Current cosmological constraints from cosmic microwave background anisotropies are typically derived assuming a standard recombination scheme, however additional resonance and ionizing radiation sources can delay recombination, altering the cosmic ionization history and the cosmological inferences drawn from the cosmic microwave background data. We show that for recent observations of the cosmic microwave background anisotropy, from the Wilkinson microwave anisotropy probe satellite mission (WMAP) 5-year survey and from the arcminute cosmology bolometer array receiver experiment, additional resonance radiation is nearly degenerate with variations in the spectral index, $n_s$, and has a marked effect on uncertainties in constraints on the Hubble constant, age of the universe, curvature and the upper bound on the neutrino mass. When a modified recombination scheme is considered, the redshift of recombination is constrained to $z_{*}=1078\pm 11$, with uncertainties in the measurement weaker by 1 order of magnitude than those obtained under the assumption of standard recombination while constraints on the shift parameter are shifted by $1\sigma$ to $\mathcal{R}=1.734\pm 0.028$. From the WMAP5 data we obtain the following constraints on the resonance and ionization sources parameters: ${ϵ}_{\alpha }<0.39$ and ${ϵ}_i<0.058$ at 95% c.l.. Although delayed recombination limits the precision of parameter estimation from the WMAP satellite, we demonstrate that this should not be the case for future, smaller angular scales measurements, such as those by the Planck satellite mission.

Several accurate analyses have revealed a statistically significant north-south ecliptic asymmetry in the large-angle correlations strength of the cosmic microwave background (CMB) radiation temperature field data from the Wilkinson Microwave Anisotropy Probe (WMAP). This asymmetry is inconsistent with the statistical isotropy expected in the concordance cosmological model $\Lambda \mathrm{CDM}$. It has been suggested that a possible cause-effect relationship exists between this large-angle anisotropy and the anomalous CMB quadrupole-octopole planes alignment. In turn, this later phenomenon (or both) would be a consequence of one or more of the following undesired effects in CMB data: a systematic error in the data processing or in the instrument characterization, residual foregrounds, and large-angle correlations induced by the incomplete sky CMB data (cut-sky masks are needed to reject galactic foregrounds). Here, it is proved that the north-south asymmetry is unrelated to the quadrupole ($\ell =2$) and the octopole ($\ell =3$) properties because we find, at high confidence levels, such large-angle anisotropy in three- and five-year WMAP CMB maps containing only the multipole components $4\le \ell \le 10$. The statistical significance depends on both, the CMB map analyzed as well as the cut-sky mask applied to exclude foregrounds. In general, we obtain that the significance level of the north-south asymmetry is less in five-year WMAP data with KQ75 ($\gtrsim 90\%\mathrm{CL}$) than it is in three-year data with Kp0 ($\gtrsim 96\%\mathrm{CL}$). For instance, in the WMAP internal linear combination (ILC)-five-year map with the KQ75 mask (a sky cut of 28.4%) this phenomenon is observed at 92.7% CL, whereas for the WMAP ILC-three-year map with the Kp0 mask (a sky cut of 23.5%) this phenomenon appears at 96.5% CL. Moreover, it is also shown that this hemispherical asymmetry is unlikely due to systematics or foreground contaminants, because it is present in single-frequency, multifrequency, and cleaned ILC-type CMB maps. Additionally, robustness tests show that the statistical significance of the north-south asymmetry is affected by the use of the KQ85 and KQ75 masks in five-year single-frequency WMAP CMB maps, whereas it is insensitive with respect to application of the Kp2 and Kp0 masks in three-year single-frequency WMAP CMB maps. The confidence levels were obtained using sets of Monte Carlo CMB maps produced according to the $\Lambda \mathrm{CDM}$ model.

Motivated by the eXciting dark matter model of Finkbeiner and Weiner, hypothesized to explain the 511 keV signal in the center of the Milky Way, we consider the cosmic microwave background and 21-cm signatures of models of dark matter with collisional long-lived excited states. We compute the relic excitation fraction from the early Universe for a variety of assumptions about the collisional de-excitation cross section and thermal decoupling. The relic excitation fraction can be as high as 1% for natural regions of parameter space, but could be orders of magnitude smaller. Since the lifetime of the excited state is naturally greater than ${10}^{13}\mathrm{s}$, we discuss the signatures of such relic excitation on cosmic microwave background and high-$z$ 21-cm observations. Such models have potentially richer astrophysical signals than the traditional weakly interacting massive particle annihilations and decays, and may have observable consequences for future generations of experiments.

We describe an approximate statistical model for the sample variance distribution of the nonlinear matter power spectrum that can be calibrated from limited numbers of simulations. Our model retains the common assumption of a multivariate normal distribution for the power spectrum band powers but takes full account of the (parameter-dependent) power spectrum covariance. The model is calibrated using an extension of the framework in Habib et al. (2007) to train Gaussian processes for the power spectrum mean and covariance given a set of simulation runs over a hypercube in parameter space. We demonstrate the performance of this machinery by estimating the parameters of a power-law model for the power spectrum. Within this framework, our calibrated sample variance distribution is robust to errors in the estimated covariance and shows rapid convergence of the posterior parameter constraints with the number of training simulations.

In the large extra dimensional Kaluza-Klein (KK) scenario, where the usual standard model (SM) matter is confined to a $3+1$-dimensional hypersurface called the 3-brane and gravity can propagate to the bulk ($D=4+d$, $d$ being the number of extra spatial dimensions), the light graviton KK modes can be produced inside the supernova core due to the usual nucleon-nucleon bremstrahlung, electron-positron, and photon-photon annihilations. This photon inside the supernova becomes a plasmon due to the plasma effect. In this paper, we study the energy-loss rate of SN 1987A due to the KK gravitons produced from the plasmon-plasmon annihilation. We find that the SN 1987A cooling rate leads to the conservative bound $M_D>22.9\mathrm{TeV}$ and 1.38 TeV for the case of two and three spacelike extra dimensions.

Coherent oscillations of a scalar field can mimic the behavior of a perfect fluid with an equation-of-state parameter determined by the properties of the potential, possibly driving accelerated expansion in the early Universe (inflation) and/or in the Universe today (dark energy) or behaving as dark matter. We consider the growth of inhomogeneities in such a field, mapping the problem to that of two coupled anharmonic oscillators. We provide a simple physical argument that oscillating fields with a negative equation-of-state parameter possess a large-scale dynamical instability to growth of inhomogeneities. This instability renders these models unsuitable for explaining cosmic acceleration. We then consider the gravitational instability of oscillating fields in potentials that are close to, but not precisely, harmonic. We use these results to show that if axions make up the dark matter, then the small-scale cutoff in the matter power spectrum is around ${10}^{-15}{M}_{\oplus }$.

We explore the relevance of confinement in quark matter models for the possible quark core of neutron stars. For the quark phase, we adopt the equation of state derived with the field correlator method, extended to the zero temperature limit. For the hadronic phase, we use the microscopic Brueckner-Hartree- Fock many-body theory. We find that the currently adopted value of the gluon condensate $G_2\simeq 0.006–0.007{\mathrm{GeV}}^4$, which gives a critical temperature $T_c\simeq 170\mathrm{MeV}$, produces maximum masses which are only marginally consistent with the observational limit, while larger masses are possible if the gluon condensate is increased.

We developed algorithms which allow us to find regimes of the signal-recycled Fabry-Perot–Michelson interferometer [for example, the Advanced Laser Interferometric Gravitational Wave Observatory (LIGO)], optimized concurrently for two (binary inspirals $+$ bursts) and three (binary inspirals $+$ bursts $+$ millisecond pulsars) types of gravitational wave sources. We show that there exists a relatively large area in the interferometer parameters space where the detector sensitivity to the first two kinds of sources differs only by a few percent from the maximal ones for each kind of source. In particular, there exists a specific regime where this difference is $\approx 0.5\%$ for both of them. Furthermore, we show that even more multipurpose regimes are also possible that provide significant sensitivity gain for millisecond pulsars with only minor sensitivity degradation for binary inspirals and bursts.

In many extensions of the standard model, the Higgs sector often contains an additional pseudoscalar boson. A good example is the SU(3) simplest little Higgs model, which accommodates a light pseudoscalar boson $\eta$ with quite different characteristics from those in other multi-Higgs-doublet models. We study various phenomenological signatures of the $\eta$ at the CERN LHC. In particular, we calculate in details both production and decays in the Drell-Yan type channel $q\overline{q}\to Z/Z^{\prime }\to h\eta$, and in the associated production with a $t\overline{t}$ pair, $gg(q\overline{q})\to t\overline{t}\eta$. We emphasize the ${\tau }^{+}{\tau }^{-}$ decay mode of the $\eta$ boson when its mass is below the $b\overline{b}$ threshold. We show that $t\overline{t}\eta$ production is in fact large enough to give a sizable number of events while suppressing the backgrounds. We also comment on the direct gluon fusion process and the indirect decay from the heavy $T$ quark ($T\to t\eta$).

We evaluate the Casimir force between two parallel plates in Randall-Sundrum (RS) scenarios extended by $q$ compact dimensions. After giving exact expressions for one extra compact dimension (6D RS model), we generalize to an arbitrary number of compact dimensions. We present the complete calculation for both the two-brane scenario (RSI model) and the one-brane scenario (RSII model) using the method of summing over the modes. We investigate the effects of extra dimensions on the magnitude and sign of the force, and comment on limits for the size and number of the extra dimensions.

Dynamical breaking of supersymmetry was long thought to be an exceptional phenomenon, but recent developments have altered this view. A question of great interest in the current framework is the value of the underlying scale of supersymmetry breaking. The “little hierarchy” problem suggests that supersymmetry should be broken at low energies. Within one class of models, low energy breaking can be achieved as a consequence of symmetries, without requiring odd coincidences. The low energy theories are distinguished by the presence or absence of $R$ symmetries; in either case, and especially the latter, one often finds modifications of the minimal gauge-mediated spectrum which can further ameliorate problems of fine-tuning. Various natural mechanisms exist to solve the $\mu$ problem in this framework.

We discuss the collider phenomenology of TeV $Z^{\prime }$ gauge bosons related to the absence of a bare $\mu$-term in the superpotential. Decays of the type $Z^{\prime }\to \mathrm{\text{Higgsinos}}$ can directly test whether a gauge symmetry is responsible for forbidding the Higgsino mass. Decays to multilepton final states may allow these signatures to be observed at the CERN Large Hadron Collider. We comment on whether it will be possible to state definitively that the $\mu$-term is forbidden via a gauge symmetry.

We present a new framework for calculating multijet observables through resummation. The framework is based on the factorization of scattering amplitudes in an asymptotic limit. By imposing simple constraints on the analytic behavior of the result when applied away from this limit, we get good agreement with the known lowest order perturbative behavior of the scattering amplitude, and predictions for the behavior to all orders in the perturbative series. As an example of application we study predictions for Higgs boson production through gluon fusion at the LHC in association with at least two jets.

We study electric dipole moments of electrons and protons in $E(6)$-inspired supersymmetric models with an extra $U(1)$ invariance. Compared to the Minimal Supersymmetric Standard Model, in addition to offering a natural solution to the $\mu$ problem and predicting a larger mass for the lightest Higgs boson, these models are found to yield suppressed electric dipole moments.

We propose a new solution to the supersymmetric flavor problem without flavor-blind mediation. Our proposal is to enforce a continuous or a suitably large discrete $R$-symmetry on weak scale supersymmetry, so that Majorana gaugino masses, trilinear $A$ terms, and the $\mu$ term are forbidden. We find that replacing the minimal supersymmetric standard model with an $R$-symmetric supersymmetric model allows order one flavor-violating soft masses, even for squarks of order a few hundred GeV. The minimal $R$-symmetric supersymmetric model contains Dirac gaugino masses and $R$-symmetric Higgsino masses with no left-right mixing in the squark or slepton sector. Dirac gaugino masses of order a few TeV with vanishing $A$ terms solve most flavor problems, while the $R$-symmetric Higgs sector becomes important at large $\tan \beta$. ${ϵ}_K$ can be accommodated if $CP$ is preserved in the SUSY breaking sector, or if there is a moderate flavor degeneracy, which can arise naturally. ${ϵ}^{\prime }/ϵ$, as well as neutron and electron electric dipole moments, are easily within experimental bounds. The most striking phenomenological distinction of this model is the order one flavor violation in the squark and slepton sector, while the Dirac gaugino masses tend to be significantly heavier than the corresponding squark and slepton masses.

We have calculated the radiative corrections to the Dalitz plot of baryon semileptonic decays with angular correlation between polarized emitted baryons and charged leptons. This work covers both charged and neutral decaying baryons and is restricted to the so-called three-body region of the Dalitz plot. Also it is specialized at the center-of-mass frame of the emitted baryon. We have considered terms up to order $(\alpha /\pi )(q/M_1{)}^0$, where $q$ is the momentum transfer and $M_1$ is the mass of the decaying baryon, and neglected terms of order $(\alpha /\pi )(q/M_1{)}^n$ for $n\ge 1$. The expressions displayed are ready to obtain numerical results, suitable for model-independent experimental analyses.

We study the tetraquark states with $I^G{J}^{PC}=1^{-}{1}^{-+}$ in the QCD sum rule. After exhausting all possible flavor structures, we analyze both the Shifman-Vainshtein-Zakharov (SVZ) and finite energy sum rules. Both approaches lead to a mass around 1.6 GeV for the state with the quark contents $qq\overline{q}\overline{q}$, and around 2.0 GeV for the state with the quark contents $qs\overline{q}\overline{s}$. The flavor structure $(\overline{\mathbf{3}}\otimes \overline{\mathbf{6}})\oplus (\mathbf{6}\otimes \mathbf{3})$ is preferred. Our analysis strongly indicates that both ${\pi }_1(1600)$ and ${\pi }_1(2015)$ are also compatible with the exotic tetraquark interpretation, which are sometimes labeled as candidates of the $1^{-+}$ hybrid mesons. Moreover one of their dominant decay modes is a pair of axial-vector and pseudoscalar mesons such as $b_1(1235)\pi$, which is sometimes considered as the characteristic decay mode of the hybrid mesons.

We obtain the relaxation time for the shear viscous stress for various geometries using the “membrane paradigm” formula proposed recently. We consider the generic Schwarzschild–anti-de Sitter black holes (SAdS), the generic $\mathrm{D}p$-brane, the Klebanov-Tseytlin (KT) geometry, and the $\mathcal{N}=2^{*}$ theory. The formula is the “shear mode” result and is not fully trustable, but it may be helpful to learn some generic behaviors about the relaxation time. For example, a simple formula summarizes all known results for SAdS, and a single expression summarizes the results for the $\mathrm{D}p$-brane and the KT geometry.