Generalized Einstein-Aether vector field models have been shown to provide, in the weak field regime, modifications to gravity which can be reconciled with the successful modified Newtonian dynamics (MOND) proposal. Very little is known, however, on the function $\mathcal{F}(\mathcal{K})$ defining the vector field Lagrangian so that an analysis of the viability of such theories at the cosmological scales has never been performed. As a first step along this route, we rely on the relation between $\mathcal{F}(\mathcal{K})$ and the MOND interpolating function $\mu (a/a_0)$ to assign the vector field Lagrangian thus obtaining what we refer to as MONDian vector models. Since they are able by construction to recover the MOND successes on galaxy scales, we investigate whether they can also drive the observed accelerated expansion by fitting the models to the type Ia supernovae data. Should this be the case, we have a unified framework where both dark energy and dark matter can be seen as different manifestations of a single vector field. It turns out that both MONDian vector models are able to well fit the low redshift data on type Ia supernovae, while some tension could be present in the high $z$ regime.

We use quadratic maximum-likelihood (QML) estimators to constrain models with Gaussian but statistically anisotropic CMB fluctuations, using CMB maps with realistic sky-coverage and instrumental noise. This approach is optimal when the anisotropy is small, or when checking for consistency with isotropy. We demonstrate the power of the QML approach by applying it to the WMAP data to constrain several models which modulate the observed CMB fluctuations to produce a statistically anisotropic sky. We first constrain an empirically motivated spatial modulation of the observed CMB fluctuations, reproducing marginal evidence for a dipolar modulation pattern with amplitude 7% at $l\lesssim 60$, but demonstrate that the effect decreases at higher multipoles and is $\lesssim 1\%$ at $l\sim 500$. We also look for evidence of a direction-dependent primordial power spectrum, finding a very statistically significant quadrupole signal nearly aligned with the ecliptic plane; however we argue this anisotropy is largely contaminated by observational systematics. Finally, we constrain the anisotropy due to a spatial modulation of adiabatic and isocurvature primordial perturbations, and discuss the close relationship between anisotropy and non-Gaussianity estimators.

We show that the anomaly of the positron fraction observed by the PAMELA experiment can be attributed to recent supernova explosion(s) in a dense gas cloud near the Earth. Protons are accelerated around the supernova remnant. Electrons and positrons are created through hadronic interactions inside the dense gas cloud. Their spectrum is harder than that of the background because the supernova remnant spends much time in a radiative phase. Our scenario predicts that the antiproton flux dominates that of the background for $\gtrsim 100\mathrm{GeV}$. We compare the results with observations (Fermi, HESS, PPB-BETS, and ATIC).

We use QCD sum rules to test the nature of the meson $X(3872)$, assumed to be a mixture between charmonium and exotic molecular $[c\overline{q}][q\overline{c}]$ states with $J^{\mathrm{PC}}=1^{++}$. We find that there is only a small range for the values of the mixing angle $\theta$ that can provide simultaneously good agreement with the experimental value of the mass and the decay width, and this range is $5^0\le \theta \le {13}^0$. In this range we get $m_X=(3.77\pm 0.18)\mathrm{GeV}$ and $\Gamma (X\to J/\psi {\pi }^{+}{\pi }^{-})=(9.3\pm 6.9)\mathrm{MeV}$, which are compatible, within the errors, with the experimental values. We, therefore, conclude that the $X(3872)$ is approximately 97% a charmonium state with 3% admixture of $\sim 88\%$ $D^0{D}^{*0}$ molecule and $\sim 12\%$ $D^{+}{D}^{*-}$ molecule.

We study the potential of the LHC and future low-energy experiments to precisely measure the underlying model parameters of a new $Z^{\prime }$ boson. We emphasize the complementary information obtained from both on- and off-peak LHC dilepton data, from the future $Q$-weak measurement of the weak charge of the proton, and from a proposed measurement of parity violation in low-energy Møller scattering. We demonstrate the importance of off-peak LHC data and $Q$-weak for removing sign degeneracies between $Z^{\prime }$ couplings that occur if only on-peak LHC data is studied. A future precision measurement of low-energy Møller scattering can resolve a scaling degeneracy between quark and lepton couplings that remains after analyzing LHC dilepton data, permitting an extraction of the individual $Z^{\prime }$ couplings rather than combinations of them. We study how precisely $Z^{\prime }$ properties can be extracted for LHC integrated luminosities ranging from a few inverse femtobarns to super-LHC values of an inverse attobarn. For the several example cases studied with $M_{Z^{\prime }}=1.5\mathrm{TeV}$, we find that coupling combinations can be determined with relative uncertainties reaching $\pm 30\%$ with $30{\mathrm{fb}}^{-1}$ of integrated luminosity, while $\pm 50\%$ is possible with $10{\mathrm{fb}}^{-1}$. With SLHC luminosities of $1{\mathrm{ab}}^{-1}$, we find that products of quark and lepton couplings can be probed to $\pm 10\%$.

We study flavor-violating processes in the production or decay of a neutral pseudoscalar meson $P^0$ in the framework of a type-III two Higgs doublet model with four-texture Yukawa couplings. We use a version of the model where Yukawa interactions of neutral Higgs bosons allow for flavor change at the tree-level, but conserve $CP$ symmetry. The physical Yukawa couplings respect $CP$-invariance due to the Hermiticity conditions that we impose on the fermion mass matrices. We focus on all possible ${\tau }^{\pm }\to l^{\pm }{P}^0$ and $P^0\to l^{+}{l}^{\prime -}$ decay channels, where $l$, $l^{\prime }$ are charged leptons. We find that these processes provide complementary information on quark and lepton flavor-changing neutral current Yukawa couplings. In particular flavor-violating parameters in the quark sector, ${\chi }_{sb}$ and ${\chi }_{db}$, are significantly constrained by present experimental data, whereas the corresponding parameters in the leptonic sector are less constrained.

An unconstrained minimal supersymmetric standard model with the superpartners of the strongly interacting particles very heavy (close to the kinematic reach of the LHC or even beyond it) and a relatively light electroweak sector is considered. Using the event generator Pythia it is shown that the $1\tau \mathrm{\text{−}}\mathrm{\text{jet}}(\mathrm{\text{tagged}})+2l$ and $2\tau \mathrm{\text{−}}\mathrm{\text{jets}}(\mathrm{\text{tagged}})+1l$ signals with a reasonably hard ${\mathrm{E̸}}_T$ spectrum either by themselves or in combination with the conventional $3l$ signal, which is known to be of rather modest size with a soft ${\mathrm{E̸}}_T$ spectrum, may appreciably extend the reach of chargino-neutralino search at the LHC with $10{\mathrm{fb}}^{-1}$ of integrated luminosity. This is especially so if the lighter chargino and the second lightest neutralino decays via two body leptonic modes with large branching ratios. The theoretical motivation of this scenario, yielding large values of the fine-tuning parameters but consistent with various indirect constraints including the dark matter relic density, is briefly discussed. It is shown that in the minimal supergravity model with an universal scalar mass at the grand unified theory scale, the signals involving $\tau$-jets are not viable. Theoretically well-motivated variations of these boundary conditions are, however, adequate for reviving these signals.

We present the light-cone distribution amplitudes of the $\Xi$ baryons up to twist six on the basis of QCD conformal partial wave expansion to the leading order conformal spin accuracy. The nonperturbative parameters relevant to the DAs are determined in the framework of the QCD sum rule. The light-cone QCD sum rule approach is used to investigate both the electromagnetic form factors of $\Xi$ and the exclusive semileptonic decay of ${\Xi }_c$ as applications. Our estimations on the magnetic moments are ${\mu }_{{\Xi }^0}=-(1.92\pm 0.34){\mu }_N$ and ${\mu }_{{\Xi }^{-}}=-(1.19\pm 0.03){\mu }_N$. The decay width of the process ${\Xi }_c\to \Xi e^{+}{\nu }_e$ is evaluated to be $\Gamma =8.73\times {10}^{-14}\mathrm{GeV}$, which is in accordance with the experimental measurements and other theoretical approaches.

We consider the light-front wave function for the valence quark state of mesons using the AdS/CFT correspondence, as has been suggested by Brodsky and Téramond. Two kinds of wave functions, obtained in different holographic Soft-Wall models, are discussed.

Using the binary tetrahedral group $T^{\prime }$, the three angles and phase of the quark CKM mixing matrix are pursued by symmetry-breaking which involves $T^{\prime }$-doublet VEVs and the Chen-Mahanthappa $CP$-violation mechanism. The NMR$T^{\prime }$M, next-to-minimal renormalizable-$T^{\prime }$ model is described, and its one parameter comparison to experimental data is explored.

We compute the longitudinal and Hall conductivities in the parallel phase of the Sakai-Sugimoto model with a transverse magnetic field. We find that the conductivities behave as if the charge of the system is made out of two different types; one behaves as charge carriers flowing through a dissipative neutral medium, while the other does not feel the dissipation. We also investigate the case of an electric field parallel to the magnetic field and find that in this case the system behaves as a perfect conductor. Both of the unusual behaviors stem from the axial anomaly.

We present an explicit formula for the exact rate of pair production of oppositely charged scalar particles by a smooth potential step $\varphi (\mathbf{x})\propto \tanh kz$ in three dimensions. As a check we recover from this the known results for an infinitely sharp step as well as for a uniform electric field.

We investigate new physics effects in the production and detection of high-energy neutrinos at neutrino telescopes. Analyzing the flavor ratios ${\varphi }_{\mu }/{\varphi }_{\tau }$ and ${\varphi }_{\mu }/({\varphi }_{\tau }+{\varphi }_e)$, we find that the standard model predictions for them can be sensibly altered by new physics effects in the case of pion sources. However, the experimental precision required to see the effects would be very difficult to obtain.

We argue that spontaneous Lorentz violation may generally lead to metastable domain walls related to the simultaneous violation of some accompanying discrete symmetries. Remarkably, such domain-wall solutions exist for spacelike Lorentz violation and do not exist for the timelike violation. Because a preferred space direction is spontaneously induced, these domain walls have no planar symmetry and produce a peculiar static gravitational field at small distances, while their long-distance gravity appears the same as for regular scalar-field walls. Some possible applications of vector-field domain walls are briefly discussed.

A coupling system among Gaussian-type microwave photon flux, a static magnetic field, and fractal membranes (or other equivalent microwave lenses) can be used to detect high-frequency gravitational waves (HFGWs) in the microwave band. We study the signal photon flux, background photon flux, and the requisite minimal accumulation time of the signal in the coupling system. Unlike the pure inverse Gertsenshtein effect (G effect) caused by the HFGWs in the gigahertz band, the electromagnetic (EM) detecting scheme proposed by China and the U.S. HFGW groups is based on the composite effect of the synchroresonance effect and the inverse G effect. The key parameter in the scheme is the first-order perturbative photon flux (PPF) and not the second-order PPF; the distinguishable signal is the transverse first-order PPF and not the longitudinal PPF; the photon flux focused by the fractal membranes or other equivalent microwave lenses is not only the transverse first-order PPF but the total transverse photon flux, and these photon fluxes have different signal-to-noise ratios at the different receiving surfaces. Theoretical analysis and numerical estimation show that the requisite minimal accumulation time of the signal at the special receiving surfaces and in the background noise fluctuation would be $\sim {10}^3–{10}^5$ seconds for the typical laboratory condition and parameters of $h_{\mathrm{rms}}\sim {10}^{-26}–{10}^{-30}/\sqrt{\mathrm{Hz}}$ at 5 GHz with bandwidth $\sim 1\mathrm{Hz}$. In addition, we review the inverse G effect in the EM detection of the HFGWs, and it is shown that the EM detecting scheme based only on the pure inverse G effect in the laboratory condition would not be useful to detect HFGWs in the microwave band.

The effects of nonlinear oscillations in compact stars are attracting considerable current interest. In order to study such phenomena in the framework of fully nonlinear general relativity, highly accurate numerical studies are required. A numerical scheme specifically tailored for such a study is based on formulating the time evolution in terms of deviations from a stationary equilibrium configuration. Using this technique, we investigate over a wide range of amplitudes nonlinear effects in the evolution of radial oscillations of neutron stars. In particular, we discuss mode coupling due to nonlinear interaction, the occurrence of resonance phenomena, shock formation near the stellar surface as well as the capacity of nonlinearities to stabilize perturbatively unstable neutron star models.

We study the spectral tilt of primordial perturbations in Hořava-Lifshitz cosmology. The uniform approximation, which is a generalization of the familiar Wentzel-Kramers-Brillouin method, is employed to compute the spectral index both numerically and analytically in a closed form. We clarify how the spectral index depends on the inflation model and parameters in the modified dispersion relation.

According to general relativity a perturbed black hole will settle to a stationary configuration by the emission of gravitational radiation. Such a perturbation will occur, for example, in the coalescence of a black hole binary, following their inspiral and subsequent merger. At late times the waveform is a superposition of quasinormal modes, which we refer to as the ringdown. The dominant mode is expected to be the fundamental mode, $l=m=2$. Since this is a well-known waveform, matched filtering can be implemented to search for this signal using LIGO data. We present a search for gravitational waves from black hole ringdowns in the fourth LIGO science run S4, during which LIGO was sensitive to the dominant mode of perturbed black holes with masses in the range of $10M_{\odot }$ to $500M_{\odot }$, the regime of intermediate-mass black holes, to distances up to 300 Mpc. We present a search for gravitational waves from black hole ringdowns using data from S4. No gravitational wave candidates were found; we place a 90%-confidence upper limit on the rate of ringdowns from black holes with mass between $85M_{\odot }$ and $390M_{\odot }$ in the local universe, assuming a uniform distribution of sources, of $3.2\times {10}^{-5}{\mathrm{yr}}^{-1}{\mathrm{Mpc}}^{-3}=1.6\times {10}^{-3}{\mathrm{yr}}^{-1}{L}_{10}^{-1},$where $L_{10}$ is ${10}^{10}$ times the solar blue-light luminosity.

We explore an extension of the inert doublet model which allows also for $CP$ violation in the Higgs sector. This necessitates two noninert doublets. The lightest neutral scalar of the inert doublet is a candidate for dark matter. Scanning over parameters we preserve the abundance of the dark matter in agreement with the WMAP data. We also impose all relevant collider and theoretical constraints to determine the allowed parameter space for which both the dark matter is appropriate and $CP$ is violated. In addition we find regions where the cutoff of the model originating from naturality arguments can be substantially lifted compared to its standard model value, reaching $\sim 2–3\mathrm{TeV}$.

The lightest neutral scalar in the inert Higgs doublet model is a natural candidate for weakly interacting massive particle dark matter. In this paper, we analyzed the dark matter relic density in the inert Higgs doublet model. Various theoretical and experimental constraints are taken into account. We found that there are five distinctive regions that could provide the right amount of the relic density in the Universe. Four out of those five regions have a light particle spectrum which could be studied at the Large Hadron Collider.