A long-range intergalactic force between dark matter (DM) particles, mediated by an ultralight scalar, is tightly constrained by galactic dynamics and large scale structure formation. We examine the implications of such a ‘‘dark force” for several terrestrial experiments, including Eötvös tests of the Weak Equivalence Principle (WEP), direct-detection DM searches, and collider studies. The presence of a dark force implies a nonvanishing effect in Eötvös tests that could be probed by current and future experiments depending on the DM model. For scalar DM that is a singlet under the standard model gauge groups, a dark force of astrophysically relevant magnitude is ruled out in large regions of parameter space by the DM relic density and WEP constraints. WEP tests also imply constraints on the Higgs-exchange contributions to the spin-independent (SI) DM-nucleus direct-detection cross section. For WIMP scenarios, these considerations constrain Higgs-exchange contributions to the SI cross section to be subleading compared to gauge-boson mediated contributions. In multicomponent DM scenarios, a dark force would preclude large shifts in the rate for Higgs decay to two photons associated with DM-multiplet loops that might otherwise lead to measurable deviations at the LHC or a future linear collider. The combination of observations from galactic dynamics, large scale structure formation, Eötvös experiments, DM-direct-detection experiments, and colliders can further constrain the size of new long-range forces in the dark sector.

We report a search for the decay $\psi (2S)\to \gamma {\eta }_c(2S)$ in a sample of $25.9\times {10}^6$ $\psi (2S)$ events collected with the CLEO-c detector. No signals are observed in any of the 11 exclusive ${\eta }_c(2S)$ decay modes studied, or in their sum. Product branching fraction upper limits are determined as a function of $\Gamma [{\eta }_c(2S)]$ for the 11 individual modes.

The ultraviolet/infrared (UV/IR) mixing of noncommutative field theories has been recently shown to be a generic feature of translation-invariant associative products. In this paper we propose to take into account the quantum corrections of the model to modify in this way the noncommutative action. This idea was already used to cure the UV/IR mixing for theories on Moyal space. We show that in the present framework also, this proposal proves successful for curing the mixing. We achieve this task by explicit calculations of one and higher loops Feynman amplitudes. For the sake of completeness, we compute the form of the new action in the matrix base for the Wick-Voros product.

Despite suggestions to the contrary, we show in this paper that the usual dispersive form of the electromagnetic energy density must be used to derive the Lifshitz force between parallel dielectric media. This conclusion follows from the general form of the quantum vacuum energy, which is the basis of the multiple-scattering formalism. As an illustration, we explicitly derive the Lifshitz formula for the interaction between parallel dielectric semispaces, including dispersion, starting from the expression for the total energy of the system. The issues of constancy of the energy between parallel plates and of the observability of electrostrictive forces are briefly addressed.

In previous work, starting from the Moyal plane, we formulated interacting theories of matter and gauge fields with only the former fields twisted. In this approach, gauge theories, including the standard model, can be formulated without new gauge degrees of freedom. We show their underlying symmetry algebra to be Poincaré quasi-Hopf. The associated spacetime algebra is hence nonassociative.

We investigate static, spherically symmetric solutions of an Einstein-Yang-Mills-Chern-Simons system with negative cosmological constant, for an $SO(6)$ gauge group. For a particular value of the Chern-Simons coefficient, this model can be viewed as a truncation of the five-dimensional maximal gauged supergravity and we expect that the basic properties of the solutions in the full model to persist in this truncation. Both globally regular, particlelike solutions and black holes are considered. In contrast with the Abelian case, the contribution of the Chern-Simons term is nontrivial already in the static, spherically symmetric limit. We find two types of solutions: the generic configurations whose magnetic gauge field does not vanish fast enough at infinity (although the spacetime is asymptotically AdS), whose mass function is divergent, and the special configurations, whose existence depends on the Chern–Simons term, which are endowed with finite mass. In the case of the generic configurations, we argue that the divergent mass implies a nonvanishing trace for the stress tensor of the dual $d=4$ theory.

The problem of a compact binary system whose components move on circular orbits is addressed using two different approximation techniques in general relativity. The post-Newtonian (PN) approximation involves an expansion in powers of $v/c\ll 1$, and is most appropriate for small orbital velocities $v$. The perturbative self-force analysis requires an extreme mass ratio $m_1/m_2\ll 1$ for the components of the binary. A particular coordinate-invariant observable is determined as a function of the orbital frequency of the system using these two different approximations. The post-Newtonian calculation is pushed up to the third post-Newtonian (3PN) order. It involves the metric generated by two point particles and evaluated at the location of one of the particles. We regularize the divergent self-field of the particle by means of dimensional regularization. We show that the poles $\propto (d-3{)}^{-1}$ appearing in dimensional regularization at the 3PN order cancel out from the final gauge invariant observable. The 3PN analytical result, through first order in the mass ratio, and the numerical self-force calculation are found to agree well. The consistency of this cross cultural comparison confirms the soundness of both approximations in describing compact binary systems. In particular, it provides an independent test of the very different regularization procedures invoked in the two approximation schemes.

We investigate the impact of the tau and bottom Yukawa couplings on the transport dynamics for electroweak baryogenesis in supersymmetric extensions of the standard model. Although it has generally been assumed in the literature that all Yukawa interactions except those involving the top quark are negligible, we find that the tau and bottom Yukawa interaction rates are too fast to be neglected. We identify an illustrative “lepton-mediated electroweak baryogenesis” scenario in which the baryon asymmetry is induced mainly through the presence of a left-handed leptonic charge. We derive analytic formulas for the computation of the baryon asymmetry that, in light of these effects, are qualitatively different from those in the established literature. In this scenario, for fixed $CP$-violating phases, the baryon asymmetry has opposite sign compared to that calculated using established formulas.

We provide an analytical expression for the trispectrum of the cosmic microwave background (CMB) temperature anisotropies induced by cosmic strings. Our result is derived for the small angular scales under the assumption that the temperature anisotropy is induced by the Gott-Kaiser-Stebbins effect. The trispectrum is predicted to decay with a noninteger power-law exponent ${\ell }^{-\rho }$ with $6<\rho <7$, depending on the string microstructure, and thus on the string model. For Nambu-Goto strings, this exponent is related to the string mean square velocity and the loop distribution function. We then explore two classes of wave number configuration in Fourier space, the kite and trapezium quadrilaterals. The trispectrum can be of any sign and appears to be strongly enhanced for all squeezed quadrilaterals.

We perform a detailed phenomenological analysis of how well hadronization in nuclear environments can be described in terms of effective fragmentation functions. The medium modified fragmentation functions are assumed to factorize from the partonic scattering cross sections and evolve in the hard scale in the same way as the standard or vacuum fragmentation functions. Based on precise data on semi-inclusive deep-inelastic scattering off nuclei and hadron production in deuteron-gold collisions, we extract sets of effective fragmentation functions for pions and kaons at next-to-leading order accuracy. The obtained sets provide a rather accurate description of the kinematical dependence of the analyzed cross sections and are found to differ significantly from standard fragmentation functions both in shape and magnitude. Our results support the notion of factorization and universality in the studied nuclear environments, at least in an effective way and within the precision of the available data.

The differential energy distribution for electrons and taus produced from lepton pair production from muons in transit through materials is numerically evaluated. We use the differential cross section to calculate underground lepton fluxes from an incident atmospheric muon flux, considering contributions from both conventional and prompt fluxes. An approximate form for the charged current differential neutrino cross section is provided and used to calculate single lepton production from atmospheric neutrinos. We compare the fluxes of underground leptons produced from incident muons with those produced from incident neutrinos and photons from muon bremsstrahlung. We discuss their relevance for underground detectors.

We investigate shock wave effects upon the diffuse supernova neutrino background using dynamic profiles taken from hydrodynamical simulations and calculating the neutrino evolution in three flavors with the $S$-matrix formalism. We show that the shock wave impact is significant and introduces modifications of the relic fluxes by about 20% and of the associated event rates at the level of 10%–20%. Such an effect is important since it is of the same order as the rate variation introduced when different oscillation scenarios (i.e., hierarchy or ${\theta }_{13}$) are considered. In addition, due to the shock wave, the rates become less sensitive to collective effects, in the inverted hierarchy and when ${sin}^{2}2{\theta }_{13}$ is between the Chooz limit and ${10}^{-5}$. We propose a simplified model to account for shock wave effects in future predictions.

Using the published KTeV samples of $K_L\to {\pi }^{\pm }{e}^{\mp }\nu$ and $K_L\to {\pi }^{\pm }{\mu }^{\mp }\nu$ decays, we perform a reanalysis of the scalar and vector form factors based on the dispersive parametrization. We obtain phase-space integrals $I_K^e=0.15446\pm 0.00025$ and $I_K^{\mu }=0.10219\pm 0.00025$. For the scalar form factor parametrization, the only free parameter is the normalized form factor value at the Callan-Treiman point ($C$); our best-fit results in $\ln C=0.1915\pm 0.0122$. We also study the sensitivity of $C$ to different parametrizations of the vector form factor. The results for the phase-space integrals and $C$ are then used to make tests of the standard model. Finally, we compare our results with lattice QCD calculations of $F_K/F_{\pi }$ and $f_{+}(0)$.

The metric $f(R)$ theories of gravity are generalized to five-dimensional spacetimes. By assuming a hypersurface-orthogonal Killing vector field representing the compact fifth dimension, the five-dimensional theories are reduced to their four-dimensional formalism. Then we study the cosmology of a special class of $f(R)=\alpha R^m$ models in a spatially flat Friedmann-Robertson-Walker spacetime. It is shown that the parameter $m$ can be constrained to a certain range by the current observed deceleration parameter, and its lower bound corresponds to the Kaluza-Klein theory. It turns out that both expansion and contraction of the extra dimension may prescribe the smooth transition from the deceleration era to the acceleration era in the recent past as well as an accelerated scenario for the present Universe. Hence, five-dimensional $f(R)$ gravity can naturally account for the present accelerated expansion of the Universe. Moreover, the models predict a transition from acceleration to deceleration in the future, followed by a cosmic recollapse within finite time. This differs from the prediction of the five-dimensional Brans-Dicke theory but is inconsistent with a recent prediction based on loop quantum cosmology.

The dynamical consistency of the nonprojectable version of Hořava gravity is investigated by focusing on the asymptotically flat case. It is argued that for generic solutions of the constraint equations the lapse must vanish asymptotically. We then consider particular values of the coupling constants for which the equations are tractable and in that case we prove that the lapse must vanish everywhere—and not only at infinity. Put differently, the Hamiltonian constraints are generically all second-class. We then argue that the same feature holds for generic values of the couplings, thus revealing a physical inconsistency of the theory. In order to cure this pathology, one might want to introduce further constraints but the resulting theory would then lose much of the appeal of the original proposal by Hořava. We also show that there is no contradiction with the time-reparametrization invariance of the action, as this invariance is shown to be a so-called “trivial gauge symmetry” in Hořava gravity, hence with no associated first-class constraints.

We consider a noncritical holographic model constructed from an intersecting brane configuration $\mathrm{D}4/\overline{\mathrm{D}4}\mathrm{\text{−}}\mathrm{D}4$ with an external magnetic field. We investigate the influences of this magnetic field on strongly coupled dynamics by the gauge/gravity correspondence.

A novel formalism for the evaluation of the Casimir-Polder potential in an arbitrary gauge of vector potentials is introduced. The ground state energy of a neutral atom in the presence of an infinite two-dimensional plane with Chern-Simons interaction is derived at zero temperature. The essential feature of the result is its dependence on the antisymmetric part of a dipole moment correlation function.

We propose a scenario in which the Planck scale is dynamically linked to the electroweak scale induced by top condensation. The standard model field content, without the Higgs, is promoted to a 5D warped background. There is also an additional 5D fermion with the quantum numbers of the right-handed top. Localization of the zero-modes leads, at low-energies, to a Nambu-Jona-Lasinio model that also stabilizes the radion field dynamically thus explaining the hierarchy between the Planck scale and $v_{\mathrm{EW}}=174\mathrm{GeV}$. The top mass arises dynamically from the electroweak breaking condensate. The other standard model fermion masses arise naturally from higher-dimension operators, and the fermion mass hierarchies and flavor structure can be explained from the localization of the zero-modes in the extra dimension. If other contributions to the radion potential except those directly related to electroweak symmetry breaking are engineered to be suppressed, the KK scale is predicted to be about 2 orders of magnitude above the electroweak scale, rendering the model easily consistent with electroweak precision data. The model predicts a heavy (composite) Higgs with a mass of about 500 GeV and standard-model-like properties, and a vectorlike quark with non-negligible mixing with the top quark and mass in the 1.6–2.9 TeV range. Both can be within the reach of the LHC. It also predicts a radion with a mass of a few GeV that is very weakly coupled to standard model matter.

We consider black $p$-brane solutions of the low-energy string action, computing scalar perturbations. Using standard methods, we derive the wave equations obeyed by the perturbations and treat them analytically and numerically. We have found that tensorial perturbations obtained via a gauge-invariant formalism leads to the same results as scalar perturbations. No instability has been found. Asymptotically, these solutions typically reduce to a ${\mathrm{AdS}}_{(p+2)}\times S^{(8-p)}$ space which, in the framework of Maldacena’s conjecture, can be regarded as a gravitational dual to a conformal field theory defined in a ($p+1$)-dimensional flat space-time. The results presented open the possibility of a better understanding the AdS/CFT correspondence, as originally formulated in terms of the relation among brane structures and gauge theories.

We propose a new scenario for the early Universe where there is a smooth transition between an early de Sitter-like phase and a radiation-dominated era. In this model, the matter content is modeled by a new type of generalized Chaplygin gas [6] for the early Universe, with an underlying scalar field description. We study the gravitational waves generated by the quantum fluctuations. In particular, we calculate the gravitational-wave power spectrum, as it would be measured today, following the method of the Bogoliubov coefficients. We show that the high frequencies region of the spectrum depends strongly on one of the parameters of the model. On the other hand, we use the number of $e$ folds, along with the power spectra and spectral index of the scalar perturbations, to constrain the model observationally.