dominates over the ${\pi }^{\pm }\psi$ decay mode despite a smaller phase space. The width for the radiative mode ${\pi }^{\pm }\gamma$ is sizable, allowing possible detection in future experiments.

We present a two-flavor linear sigma model with global chiral symmetry and vector and axial-vector mesons. We calculate $\pi \pi$ scattering lengths and the decay widths of scalar, vector, and axial-vector mesons. It is demonstrated that vector and axial-vector meson degrees of freedom play an important role in these low-energy processes and that a reasonable theoretical description requires globally chirally invariant terms other than the vector-meson mass term. An important question for meson vacuum phenomenology is the quark content of the physical scalar $f_0(600)$ and $a_0(980)$ mesons. We investigate this question by assigning the quark-antiquark $\sigma$ and $a_0$ states of our model with these physical mesons. We show via a detailed comparison with experimental data that this scenario can describe all vacuum properties studied here except for the decay width of the $\sigma$, which turns out to be too small. We also study the alternative assignment $f_0(1370)$ and $a_0(1450)$ for the scalar mesons. In this case the decay width agrees with the experimental value, but the $\pi \pi$ scattering length $a_0^0$ is too small. This indicates the necessity to extend our model by additional scalar degrees of freedom.