We point out that chameleon field theories might reveal themselves as an afterglow effect in axionlike particle search experiments due to chameleon-photon conversion in a magnetic field. We estimate the parameter space which is accessible by currently available technology and find that afterglow experiments could constrain this parameter space in a way complementary to gravitational and Casimir force experiments. In addition, one could reach photon-chameleon couplings which are beyond the sensitivity of common laser polarization experiments. We also sketch the idea of a Fabry-Pérot cavity with chameleons which could increase the experimental sensitivity significantly.

We present the calculations of the next-to-leading order (NLO) QCD corrections to the inclusive total cross sections for the associated production of the $W^{\pm }{H}^{\mp }$ through $b\overline{b}$ annihilation in the minimal supersymmetric standard model at the CERN Large Hadron Collider. The NLO QCD corrections can either enhance or reduce the total cross sections, but they generally efficiently reduce the dependence of the total cross sections on the renormalization/factorization scale. The magnitude of the NLO QCD corrections is about 10% in most of the parameter space and can reach 15% in some parameter regions. We also show the Monte Carlo simulation results for the $2j+{\tau }_{\mathrm{jet}}+{\mathrm{p̸}}_T$ signature from the $W^{\pm }$ and the $H^{\mp }$ decays including the NLO QCD effects, and find an observable signal at a $5\sigma$ level in some parameter region of the minimal supergravity model.

Recently the CDF and D0 Collaborations observed several bottom baryons. In this work we perform a systematic study of the masses of bottom baryons up to $1/m_Q$ in the framework of heavy quark effective field theory using the QCD sum rule approach. The extracted chromo-magnetic splitting between the bottom baryon heavy doublet agrees well with the experimental data.

The vector dominance of the electromagnetic form factors both for mesons and baryons arises naturally in holographic QCD, where both the number of colors and the ’t Hooft coupling are taken to be very large, offering a bona-fide derivation of the notion of vector dominance. The crucial ingredient for this is the infinite tower of vector mesons in the approximations made which share features that are characteristic of the quenched approximation in lattice QCD. We approximate the infinite sum by contributions from the lowest four vector mesons of the tower which turn out to saturate the charge and magnetic moment sum rules within a few percent and compute them totally free of unknown parameters for momentum transfers $Q^2\lesssim 1{\mathrm{GeV}}^2$. We identify certain observables that can be reliably computed within the approximations and others that are not, and discuss how the improvement of the latter can enable one to bring holographic QCD closer to QCD proper.

The formalism of nonstandard four-fermion interactions provides a convenient, model-independent way of parametrizing a wide class of “new physics” scenarios. In this article, we study the performance of reactor and superbeam neutrino experiments in the presence of such nonstandard interactions (NSI). Because of interference between the standard and nonstandard amplitudes, sizeable effects are to be expected if the NSI parameters are close to their current upper limits. We derive approximate formulas for the relevant oscillation probabilities including NSI, and show how the leading effects can be understood intuitively even without any calculations. We will present a classification of all possible NSI according to their impact on reactor and superbeam experiments, and it will turn out that these experiments are highly complementary in terms of their sensitivity to the nonstandard parameters. The second part of the paper is devoted to detailed numerical simulations, which will demonstrate how a standard oscillation fit of the mixing angle ${\theta }_{13}$ may fail if experimental data is affected by NSI. We find that for some nonstandard terms, reactor and superbeam experiments would yield seemingly conflicting results, while in other cases, they may agree well with each other, but the resulting value for ${\theta }_{13}$ could be far from the true value. This offset may be so large that the true ${\theta }_{13}$ is even ruled out erroneously. In the last section of the paper, we demonstrate that reactor and superbeam data can actually establish the presence of nonstandard interactions. Throughout our discussion, we pay special attention to the impact of the complex phases, and of the near detectors.

This paper is dedicated to present model independent results for noncommutative quantum mechanics. We determine sufficient conditions for the convergence of the Born series and, in the sequel, unitarity is proved in full generality.

The spontaneous breaking of translational invariance in noncommutative self-interacting scalar field theory in two dimensions is investigated by effective action techniques. The analysis confirms the existence of the stripe phase, already observed in lattice simulations, due to the nonlocal nature of the noncommutative dynamics.

In the paper we investigate observational constraints on coupling to gravity constant parameter $\xi$ using distant supernovae SNIa data, baryon oscillation peak (BOP), the cosmic microwave background radiation (CMBR) shift parameter, and the $H(z)$ data set. We estimate the value of this parameter to constrain the extended quintessence models with nonminimally coupled to gravity phantom scalar field. The combined analysis of observational data favors a value of $\xi$ which lies in close neighborhood of the conformal coupling. While our estimations are model dependent they give rise to an indirect bound on the equivalence principle.

MeV particles have been advocated as dark matter (DM) candidates in different contexts. This hypothesis can be tested indirectly by searching for the standard model (SM) products of DM self-annihilations. As the signal from DM self-annihilations depends on the square of the DM density, we might expect a sizable flux of annihilation products from our galaxy. Neutrinos are the least detectable particles in the SM and a null signal in this channel would allow to set the most conservative bound on the total annihilation cross section. Here, we show that neutrino detectors with good energy resolution and low energy thresholds can not only set bounds on the annihilation cross section but actually test the hypothesis of the possible existence of MeV DM, i.e. test the values of the cross section required to explain the observed DM density. At present, the data in the (positron) energy interval [18–82] MeV of the Super-Kamiokande experiment is already able to put a very stringent bound on the annihilation cross section for masses between $\sim 15–130\mathrm{MeV}$. Future large experiments, like megaton water-Čerenkov or large scintillator detectors, will improve the present limits and, if MeV DM exists, would be able to detect it.

The set of equations for the two-particle Green’s functions in a nonequilibrium medium is derived in the diffusive approximation. Both the two- and single-particle Green’s functions are calculated when matter is in the ground state. It is shown that the Landau Fermi-liquid consideration is correct when the interaction between particles in matter is rather weak or when matter is not too dense. In the opposite cases the energy spectrum of the particles is rearranged so that the step in the momentum distribution of the particles disappears. The applicability of the Landau Fermi-liquid theory is established in the general case.

Volume stabilization in models with flat extra dimensions could follow from vacuum energy residing in the bulk when translational invariance is spontaneously broken. We study a simple toy model that exemplifies this mechanism which considers a massive scalar field with nontrivial boundary conditions at the end points of the compact space, and includes contributions from brane and bulk cosmological constants. We perform our analysis in the conformal frame where the radion field, associated with volume variations, is defined, and present a general strategy for building stabilization potentials out of those ingredients. We also provide working examples for the interval and the $T^n/Z_2$ orbifold configuration.

We give a complete classification of mass dimension-5 Lorentz-noninvariant interactions composed from the standard model fields, using the effective field theory approach. We identify different classes of Lorentz-violating operators, some of which are protected against transmutation to lower dimensions even at the loop level. Within each class of operators we determine a typical experimental sensitivity to the size of Lorentz violation.

It is by now well known that the Poincaré group acts on the Moyal plane with a twisted coproduct. Poincaré invariant classical field theories can be formulated for this twisted coproduct. In this paper we systematically study such a twisted Poincaré action in quantum theories on the Moyal plane. We develop quantum field theories invariant under the twisted action from the representations of the Poincaré group, ensuring also the invariance of the $S$-matrix under the twisted action of the group. A significant new contribution here is the construction of the Poincaré generators using quantum fields.

We study stellar configurations and the space-time around them in metric $f(R)$ theories of gravity. In particular, we focus on the polytropic model of the Sun in two specific cases: the $f(R)=R-{\mu }^4/R$ model and a model with a stabilizing higher order term $f(R)=R-{\mu }^4/R+\beta R^3/(3{\mu }^4)$. We show how the stellar configuration in the $f(R)$ theory can, by appropriate initial conditions, be selected to be equal to that described by the Lane-Emden equation and how a simple scaling relation exists between the solutions. We also derive the correct solution analytically near the center of the star in $f(R)$ theory. Previous analytical and numerical results are confirmed, indicating that the space-time around the Sun is incompatible with solar system constraints in the $f(R)=R-{\mu }^4/R$ model. Numerical work shows that stellar configurations, with a regular metric at the center, lead to ${\gamma }_{\mathrm{PPN}}\simeq 1/2$ outside the star for both models, i.e., the Schwarzschild–de Sitter space-time is not the correct vacuum solution for such configurations. This shows that even when one fine-tunes the initial conditions inside a star such that the mass of the effective scalar in the equivalent scalar-tensor theory is large, ${\gamma }_{\mathrm{PPN}}$ is still $1/2$ outside the star. Conversely, by selecting the Schwarzschild–de Sitter metric as the outside solution, or equivalently setting the mass of the effective scalar to be large outside the star, we find that the stellar configuration is unchanged but the metric is irregular at the center. The possibility of constructing a $f(R)$ theory compatible with the solar system experiments and possible new constraints arising from the radius-mass relation of stellar objects is discussed.

We study the properties and behavior of the quasipseudospherical and quasiplanar Szekeres models, obtain the regularity conditions, and analyze their consequences. The quantities associated with radius and mass in the quasispherical case must be understood in a different way for these cases. The models with pseudospherical foliation can have spatial maxima and minima, but no origins. The mass and radius functions may be one increasing and one decreasing without causing shell crossings. This case most naturally describes a snakelike, variable density void in a more gently varying inhomogeneous background, although regions that develop an overdensity are also possible. The Szekeres models with plane foliation can have neither spatial extrema nor origins, cannot be spatially flat, and they cannot have more inhomogeneity than the corresponding Ellis model, but a planar surface can be the boundary between regions of spherical and pseudospherical foliation.

Free streaming in a mixture of collisionless nonrelativistic dark matter (DM) particles is studied by solving the linearized Vlasov equation implementing methods from the theory of multicomponent plasmas. The mixture includes fermionic, condensed and noncondensed bosonic particles decoupling in equilibrium while relativistic, heavy thermal relics that decoupled when nonrelativistic [weakly interacting massive particles (WIMPs)], and sterile neutrinos that decouple out of equilibrium when they are relativistic. The different components interact via the self-consistent gravitational potential that they source. The free-streaming length ${\lambda }_{fs}$ is obtained from the marginal zero of the gravitational polarization function, which separates short wavelength Landau-damped from long-wavelength Jeans-unstable collective modes. At redshift $z$ I find $\frac{1}{{\lambda }_{fs}^2(z)}=\frac{1}{(1+z)}[\frac{0.071}{\mathrm{kpc}}{]}^2\sum _a{\nu }_a{g}_{d,a}^{2/3}(m_a/\mathrm{keV}{)}^2{I}_a$, where $0\le {\nu }_a\le 1$ are the fractions of the respective DM components of mass $m_a$ that decouple when the effective number of ultrarelativistic degrees of freedom is $g_{d,a}$, and $I_a$ are dimensionless ratios of integrals of the distribution functions which only depend on the microphysics at decoupling and are obtained explicitly in all the cases considered. If sterile neutrinos produced either resonantly or nonresonantly that decouple near the QCD scale are the only DM component, I find ${\lambda }_{fs}(0)\simeq 7\mathrm{kpc}(\mathrm{keV}/m)$ (nonresonant), ${\lambda }_{fs}(0)\simeq 1.73\mathrm{kpc}(\mathrm{keV}/m)$ (resonant). If WIMPs with $m_{\mathrm{wimp}}\gtrsim 100\mathrm{GeV}$ decoupling at $T_d\gtrsim 10\mathrm{MeV}$ are present in the mixture with ${\nu }_{\mathrm{wimp}}\gg {10}^{-12}$, ${\lambda }_{fs}(0)\lesssim 6.5\times {10}^{-3}\mathrm{pc}$ is dominated by cold dark matter (CDM). If a Bose-Einstein condensate is a DM component its free-streaming length is consistent with CDM because of the infrared enhancement of the distribution function.

We compare the infrared Dirac-Born-Infeld brane inflation model to observations using a Bayesian analysis. The current data cannot distinguish it from the $\Lambda \mathrm{CDM}$ model but is able to give interesting constraints on various microscopic parameters including the mass of the brane moduli potential, the fundamental string scale, the charge or warp factor of throats, and the number of the mobile branes. We quantify some distinctive testable predictions with stringy signatures, such as the large non-Gaussianity, and the large, but regional, running of the spectral index. These results illustrate how we may be able to probe aspects of string theory using cosmological observations.

The three-flavor crystalline color-superconducting (CCS) phase of quantum chromodynamics (QCD) is a candidate phase for the ground state of cold matter at moderate densities above the density of the deconfinement phase transition. Apart from being a superfluid, the CCS phase has properties of a solid, such as a lattice structure and a shear modulus, and hence the ability to sustain multipolar deformations in gravitational equilibrium. We construct equilibrium configurations of hybrid stars composed of nuclear matter at low, and CCS quark matter at high, densities. Phase equilibrium between these phases is possible only for rather stiff equations of state of nuclear matter and large couplings in the effective Nambu—Jona-Lasinio Lagrangian describing the CCS state. We identify a new branch of stable CCS hybrid stars within a broad range of central densities which, depending on the details of the equations of state, either bifurcate from the nuclear sequence of stars when the central density exceeds that of the deconfinement phase transition or form a new family of configurations separated from the purely nuclear sequence by an instability region. The maximum masses of our nonrotating hybrid configurations are consistent with the presently available astronomical bounds. The sequences of hybrid configurations that rotate near the mass-shedding limit are found to be more compact and thus support substantially larger spins than their same mass nuclear counterparts.

We continue to explore the consequences of the recently discovered Minkowski space structure of the Higgs potential in the two-Higgs-doublet model. Here, we focus on the vacuum properties. The search for extrema of the Higgs potential is reformulated in terms of 3-quadrics in the $3+1$-dimensional Minkowski space. We prove that 2HDM cannot have more than two local minima in the orbit space and that a twice-degenerate minimum can arise only via spontaneous violation of a discrete symmetry of the Higgs potential. Investigating topology of the 3-quadrics, we give concise criteria for existence of noncontractible paths in the Higgs orbit space. We also study explicit symmetries of the Higgs potential/Lagrangian and their spontaneous violation from a wider perspective than usual.

We calculate the critical value of the hopping parameter, ${\kappa }_c$, in lattice QCD, up to two loops in perturbation theory. We employ the Sheikholeslami-Wohlert (clover) improved action for fermions and the Symanzik improved gluon action with 4- and 6-link loops. The quantity which we study is a typical case of a vacuum expectation value resulting in an additive renormalization; as such, it is characterized by a power (linear) divergence in the lattice spacing, and its calculation lies at the limits of applicability of perturbation theory. Our results are polynomial in $c_{\mathrm{SW}}$ (clover parameter) and cover a wide range of values for the Symanzik coefficients $c_i$. The dependence on the number of colors $N$ and the number of fermion flavors $N_f$ is shown explicitly. In order to compare our results to nonperturbative evaluations of ${\kappa }_c$ coming from Monte Carlo simulations, we employ an improved perturbation theory method for improved actions.