Recent exoplanet surveys have predicted a very large population of planetary systems in our galaxy, more than one planet per star on the average, perhaps totaling about two hundred billion. These surveys, based on electromagnetic observations, are limited to a very small neighborhood of the solar system and the estimations rely on the observations of only a few thousand planets. On the other hand, orbital motions of planets around stars are expected to emit gravitational waves (GW), which could provide information about the planets not accessible to electromagnetic astronomy. The cumulative effect of the planets, with periods ranging from a few hours to several years, is expected to create a stochastic GW background (SGWB). We compute the characteristic GW strain of this background based on the observed distribution of planet parameters. We also show that the integrated extragalactic background is comparable to or less than the galactic background at different frequencies. Our estimate shows that the net background is significantly below the sensitivities of the proposed GW experiments in different frequency bands. However, we notice that the peak of the spectrum, at around ${10}^{-5}\mathrm{Hz}$, is not too far below the proposed space-based GW missions. A future space-based mission may be able to observe or tightly constrain this signal, which will possibly be the only way to probe the galactic population of exoplanets as a whole.

We propose a new method of detecting Ellis wormholes by use of the images of wormholes surrounded by optically thin dust. First, we derive steady solutions of dust and a more general medium surrounding the wormhole by solving relativistic Euler equations. We find two types of dust solutions: one is a static solution with arbitrary density profile, and the other is a solution of dust which passes into the wormhole and escapes into the other side with constant velocity. Next, solving null geodesic equations and radiation transfer equations, we investigate the images of the wormhole surrounded by dust for the above steady solutions. Because the wormhole spacetime possesses unstable circular orbits of photons, a bright ring appears in the image, just as in Schwarzschild spacetime. This indicates that the appearance of a bright ring solely confirms neither a black hole nor a wormhole. However, we find that the intensity contrast between the inside and the outside of the ring are quite different. Therefore, we could tell the difference between an Ellis wormhole and a black hole with high-resolution very-long-baseline-interferometry observations in the near future.

Artificial fragmentation of the matter density field causes the formation of spurious groups of particles in N-body simulations of nonstandard dark matter (DM) models which are characterized by a small scale cutoff in the linear matter power spectrum. These spurious halos alter the prediction of the mass function in a range of masses where differences among DM models are most relevant to observational tests. Using a suite of high resolution simulations we show that the contamination of artificial groups of particles significantly affect the statistics of halo spin, shape and virial state parameters. We find that spurious halos have systematically larger spin values, are highly elliptical or prolate and significantly deviate from virial equilibrium. These characteristics allow us to detect the presence of spurious halos even in nonstandard DM models for which the low-mass end of the mass function remains well behaved. We show that selecting halos near the virial equilibrium provides a simple and effective method to remove the bulk of spurious halos from numerical halo catalogs and consistently recover the halo mass function at low masses.

We consider supersymmetric (SUSY) and non-SUSY models of chaotic inflation based on the ${\varphi }^n$ potential with $2\le n\le 6$. We show that the coexistence of a nonminimal coupling to gravity $f_{\mathcal{R}}=1+c_{\mathcal{R}}{\varphi }^{n/2}$ with a kinetic mixing of the form $f_{\mathrm{K}}=c_{\mathrm{K}}{f}_{\mathcal{R}}^m$ can accommodate inflationary observables favored by the Bicep2/Keck Array and Planck results for $0\le m\le 4$ and $2.5\times {10}^{-4}\le r_{\mathcal{R}\mathrm{K}}=c_{\mathcal{R}}/c_{\mathrm{K}}^{n/4}\le 1$, where the upper limit is not imposed for $n=2$. Inflation can be attained for sub-Planckian inflaton values with the corresponding effective theories retaining the perturbative unitarity up to the Planck scale.

The origin of the most energetic cosmic ray particles is one of the most important open problems in astrophysics. Despite a big experimental effort done in the past years, the sources of these very energetic particles remain unidentified. Therefore, their distribution on the Universe and even their space density are still unknown. It has been shown that different spatial configurations of the sources lead to different energy spectra and composition profiles (in the case of sources injecting heavy nuclei) at Earth. These ensemble fluctuations are more important at the highest energies, because only nearby sources, which are necessarily few, can contribute to the flux observed at Earth. This is due to the interaction of the cosmic rays with the low energy photons of the radiation field, present in the intergalactic medium, during propagation. It is believed that the intergalactic medium is permeated by a turbulent magnetic field. Although at present it is still unknown, there are several constraints for its intensity and coherence length obtained from different observational techniques. Charged cosmic rays are affected by the intergalactic magnetic field because of the bending of their trajectories during propagation through the intergalactic medium. In this work, the influence of the intergalactic magnetic field on the ensemble fluctuations is studied. Sources injecting only protons and only iron nuclei are considered. The ensemble fluctuations are studied for different values of the density of sources compatible with the constraints recently obtained from cosmic ray data. Also, the possible detection of the ensemble fluctuations in the context of the future JEM-EUSO mission is discussed.

We consider a scale invariant extension of the standard model (SM) with a combined breaking of conformal and electroweak symmetry in a strongly interacting hidden $SU(n_c)$ gauge sector with $n_f$ vector-like hidden fermions. The (pseudo) Nambu-Goldstone bosons that arise due to dynamical chiral symmetry breaking are dark matter (DM) candidates. We focus on $n_f=n_c=3$, where $SU(3)$ is the largest symmetry group of hidden flavor which can be explicitly broken into either $U(1)\times U(1)$ or $SU(2)\times U(1)$. We study DM properties and discuss consistent parameter space for each case. Because of different mechanisms of DM annihilation the consistent parameter space in the case of $SU(2)\times U(1)$ is significantly different from that of $SU(3)$ if the hidden fermions have a SM $U(1{)}_Y$ charge of $O(1)$.

We show that new physics can show up in dileptonic events through its radiative contributions to the dilepton invariant mass, leading to unique “monocline” features in $m_{\ell \ell }$, as well as the angular distribution of the leptons. We focus in particular on the case of dark matter with scalar messengers coupling it to the quarks and leptons. Consistent thermal models require the dark matter to have masses of 100s of GeV and have $\gtrsim 1$ couplings to the Standard Model (SM), implying that radiative corrections to the SM Drell-Yan rate can be sizable. We consider the case of Majorana, Dirac, and pseudo-Dirac dark matter and show that there are regions of parameter space where the nonexistence of a monocline, which starts at roughly twice the dark matter mass, $m_{\ell \ell }\sim 2m_{\chi }$, places the strongest constraint on the model. We make predictions for the sensitivities at the high luminosity 14 TeV LHC as well as a future 100 TeV proton-proton collider. We find that our dilepton signal is most sensitive when the mediator and the dark matter are nearly degenerate and conventional missing-transverse-momentum-based searches are least sensitive.

We present a physically motivated parametrization of the chiral-odd generalized parton distributions. The parametrization is an extension of our previous one in the chiral-even sector which was based on the Reggeized diquark model. While for chiral-even generalized distributions a quantitative fit with uncertainty estimation can be performed using deep inelastic scattering data, nucleon electromagnetic, axial and pseudoscalar form factors measurements, and all available deeply virtual Compton scattering data, the chiral-odd sector is far less constrained. While awaiting the analysis of measurements on pseudoscalar mesons exclusive electroproduction which are key for the extraction of chiral-odd GPDs, we worked out a connection between the chiral-even and chiral-odd reduced helicity amplitudes using parity transformations. The connection works for quark-parton models including both scalar and axial vector diquark models, and spectator models in general. This relation allows us to estimate the size of the various chiral-odd contributions and it opens the way for future quantitative fits.

We show that the onset and rise of QCD minijets provide the dynamical mechanism behind the appearance of a soft edge in $pp$ collisions around CERN intersecting storage rings (ISR) energies, and thus such a soft edge is built in our minijet model with soft gluon resummation. Here the model is optimized for the LHC at $\sqrt{s}=7$, 8 TeV and predictions made for higher LHC and cosmic ray energies. Further, we provide a phenomenological picture to discuss the breakup of the total cross section into its elastic, uncorrelated, and correlated inelastic pieces in the framework of a one-channel eikonal function.

We present predictions at next-to-leading order (NLO) accuracy in QCD for top-quark pair production induced by an anomalous chromomagnetic dipole moment of the top quark. Our results are obtained for total as well as fully differential cross sections, including matching to parton shower simulations. This process is expected to provide the most stringent direct limits on top-quark chromomagnetic dipole moment. We find that NLO corrections increase the contribution from the dipole moment by about 50% at the LHC, and significantly reduce the renormalization and factorization scale dependence. Using the NLO prediction, we update the current limit from the Tevatron and the LHC measurements. Apart from total cross section, we also study other observables relevant for LHC phenomenology.

In this work, we consider the further degrees of freedom related to curvature invariants and scalar fields in extended theories of gravity (ETG). These new degrees of freedom can be recast as “effective fluids” that differ in nature with respect to the standard matter fluids generally adopted as sources of the field equations. It is, thus, somewhat misleading to apply the standard general relativistic energy conditions to this effective energy-momentum tensor, as the latter contains the matter content and a geometrical quantity, which arises from the specific ETG considered. Here we explore this subtlety, extending our previous work, in particular, to cases with the contracted Bianchi identities with diffeomorphism invariance and to cases with generalized explicit curvature-matter couplings, which imply the nonconservation of the energy-momentum tensor. Furthermore, we apply the analysis to specific ETGs, such as scalar-tensor gravity and $f(R)$ gravity. Thus, in the context of ETGs, interesting results appear such as matter that may exhibit unusual thermodynamical features, for instance, gravity that retains its attractive character in the presence of large negative pressures; or alternatively, we verify that repulsive gravity may occur for standard matter.

In a draining rotating fluid flow background, surface perturbations behave as a scalar field on a rotating effective black hole spacetime. We propose a new model for the background flow which takes into account the varying depth of the water. Numerical integration of the associated Klein-Gordon equation using accessible experimental parameters shows that gravity waves in an appropriate frequency range are amplified through the mechanism of superradiance. Our numerical results suggest that the observation of this phenomenon in a common fluid mechanical system is within experimental reach. Unlike the case of wave scattering around Kerr black holes, which depends only on one dimensionless background parameter (the ratio $a/M$ between the specific angular momentum and the mass of the black hole), our system depends on two dimensionless background parameters, namely the normalized angular velocity and surface gravity at the effective black hole horizon.

We propose a simple and computationally fast method for performing $N$-body simulations for a large class of modified gravity theories with a screening mechanism such as chameleons, symmetrons, and Galileons. By combining the linear Klein–Gordon equation with a screening factor, calculated from analytical solutions of spherical symmetric configurations, we obtain a modified field equation of which the solution is exact in the linear regime while at the same time taking screening into account on nonlinear scales. The resulting modified field equation remains linear and can be solved just as quickly as the Poisson equation without any of the convergence problems that can arise when solving the full equation. We test our method with $N$-body simulations and find that it compares remarkably well with full simulations well into the nonlinear regime.

Despite numerous efforts, the search for oscillatory signatures in primordial spectra has not produced any convincing evidence for feature models to date. We undertake a thorough search for signatures of sharp features in the WMAP9 power spectrum and bispectrum as well as in the Planck power spectrum. For the first time, we carry out searches in both the power spectrum and bispectrum simultaneously, employing well-defined look-elsewhere statistics to assess significances in a rigorous manner. Developing efficient methods to scan power spectrum likelihoods for oscillatory features, we present results for the phenomenological bare sine and cosine modulations, allowing validation against existing Planck likelihood surveys, as well as templates that include the correct sharp feature scaling. In particular, we study degeneracies between feature and cosmological parameters. For frequencies beyond the scale set by the acoustic peaks, the dependencies are realized through uninteresting adjustments of the comoving distance to last scattering. Hence, it is sufficient to keep cosmological parameters fixed and employ Gaussian approximations to the likelihood as a function of the feature model amplitude. In cases where results can be compared to the literature, our method shows excellent agreement. We supplement results from the Planck likelihood with an analysis based on the Planck spectral matching independent component analysis (SMICA) map that, working on the assumption that the component separation algorithm is reliable, allows for the inclusion of a larger sky fraction. In principle, this allows us to place the most stringent constraints to date on the amplitudes of feature models in the temperature power spectrum. Invoking the WMAP bispectrum, we perform a combined power spectrum and bispectrum survey. We use and slightly generalize statistics developed in previous work to reliably judge the significance of large feature model amplitude estimates. We conclude that our results are entirely consistent with a featureless realization of a Gaussian cosmic microwave background.

The Balitsky-Fadin-Kuraev-Lipatov (BFKL) approach for the investigation of semihard processes is plagued by large next-to-leading corrections, both in the kernel of the universal BFKL Green’s function and in the process-dependent impact factors, as well as by large uncertainties in the renormalization scale setting. All that calls for an optimization procedure of the perturbative series. In this respect, one of the most common methods is the Brodsky-Lepage-Mackenzie (BLM) one, which eliminates the renormalization scale ambiguity by absorbing the nonconformal ${\beta }_0$ terms into the running coupling. In this paper, we apply the BLM scale setting procedure directly to the amplitudes (cross sections) of several semihard processes. We show that, due to the presence of ${\beta }_0$ terms in the next-to-leading expressions for the impact factors, the optimal renormalization scale is not universal but depends both on the energy and on the type of process in question.

The axial-vector-emitting weak hadronic decays of the ${\mathrm{\Omega }}_c^0$ baryon are investigated. After employing the factorization and the pole model framework to predict their branching ratios, we derive the symmetry-breaking effects on axial-vector-meson-baryon couplings and effects of flavor dependence on baryon-baryon weak transition amplitudes and, consequently, on their branching ratios. We found that the W-exchange process contributions dominate $p$-wave-meson emitting decays of the ${\mathrm{\Omega }}_c^0$ baryon.

On the basis of the representation of the generalized structure of nucleons a new model of the hadron interaction at high energies is presented. A new $t$ dependence of the generalized parton distributions is obtained from the comparative analysis of different sets of the parton distribution functions, based on the description of the entire set of experimental data for the electromagnetic form factors of the proton and neutron. Taking into account the different moments of the generalized parton distributions of the hadron, quantitative descriptions of all existing experimental data of the proton-proton and proton-antiproton elastic scatterings from $\sqrt{s}=9.8\mathrm{GeV}$ to 8 TeV, including the Coulomb range and large momentum transfers up to $-t=15{\mathrm{GeV}}^2$, are obtained with a few free high-energy fitting parameters. The real part of the hadronic elastic scattering amplitude is determined only through the complex $s$ that satisfies the dispersion relations. The negligible contributions of the hard Pomeron and the presence of the non-small contributions of the maximal Odderon are obtained. The non-dying form of the spin-flip amplitude is examined as well. The structures of the Born term and unitarized scattering amplitude are analyzed. It is shown that the black disk limit for the elastic scattering amplitude is not reached at LHC energies. Predictions for LHC energies are made.

We study the renormalizability in theories of a self-interacting Lifshitz scalar field. We show that although the statement of power-counting is true at one-loop order, in generic cases where the scalar field is dimensionless, an infinite number of counterterms are involved in the renormalization procedure. This problem can be avoided by imposing symmetries, the shift symmetry in the present paper, which allow only a finite number of counterterms to appear. The symmetry requirements might have important implications for the construction of matter field sectors in the Hořava-Lifshitz gravity.