We prove the nonexistence of a nontrivial integral that is a polynomial in momenta of degree $\le 6$ for the Zipoy-Voorhees spacetime with the parameter $\delta =2$.

In this paper we examine the extent to which black hole quasinormal modes (QNMs) could be used to test the no-hair theorem with future ground- and space-based gravitational-wave detectors. We model departures from general relativity (GR) by introducing extra parameters which change the mode frequencies or decay times from their values in GR. With the aid of Bayesian model selection, we assess the extent to which the presence of such a parameter could be inferred, and its value estimated. We find that it is harder to measure the departure of the mode decay times from their GR values than it is with the mode frequencies. The Einstein Telescope (ET, a third generation ground-based detector) could detect departures of as little as 8% in the frequency of the dominant QNM mode of a $500M_{\odot }$ black hole, out to a maximum range of $\simeq 6\mathrm{Gpc}$ ($z\simeq 0.91$). The New Gravitational Observatory (NGO, an ESA space mission to detect gravitational waves) can detect departures of $\sim 0.6\%$ in a ${10}^8{M}_{\odot }$ black hole to a luminosity distance of 50 Gpc ($z\simeq 5.1$), and departures of $\sim 10\%$ in a ${10}^6{M}_{\odot }$ black hole to a luminosity distance of $\simeq 6\mathrm{Gpc}$. In this exploratory work we have made a specific choice of source position (overhead), orientation (inclination angle of $\pi /3$) and mass ratio of progenitor binary ($m_1/m_2=2$). A more exhaustive Monte Carlo simulation that incorporates progenitor black hole spins and a hierarchical model for the growth of massive black holes is needed to evaluate a more realistic picture of the possibility of ET and NGO to carry out such tests.

We consider the minimally coupled 3-form field, which has been considered as a candidate for realizing inflation. We have studied the conditions to avoid ghosts and Laplacian instabilities and found that some classes of potentials, e.g., the Mexican-hat, will in general be unstable. We then propose other classes of potentials which are instead free from any instability, drive a long enough slow-roll regime followed by an oscillatory epoch, and as a consequence, can provide successful inflation. Finally, we also provide stable potentials that lead to a small enough propagation speed for the scalar perturbations, making it possible for these models to produce non-Gaussianities.

A self-consistent account of the most simple nongauge vector fields leads to a broad spectrum of regular scenarios of the temporal evolution of the Universe completely within the frames of Einstein’s general relativity. The longitudinal nongauge vector field is “the missing link in the chain,” displaying the repulsive elasticity and allowing the macroscopic description of the main features of the Universe’s evolution. The singular big bang turns into a regular inflation-like state of maximum compression with the further accelerated expansion at late times. The parametric freedom of the theory allows us to forget the troubles of fine-tuning. In the most interesting cases the analytical solutions of Einstein’s equations are found.

We study the spectra of gamma ray signals that arise from dark matter annihilation in the Universe. We focus on the large class of theories where the photon spectrum includes both continuum spectrum of gamma rays that arise from annihilation into standard model states at tree level, as well as monochromatic gamma rays arising from annihilation directly into two photons at the one-loop level. In this class of theories we obtain lower bounds on the ratio of the strength of the gamma ray line relative to the gamma ray continuum as a function of the dark matter mass and spin. These limits are obtained from the unitarity relation between the tree-level amplitude of the primary annihilation channel and the imaginary part of the loop-level amplitude for annihilation directly into photons, with the primary decay products running in the loop. These results are exact in the limit that dark matter annihilation at tree level is exclusively to a single standard model species, occurs through the lowest partial wave and respects $CP$. Away from this limit the bounds are approximate. Our conclusions agree with known results in the literature for the cases of the minimal supersymmetric standard model, universal extra dimensions and the littlest Higgs with $T$ parity. We use the Fermi-LAT observations to translate these limits into upper bounds on the dark matter annihilation cross section into any specific standard model state.

A universe filled with a homogeneous scalar field exhibits “cosmological hysteresis.” Cosmological hysteresis is caused by the asymmetry in the equation of state during expansion and contraction. This asymmetry results in the formation of a hysteresis loop: $\oint pdV$, whose value can be nonvanishing during each oscillatory cycle. For flat potentials, a negative value of $\oint pdV$ leads to the increase in amplitude of consecutive cycles and to a universe with older and larger successive cycles. Such a universe appears to possess an arrow of time even though entropy production is absent and all of the equations respect time-reversal symmetry. Cosmological hysteresis appears to be widespread and exists for a large class of scalar-field potentials and mechanisms for making the universe bounce. For steep potentials, the value of $\oint pdV$ can be positive as well as negative. The expansion factor in this case displays quasiperiodic behavior in which successive cycles can be both larger as well as smaller than previous ones. This quasiregular pattern resembles the phenomenon of beats displayed by acoustic systems. Remarkably, the expression relating the increase or decrease in oscillatory cycles to the quantum of hysteresis appears to be model independent. The cyclic scenario is extended to spatially anisotropic models and it is shown that the anisotropy density decreases during successive cycles if $\oint pdV$ is negative.

We study both oscillating and inflating curvaton scenarios when the curvaton mechanism is caused by a hybrid potential. The source of the curvature perturbation is the inhomogeneous phase transition that causes the modulation of the onset of the oscillation. For the supergravity-motivated curvaton there is a possibility of finding natural coincidence of the energy density that is needed to affect non-Gaussianity in the curvaton scenario.

Thompson scattering of cosmic microwave background (CMB) photons off of free electrons during the reionization epoch induces a correlation between the distribution of galaxies and the polarization pattern of the CMB, the magnitude of which is proportional to the quadrupole moment of radiation at the time of scattering. Since the quadrupole moment generated by gravitational waves (GWs) gives rise to a different polarization pattern than that produced by scalar modes, one can put interesting constraints on the strength of GWs on large scales by cross correlating the small scale galaxy distribution and CMB polarization. We use this method together with Fisher analysis to predict how well future surveys can measure the tensor-to-scalar ratio $r$. We find that with a future CMB experiment with detector noise ${\Delta }_P=2\mu \mathrm{K}\mathrm{\text{−}}\mathrm{arcmin}$ and a beam width ${\theta }_{\mathrm{FWHM}}=2^{\prime }$ and a future galaxy survey with limiting magnitude $I<25.6$ one can measure the tensor-to-scalar ratio with an error ${\sigma }_r\simeq 0.09$. To measure $r\approx 0.01$, however, one needs ${\Delta }_P\simeq 0.5\mu \mathrm{K}\mathrm{\text{−}}\mathrm{arcmin}$ and ${\theta }_{\mathrm{FWHM}}\simeq 1^{\prime }$. We also investigate a few systematic effects, none of which turn out to add any biases to our estimators, but they increase the error bars by adding to the cosmic variance. The incomplete sky coverage has the most dramatic effect on our constraints on $r$ for large sky cuts, with a reduction in signal-to-noise smaller than one would expect from the naive estimate $(\frac{S}{N}{)}^2\propto f_{\mathrm{sky}}$. Specifically, we find a degradation factor of $f_{\mathrm{deg}}=0.32\pm 0.01$ for a sky cut of $|b|>10°$ ($f_{\mathrm{sky}}=0.83$) and $f_{\mathrm{deg}}=0.056\pm 0.004$ for a sky cut of $|b|>20°$ ($f_{\mathrm{sky}}=0.66$). Nonetheless, given that our method has different systematics than the more conventional method of observing the large scale $B$ modes directly, it may be used as an important check in the case of a detection.

We consider holographic cosmological models of dark energy in which the infrared cutoff is set by the Hubble’s radius. We show that any interacting dark energy model with a matterlike term able to alleviate the coincidence problem (i.e., with a positive interaction term, regardless of its detailed form) can be recast as a noninteracting model in which the holographic parameter $c^2$ evolves slowly with time. Two specific cases are analyzed. First, the interacting model presented by Duran, Pavón, and Zimdahl [J. Cosmol. Astropart. Phys. 07 (2010) 018.] is considered, and its corresponding noninteracting version found. Then, a new noninteracting model, with a specific $c^2(z)$ expression, is proposed and analyzed along with its corresponding interacting version. We constrain the parameters of both models using observational data and show that they can be distinguished at the perturbative level.

A dependence of the neutrino masses on the dark energy scalar field could provide a solution to the why now problem of dark energy. The dynamics of the resulting cosmological model—growing neutrino quintessence—include an attractive force between neutrinos substantially stronger than gravity. We present a comprehensive approach towards an understanding of the full cosmological evolution, including the formation of large-scale neutrino structures. Important effects we account for are local variations in the dark energy and the backreaction on the background evolution, as well as relativistic neutrino velocities. For this aim, we develop a relativistic $N$-body treatment of the neutrinos combined with an explicit computation of the local quintessence field. At its current stage, the simulation method is successful until $z\approx 1$ and reveals a rich phenomenology. We obtain a detailed picture of the formation of large-scale neutrino structures and their influence on the evolution of matter, dark energy, and the late-time expansion of the Universe.

The effects of Lorentz-violating operators of nonrenormalizable dimension in optical resonate cavities are studied. Optical-frequency experiments are shown to provide sensitivity to nondispersive nonbirefringent violations that is many orders of magnitude beyond current constraints from microwave cavities. Existing experiments based on Fabry-Pérot and ring resonators are considered as illustrations.

The seeming violation of universality in the $\tau$ lepton coupling to the $W$ boson suggested by LEP-II data is studied using an effective field theory (EFT) approach. Within this framework we explore how this feature fits into the current constraints from electroweak precision observables using different assumptions about the flavor structure of New Physics, namely $[U(2)\times U(1){]}^5$ and $U(2{)}^5$. We show the importance of leptonic and semileptonic tau decay measurements, giving 3–4 TeV bounds on the New Physics effective scale at 90% C.L. We conclude under very general assumptions that it is not possible to accommodate this deviation from universality in the EFT framework, and thus such a signal could only be explained by the introduction of light degrees of freedom or New Physics strongly coupled at the electroweak scale.

The rare semileptonic $B_c\to D_s^{*}{\ell }^{+}{\ell }^{-}$ decay is studied in the scenario of the universal extra dimension model with a single extra dimension in which the inverse of the compactification radius $R$ is the only new parameter. The sensitivity of differential branching ratio, total branching ratio, polarization, and forward-backward asymmetries of final state leptons, both for muon and tau, to the compactification parameter is presented. For some physical observables, the uncertainty on the form factors and resonance contributions have been considered in the calculations. The obtained results, compared with the available data, show that new contributions appear due to the extra dimension.

We study Higgs-radion mixing in a warped extra-dimensional model with standard model fields in the bulk, and we include a fourth generation of chiral fermions. The main problem with the fourth generation is that, in the absence of Higgs-radion mixing, it produces a large enhancement in the Higgs production cross section, now severely constrained by LHC data. We analyze the production and decay rates of the two physical states emerging from the mixing and confront them with present LHC data. We show that the current signals observed can be compatible with the presence of one, or both, of these Higgs-radion mixed states (the $\varphi$ and the $h$), although with a severely restricted parameter space. In particular, the radion interaction scale must be quite low, ${\Lambda }_{\varphi }\sim 1–1.5\mathrm{TeV}$. If $m_{\varphi }\sim 125\mathrm{GeV}$, the $h$ state must be heavier ($m_h>320$). If $m_h\sim 125\mathrm{GeV}$, the $\varphi$ state must be quite light or close in mass ($m_{\varphi }\sim 120\mathrm{GeV}$). We also present the modified decay branching ratios of the mixed Higgs-radion states, including flavor-violating decays into fourth-generation quarks and leptons. The windows of allowed parameter space obtained are very sensitive to the increased precision of upcoming LHC data. During the present year, a clear picture of this scenario will emerge, either confirming or further severely constraining this scenario.

Baryon number violating interactions could modify the signatures of supersymmetric models at the Large Hadron Collider. In this article we investigate the predictions for the Higgs mass and the Higgs decays in a simple extension of the minimal supersymmetric standard model where the local baryon and lepton numbers are spontaneously broken at the TeV scale. This theory predicts baryon number violation at the low scale that can change the current LHC bounds on the supersymmetric spectrum. Using the ATLAS and CMS bounds on the Higgs mass we show the constraints on the sfermion masses and show the subsequent predictions for the radiative Higgs decays. We found that the Higgs decay into two photons is suppressed due to the existence of new light leptons. In this theory the stops can be very light in agreement with all experimental bounds, and we make a brief discussion of the possible signals at the LHC.

Recently the ATLAS and CMS experiments have presented data hinting at the presence of a Higgs boson at $m_h\simeq 125\mathrm{GeV}$. The best-fit $h\to \gamma \gamma$ rate averaged over the two experiments is approximately $2.1\pm 0.5$ times the standard model prediction. We study the possibility that the excess relative to the standard model is due to $h\to aa$ decays, where $a$ is a light pseudoscalar that decays predominantly into $\gamma \gamma$. Although this process yields $4\gamma$ final states, if the pseudoscalar has a mass of the order tens of MeV, the two photons from each $a$ decay can be so highly collimated that they may be identified as a single photon. Some fraction of the events then contribute to an effective $h\to \gamma \gamma$ signal. We study the constraints on the parameter space where the net $h\to \gamma \gamma$ rate is enhanced over the standard model by this mechanism and describe some simple models that give rise to the pseudoscalar-photon interaction. Further tests and prospects for searches in the near future are discussed.

Within the $R$-parity violating minimal supersymmetric standard model, we use a hierarchical ansatz for the lepton-number violating trilinear Yukawa couplings by relating them to the corresponding Higgs-Yukawa couplings. This ansatz reduces the number of free parameters in the lepton-number violating sector from 36 to 6. Baryon-number violating terms are forbidden by imposing the discrete gauge symmetry baryon triality. We fit the lepton-number violating parameters to the most recent neutrino oscillation data, including the mixing angle ${\theta }_{13}$ found by Daya Bay. We find that we obtain phenomenologically viable neutrino masses and mixings only in the case of normal ordered neutrino masses and that the lepton-number violating sector is unambiguously determined by neutrino oscillation data. We discuss the resulting collider signals for the case of a neutralino as well as a scalar tau lightest supersymmetric particle. We use the ATLAS searches for multijet events and large transverse missing momentum in the 0, 1, and 2 lepton channel with 7 TeV center-of-mass energy in order to derive exclusion limits on the parameter space of this $R$-parity violating supersymmetric model.

Supersymmetric models with extended electroweak gauge groups have the potential to enhance the Higgs quartic interaction through nondecoupling D-terms. We consider the D-term enhancement effect in a vector top partner model, where the quadratic divergence to the Higgs mass from the virtual top quark is canceled by its corresponding spin-1 superpartners. We are going to show that the model can predict a Higgs mass beyond the LEP bound and is consistent with the precision electroweak constraints.

We discuss the spin structure of the proton in a light-cone treatment of the chiral quark model. Based on the fact that the quark helicity ($\Delta q$) measured in polarized deep inelastic scattering experiments is actually the quark spin defined in the light-cone formalism rather than the quark spin ($\Delta q_{QM}$) defined in the conventional quark model (or in the rest frame of the nucleon), we calculate the $x$ dependence of the polarized quark distribution functions $\Delta q(x)$, and the polarized structure functions $g_1(x)$. Special attention is focused on the Melosh-Wigner rotation due to the transversal motions of quarks inside the nucleon and Melosh-Wigner rotation effects on the bare quark input. It is shown that our results match the experimental data well.

In this work we present a general derivation of relativistic fluid dynamics from the Boltzmann equation using the method of moments. The main difference between our approach and the traditional 14-moment approximation is that we will not close the fluid-dynamical equations of motion by truncating the expansion of the distribution function. Instead, we keep all terms in the moment expansion. The reduction of the degrees of freedom is done by identifying the microscopic time scales of the Boltzmann equation and considering only the slowest ones. In addition, the equations of motion for the dissipative quantities are truncated according to a systematic power-counting scheme in Knudsen and inverse Reynolds number. We conclude that the equations of motion can be closed in terms of only 14 dynamical variables, as long as we only keep terms of second order in Knudsen and/or inverse Reynolds number. We show that, even though the equations of motion are closed in terms of these 14 fields, the transport coefficients carry information about all the moments of the distribution function. In this way, we can show that the particle-diffusion and shear-viscosity coefficients agree with the values given by the Chapman-Enskog expansion.