A generalized two-brane Randall-Sundrum warped braneworld model has solutions of the warp factor for both positive or negative cosmological constant on the visible 3-brane which can resolve the naturalness problem in connection with the fine-tuning of Higgs mass in the standard model of elementary particles. To explore the location of the standard model fermions in such a generalized warped model, we, in this work, determine the dependence of the localization profile of a bulk fermion on the brane cosmological constant brane tension and the bulk fermion mass. Our results reveal that for a positive and small value of the induced cosmological constant a bulk fermion is localized close to the brane. On the other hand for a visible brane with negative cosmological constant and positive tension, the fermions are localized inside the bulk leading to phenomenologically interesting possibilities.

Modeling glueballs as bound states of transverse constituent gluons allows to understand the main features of the lattice QCD glueball spectrum. In particular it has been shown in previous works that the lightest $C$-even glueballs can be seen as bound states of two transverse constituent gluons interacting via a funnel potential. In the present study we show that such an effective potential emerges from the available lattice QCD data. Starting from the scalar glueball mass and wave function computed in lattice QCD, we indeed compute the equivalent local potential between two transverse constituent gluons in the scalar channel and show that it is compatible with a funnel shape, where standard values of the parameters are used and where a negative constant has to be added to reproduce the absolute height of the potential. Such a constant could be related to instanton-induced effects in glueballs.

We construct a weakly coupled, renormalizable ultraviolet completion of the littlest Higgs model with $T$ parity (LHT), based on an $SU(5)\times SU(2)\times U(1)$ gauge theory with a discrete $Z_2$ symmetry. Our model reproduces the complete structure of the LHT below the 10 TeV scale, including the collective symmetry-breaking mechanism which solves the little hierarchy problem. The model is manifestly free of anomalies, including both gauge/gravitational anomalies and anomalies involving $T$ parity. At the TeV scale, the model contains additional states not present in the LHT. We estimate the impact of these states on precision electroweak observables, and show that the model is realistic. We also discuss how our model can be embedded into a supersymmetric theory or a five-dimensional setup with a warped extra dimension, stabilizing the hierarchy between the 10 TeV and the Planck scale.

The inert doublet model is a minimal extension of the standard model introducing an additional SU(2) doublet with new scalar particles that could be produced at accelerators. While there exists no LEP II analysis dedicated for these inert scalars, the absence of a signal within searches for supersymmetric neutralinos can be used to constrain the inert doublet model. This translation however requires some care because of the different properties of the inert scalars and the neutralinos. We investigate what restrictions an existing DELPHI Collaboration study of neutralino pair production can put on the inert scalars and discuss the result in connection with dark matter. We find that although an important part of the inert doublet model parameter space can be excluded by the LEP II data, the lightest inert particle still constitutes a valid dark matter candidate.

We explore the use of polarized $e^{+}/e^{-}$ beams and/or the information on final state decay lepton polarizations in probing the interaction of the Higgs boson with a pair of vector bosons. A model independent analysis of the process $e^{+}{e}^{-}\to f\overline{f}H$, where $f$ is any light fermion, is carried out through the construction of observables having identical properties under the discrete symmetry transformations as different individual anomalous interactions. This allows us to probe an individual anomalous term independent of the others. We find that initial state beam polarization can significantly improve the sensitivity to $CP$-odd couplings of the $Z$ boson with the Higgs boson ($ZZH$). Moreover, an ability to isolate events with a particular $\tau$ helicity, with even 40% efficiency, can improve sensitivities to certain $ZZH$ couplings by as much as a factor of 3. In addition, the contamination from the $ZZH$ vertex contributions present in the measurement of the trilinear Higgs-$W$ ($WWH$) couplings can be reduced to a great extent by employing polarized beams. The effects of initial state radiation and beamstrahlung, which can be relevant for higher values of the beam energy are also included in the analysis.

One possible extension of the standard model scalar sector includes $SU(2{)}_L$ doublet scalars that are color octets rather than singlets. We focus on models in which the couplings to fermions are consistent with the principle of minimal flavor violation, in which case these color-octet scalars couple most strongly to the third generation of quarks. When the Yukawa coupling of color-octet scalars to standard model fermions is less than unity, these states can live long enough to bind into color-singlet spin-0 hadrons, which we call octetonia. In this paper, we consider the phenomenology of octetonia at the Large Hadron Collider. Predictions for their production via gluon-gluon fusion and their two-body decays into standard model gauge bosons, Higgs bosons, and $\overline{t}t$ are presented.

We investigate the longitudinal $WW$ scattering in models of dynamical electroweak symmetry breaking featuring a spin-one axial and vector state and a composite Higgs boson. We also investigate the effects of a composite spin-two state which has the same properties of a massive graviton. Any model of dynamical electroweak symmetry breaking will feature, depending on the dynamics, some or all of these basic resonances as part of the low energy spectrum. We suggest how to take limits in the effective Lagrangian parameter space to reproduce the dynamics of different types of underlying gauge theories, from the traditional technicolor models to the newest ones featuring nearly conformal dynamics. We study the direct effects of a light composite Higgs boson and the indirect ones stemming from the presence of a light axial resonance on the longitudinal $WW$ scattering.

In this work we study the $e^{+}{e}^{-}\to \varphi K^{+}{K}^{-}$ reaction. The leading order electromagnetic contributions to this process involve the ${\gamma }^{*}\varphi K^{+}{K}^{-}$ vertex function with a highly virtual photon. We calculate this function at low energies using $R\chi PT$ supplemented with the anomalous term for the $V{V}^{\prime }P$ interactions. Tree-level contributions involve the kaon form factors and the $K^{*}K$ transition form factors. We improve this result, valid for low photon virtualities, replacing the lowest order terms in the kaon form factors and $K^{*}K$ transition form factors by the form factors as obtained in $U\chi PT$ in the former case and the ones extracted from recent data on $e^{+}{e}^{-}\to K{K}^{*}$ in the latter case. We calculate rescattering effects which involve meson-meson amplitudes. The corresponding result is improved using the unitarized meson-meson amplitudes containing the scalar poles instead of the lowest order terms. Using the BABAR value for $\mathrm{BR}(X\to \varphi f_0)\Gamma (X\to e^{+}{e}^{-})$, we calculate the contribution from intermediate $X(2175)$. A good description of data is obtained in the case of destructive interference between this contribution and the previous ones, but more accurate data on the isovector $K^{*}K$ transition form factor is required in order to exclude contributions from an intermediate isovector resonance to $e^{+}{e}^{-}\to \varphi K^{+}{K}^{-}$ around 2.2 GeV.

We estimate the $CP$ asymmetry $A_{CP}(q^2)$ in the decays $B\to X_s{\mu }^{+}{\mu }^{-}$ and $B\to X_d{\mu }^{+}{\mu }^{-}$ in the standard model (SM) with an additional fourth generation. We use a parametrization that allows us to explore the complete parameter space of the $4\times 4$ quark mixing matrix, and constrain these parameters from the current data on $B$ decays. We find that the enhancement in $A_{CP}(q^2)$ depends strongly on the mass of the $t^{\prime }$, the up-type quark in the fourth generation. For $m_{t^{\prime }}$ around 400 GeV, the $CP$ asymmetry in the high-$q^2$ region ($q^2>14.4{\mathrm{GeV}}^2$) can be enhanced by more than an order of magnitude for $B\to X_s{\mu }^{+}{\mu }^{-}$ and up to a factor of 6 for $B\to X_d{\mu }^{+}{\mu }^{-}$. There is no enhancement in the low-$q^2$ region ($1<q^2<6{\mathrm{GeV}}^2$). With increasing $m_{t^{\prime }}$, $A_{CP}(q^2)$ in the high-$q^2$ (low-$q^2$) region first decreases (increases) and then saturates at a value a few times the SM prediction. In the high-$q^2$ region of $B\to X_s{\mu }^{+}{\mu }^{-}$, this saturation value may be up to 25 times the SM expectation.

New data on the decays of the charmed particles $D^0$, $D^{+}$, and $D_s$ to $PV$ final states consisting of a light pseudoscalar meson $P$ and a light vector meson $V$ are analyzed. Following the same methods as in a previous analysis of $D\to PP$ decays, one can test flavor symmetry, extract key amplitudes, and obtain information on relative strong phases. Analyses are performed for Cabibbo-favored decays and then extended to predict properties of singly and doubly Cabibbo-suppressed processes.

We analyze the electromagnetic pion and kaon form factor by including radiative and higher-twist effects within the framework of resummed perturbative QCD in the spacelike region. We focus on the transition from the perturbative to nonperturbative behavior in the phenomenological intermediate-energy regime. Using a modified “$k_T$” factorization scheme with transverse degrees of freedom, we evaluate the nonperturbative soft contributions as distinct from the hard contributions, ensuring no double counting via the Ward identity at $Q^2=0$. The soft contributions are obtained via local quark-hadron duality, while the hard contributions rest on the well-known collinear factorization theorem using model wave functions with modified Brodsky-Huang-Lepage–type ansatz and distribution amplitudes derived from light-cone QCD sum rules. Our analysis shows that the perturbative hard part prevails for large $Q^2$ beyond $50–100{\mathrm{GeV}}^2$, while for low and moderate momentum transfers below $10–16{\mathrm{GeV}}^2$, the soft contributions dominate over the hard part. Thus, we demonstrate the importance of including the soft contributions for explaining the experimental form-factor data.

We suggest a hybrid seesaw model where relatively light right-handed neutrinos give no contribution to neutrino mass matrix due to a special symmetry. This allows their Yukawa couplings to the standard model particles to be relatively strong, so that the standard model Higgs boson can decay dominantly to a left- and a right-handed neutrino, leaving another stable right-handed neutrino as cold dark matter. In our model neutrino masses arise via the type-II seesaw mechanism, the Higgs triplet scalars being also responsible for the generation of the matter-antimatter asymmetry via the leptogenesis mechanism.

When gauged cosmic strings form in a symmetry-breaking phase transition, the gauge field configuration at the time becomes imprinted in the spatial string distribution by the flux trapping mechanism. Causality and flux conservation suggest that quantum and thermal gauge field fluctuations give rise to long-range super-horizon correlations in the string network. Classical field theory simulations in the Abelian Higgs model confirm this finding. In contrast, the Kibble-Zurek mechanism, which most cosmic string studies are based on, only gives rise to short-distance, subhorizon correlations. These results may have implications for cosmology, and it may also be possible to test them in superconductor experiments.

Cosmologists have suggested a number of intriguing hypotheses for the origin of the “WMAP cold spot,” the coldest extended region seen in the cosmic microwave background (CMB) sky, including a very large void and a collapsing texture. Either hypothesis predicts a distinctive CMB lensing signal. We show that the upcoming generation of high resolution CMB experiments such as Atacama Cosmology Telescope and the South Pole Telescope should be able to detect the signatures of either textures or large voids. If either signal is detected, it will have profound implications for cosmology.

While there is plentiful evidence in all fronts of experimental cosmology for the existence of a nonvanishing dark energy (DE) density ${\rho }_D$ in the Universe, we are still far away from having a fundamental understanding of its ultimate nature and of its current value, not even of the puzzling fact that ${\rho }_D$ is so close to the matter energy density ${\rho }_M$ at the present time (i.e. the so-called “cosmic coincidence” problem). The resolution of some of these cosmic conundrums suggests that the DE must have some (mild) dynamical behavior at the present time. In this paper, we examine some general properties of the simultaneous set of matter and DE perturbations $(\delta {\rho }_M,\delta {\rho }_D)$ for a multicomponent DE fluid. Next we put these properties to the test within the context of a nontrivial model of dynamical DE (the $\Lambda \mathrm{XCDM}$ model) which has been previously studied in the literature. By requiring that the coupled system of perturbation equations for $\delta {\rho }_M$ and $\delta {\rho }_D$ has a smooth solution throughout the entire cosmological evolution, that the matter power spectrum is consistent with the data on structure formation, and that the “coincidence ratio” $r={\rho }_D/{\rho }_M$ stays bounded and not unnaturally high, we are able to determine a well-defined region of the parameter space where the model can solve the cosmic coincidence problem in full compatibility with all known cosmological data.

The continuum Yang-Mills functional integral within the first order formalism and in Coulomb gauge is studied. In particular, the temporal zero modes of the Faddeev-Popov operator are explicitly accounted for. It is shown that the treatment of these zero modes results in the constraint that the total color charge of the system vanishes at all times. Further, it is argued that the functional integral is effectively fully gauge fixed once Gauss’ law has been resolved in Coulomb gauge.

Two one-parameter families of twists providing $\kappa$-Minkowski $*$ product deformed spacetime are considered: Abelian and Jordanian. We compare the derivation of quantum Minkowski space from two perspectives. The first one is the Hopf module algebra point of view, which is strictly related with Drinfeld’s twisting tensor technique. The other one relies on an appropriate extension of “deformed realizations” of nondeformed Lorentz algebra by the quantum Minkowski algebra. This extension turns out to be de Sitter Lie algebra. We show the way both approaches are related. The second path allows us to calculate deformed dispersion relations for toy models ensuing from different twist parameters. In the Abelian case, one recovers $\kappa$-Poincaré dispersion relations having numerous applications in doubly special relativity. Jordanian twists provide a new type of dispersion relations which in the minimal case (related to Weyl-Poincaré algebra) takes an energy-dependent linear mass deformation form.

In this paper we use the second order formalism of Hartle to study slowly and rigidly rotating stars with focus on the quadrupole moment of the object. The second order field equations for the interior fluid are solved numerically for different classes of possible equations of state and these solutions are then matched to a vacuum solution that includes the general asymptotically flat axisymmetric metric to second order, using the Darmois-Israel procedure. For these solutions we find that the quadrupole moment differs from that of the Kerr metric, as has also been found for some equations of state in other studies. Further we consider the post-Minkowskian limit analytically. In the paper we also illustrate how the relativistic multipole moments can be calculated from a complex gravitational potential.

We describe “small bodies” in a nonmetric gravity theory previously studied by this author. The main dynamical field of the theory is a certain triple of 2-forms rather than the metric, with only the spacetime conformal structure, not metric, being canonically defined. The theory is obtained from general relativity in Plebanski formulation by adding to the action a certain potential. Importantly, the modification does not change the number of propagating degrees of freedom as compared to general relativity. We find that small bodies move along geodesics of a certain metric that is constructed with the help of a new potential function that appears in the matter sector. We then use the small body results to formulate a prescription for coupling the theory to general stress-energy tensor. In its final formulation the theory takes an entirely standard form, with matter propagating in a metric background and only the matter-gravity coupling and the gravitational dynamics being modified. This completes the construction of the theory and opens way to an analysis of its physical predictions.