We propose a charged, electrically neutral, and flavor-changing $Z^{\prime }$ model to conciliate the apparent disagreement between the important excess found in the $t\overline{t}$ Tevatron forward-backward asymmetry and the null—compatible with negative—results found in the LHC charge asymmetry. We show that this model contributes positively to the forward-backward asymmetry, whereas naturally a new cancellation is turned on at the LHC, yielding a null, or even negative, charge asymmetry. We find the region in parameter space that is simultaneously allowed by the stringent Tevatron and LHC observables. We show that the model is safe to atomic parity violation constraints and propose a possible increase in the $Z^{\prime }$ width to avoid restrictions coming from $tj/\overline{t}j$ resonance searches and $t\overline{t}j$ cross section. We evaluate the constraints to the model, as well as distinctive features in the forecoming experimental results.

Nucleon-antinucleon annihilation into a near backward- (or forward-) produced meson and a high invariant mass lepton pair admits a factorized description in terms of antinucleon (or nucleon) distribution amplitudes and nucleon-to-meson (or antinucleon-to-meson) transition distribution amplitudes. We estimate the cross section of backward (and forward) pion and $\eta$-meson production in association with a high invariant mass lepton pair for the kinematical conditions of GSI-FAIR. The cross sections are found to be large enough to be measured with the $\overline{\mathrm{P}}\mathrm{ANDA}$ detector. Interesting phenomenological applications of the approach are thus expected.

We focus on the production of excited neutrinos by ultra high energy (UHE, $E_{\nu }>{10}^4\mathrm{GeV}$) neutrinos traversing the Earth. The surviving neutrino fluxes are calculated using the complete system of transport equations for ordinary neutrinos and their excited states, and we compare these results with the obtained using only Standard Model (SM) interactions. We extend the analysis by including the neutral current (NC) and decay regeneration effects, and computing the surviving flux for different values of $f/\Lambda$, where $\Lambda$ is the compositeness scale and $f$ a coupling factor representing non-perturbative physics. Finally, we analyze the possibilities of detecting such fluxes in a neutrino telescope such as IceCube showing the allowed regions in the $(m^{*},f/\Lambda )$ plane for two possible initial fluxes. We have considered the IC80 configuration of IceCube for an operation time of ten years.

Statistical methods of presenting experimental results in constraining the neutrino mass hierarchy (MH) are discussed. Two problems are considered and are related to each other: how to report the findings for observed experimental data and how to evaluate the ability of a future experiment to determine the neutrino mass hierarchy, namely, the sensitivity of the experiment. For the first problem where experimental data have already been observed, the classical statistical analysis involves constructing confidence intervals for the parameter $\Delta m_{32}^2$. These intervals are deduced from the parent distribution of the estimation of $\Delta m_{32}^2$ based on experimental data. Because of existing experimental constraints on $|\Delta m_{32}^2|$, the estimation of $\Delta m_{32}^2$ is better approximated by a Bernoulli distribution (a binomial distribution with one trial) rather than a Gaussian distribution. Therefore, the Feldman-Cousins approach needs to be used instead of the Gaussian approximation in constructing confidence intervals. Furthermore, as a result of the definition of confidence intervals, even if it is correctly constructed, its confidence level does not directly reflect how much one hypothesis of the MH is supported by the data rather than the other hypothesis. We thus describe a Bayesian approach that quantifies the evidence provided by the observed experimental data through the (posterior) probability that either hypothesis of MH is true. This Bayesian presentation of observed experimental results is then used to develop several metrics to assess the sensitivity of future experiments. Illustrations are made by using a simple example with a confined parameter space, which approximates the MH determination problem with experimental constraints on the $|\Delta m_{32}^2|$.

We propose a new $CPT$-even and Lorentz-violating nonminimal coupling between fermions and Abelian gauge fields involving the $CPT$-even tensor $(K_F{)}_{\mu \nu \alpha \beta }$ of the standard model extension. We thus investigate its effects on the cross section of the electron-positron scattering by analyzing the process $e^{+}+e^{-}\to {\mu }^{+}+{\mu }^{-}$. Such a study was performed for the parity-odd and parity-even nonbirefringent components of the Lorentz-violating $(K_F{)}_{\mu \nu \alpha \beta }$ tensor. Finally, by using experimental data available in the literature, we have imposed upper bounds as tight as ${10}^{-12}(\mathrm{eV}{)}^{-1}$ on the magnitude of the $CPT$-even and Lorentz-violating parameters while nonminimally coupled.

We calculate the number density, energy density, transverse pressure, longitudinal pressure, and magnetization of an ensemble of spin one-half particles in the presence of a homogenous background magnetic field. The magnetic field direction breaks spherical symmetry causing the pressure transverse to the magnetic field direction to be different than the pressure parallel to it. We present explicit formulas appropriate at zero and finite temperature for both charged and uncharged particles including the effect of the anomalous magnetic moment. We demonstrate that the resulting expressions satisfy the canonical relations $\Omega =-P_{\parallel }$ and $P_{\perp }=P_{\parallel }-MB$, with $M=-\partial \Omega /\partial B$ being the magnetization of the system. We numerically calculate the resulting pressure anisotropy for a gas of protons and a gas of neutrons and demonstrate that the inclusion of the anomalous magnetic increases the level of pressure anisotropy in both cases.

To study the capabilities of supernova neutrino detectors, the instantaneous spectra are often represented by a quasithermal distribution of the form $f_{\nu }(E)\propto E^{\alpha }{e}^{-(\alpha +1)E/E_{\mathrm{av}}}$, where $E_{\mathrm{av}}$ is the average energy and $\alpha$ a numerical parameter. Based on a spherically symmetric supernova model with full Boltzmann neutrino transport we have, at a few representative postbounce times, reconverged the models with vastly increased energy resolution to test the fit quality. For our examples, the spectra are well represented by such a fit in the sense that the counting rates for a broad range of target nuclei, sensitive to different parts of the spectrum, are reproduced very well. Therefore, the mean energy and root-mean-square energy of numerical spectra hold enough information to provide the correct $\alpha$ and to forecast the response of multichannel supernova neutrino detection.

The Bethe-Salpeter equation and leptonic decay constants for pseudoscalar and vector quark-antiquark mesons with arbitrary quark masses are studied in Coulomb gauge, under a leading order truncation. As input, we use a pure linear rising potential, supplemented by a contact term arising from the conservation of total color charge. It is shown how the equations can be written in terms of manifestly finite functions, despite the infrared singular interaction. The resulting equations are solved numerically. Both the pattern of dynamical chiral symmetry breaking and the leading order heavy quark limit are visible.

We introduce a new class of two-dimensional diagrams, the projection diagrams, as a tool to visualize the global structure of space-times. We construct the diagrams for several metrics of interest, including the Kerr-Newman-(anti)de Sitter family, with or without cosmological constant, and the Emparan-Reall black rings.

Quantum gravity theory is untested experimentally. Could it be tested with tabletop experiments? While the common feeling is pessimistic, a detailed inquiry shows it possible to sidestep the onerous requirement of localization of a probe on the Planck length scale. I suggest a tabletop experiment which, given state-of-the-art ultrahigh vacuum and cryogenic technology, could already be sensitive enough to detect Planck scale signals. The experiment combines a single photon’s degree of freedom with that of a macroscopic probe to test Wheeler’s conception of “quantum foam,” the assertion that on length scales of the Planck order, spacetime is no longer a smooth manifold. The scheme makes few assumptions beyond energy and momentum conservations, and is not based on a specific quantum gravity scheme.

In supersymmetric models of warm inflation, the large temperature of the radiation bath produced by the dissipative motion of the inflaton field may induce a significant thermal abundance of potentially dangerous gravitinos. While previous discussions of this problem focused on gravitino production only at the end of warm inflation, similarly to conventional reheating scenarios, we study the full evolution of the gravitino abundance during and after inflation for simple monomial potentials, taking into account the enhanced gravitino and possibly gaugino masses due to supersymmetry breaking during inflation and the smooth transition into a radiation-dominated era. We find, on one hand, that the continuous thermal production increases the gravitino yield, although, on the other hand, “freeze-out” occurs at temperatures much lower than previously estimated. Moreover, for sufficiently strong dissipation, which allows for sub-Planckian inflaton values, the lower radiation temperature significantly alleviates and possibly solves the gravitino problem, with a baryon asymmetry being nevertheless produced through dissipative effects. Our analysis may also be relevant to standard reheating as an oscillating inflaton will also change the gravitino mass, potentially modifying the produced gravitino yield.

In this paper we present the implementation of an efficient formalism for the generation of arbitrary non-Gaussian initial conditions for use in N-body simulations. The methodology involves the use of a separable modal approach for decomposing a primordial bispectrum or trispectrum. This approach allows for the far more efficient generation of the non-Gaussian initial conditions already described in the literature, as well as the generation for the first time of nonseparable bispectra and the special class of diagonal-free trispectra. The modal approach also allows for the reconstruction of the spectra from given realizations, a fact which is exploited to provide an accurate consistency check of the simulations.

The Korteweg-de Vries equation is a nonlinear wave equation that has played a fundamental role in diverse branches of mathematical and theoretical physics. In the present paper, we consider its significance to cosmology. It is found that the Korteweg-de Vries equation arises in a number of important scenarios, including inflationary cosmology, the cyclic universe, loop quantum cosmology and braneworld models. Analogies can be drawn between cosmic dynamics and the propagation of the solitonic wave solution to the equation, whereby quantities such as the speed and amplitude profile of the wave can be identified with cosmological parameters such as the spectral index of the density perturbation spectrum and the energy density of the universe. The unique mathematical properties of the Schwarzian derivative operator are important to the analysis. A connection with dark solitons in Bose-Einstein condensates is briefly discussed.

We investigate the possibility that the galactic dark matter exists in a scenario where the phantom field is responsible for the dark energy. We obtain the statically and spherically approximate solution for this kind of galaxy system with a supermassive black hole at its center. The solution of the metric functions is satisfied with $g_{tt}=-g_{rr}^{-1}$. Constrained by the observation of the rotational stars moving in circular orbits with nearly constant tangential speed in a spiral galaxy, the background of the phantom field which is spatially inhomogeneous has an exponential potential. To avoid the well-known quantum instability of the vacuum at high frequencies, the phantom field defined in an effective theory is valid only at low energies. Under this assumption, we further investigate the following properties. The absorption cross section of the low-energy $S$-wave excitations of the phantom field into the central black hole is shown to be the horizontal area of the central black hole. Because the infalling phantom particles have a total negative energy, the accretion of the phantom energy is related to the decrease of the black hole mass, which is estimated to be much less than a solar mass in the lifetime of the Universe. Using a simple model with the cold dark matter very weakly coupled to the “low-frequency” phantom particles that are generated from the background, we show that these two densities can be quasistable in the galaxy.

We present a detection of the unnormalized skewness $⟨{\tilde{T}}^3(\widehat{\mathbf{n}})⟩$ induced by the thermal Sunyaev-Zel’dovich (tSZ) effect in filtered Atacama Cosmology Telescope (ACT) 148 GHz cosmic microwave background temperature maps. Contamination due to infrared and radio sources is minimized by template subtraction of resolved sources and by constructing a mask using outlying values in the 218 GHz (tSZ-null) ACT maps. We measure $⟨{\tilde{T}}^3(\widehat{\mathbf{n}})⟩=-31\pm 6\mu {\mathrm{K}}^3$ (Gaussian statistics assumed) or $\pm 14\mu {\mathrm{K}}^3$ (including non-Gaussian corrections) in the filtered ACT data, a $5\sigma$ detection. We show that the skewness is a sensitive probe of ${\sigma }_8$, and use analytic calculations and tSZ simulations to obtain cosmological constraints from this measurement. From this signal alone we infer a value of ${\sigma }_8={0.79}_{-0.03}^{+0.03}$ (68% C.L.) ${\text{}}_{-0.06}^{+0.06}$ (95% C.L.). Our results demonstrate that measurements of non-Gaussianity can be a useful method for characterizing the tSZ effect and extracting the underlying cosmological information.

Neutron star binaries offer a rich phenomenology in terms of gravitational waves and merger remnants. However, most general relativistic studies have been performed for nearly circular binaries, with the exception of head-on collisions. We present the first numerical relativity investigation of mergers of eccentric equal-mass neutron star binaries that probes the regime between head-on and circular. In addition to gravitational waves generated by the orbital motion, we find that the signal also contains a strong component due to stellar oscillations ($f$ modes) induced by tidal forces, extending a classical result for Newtonian binaries. The merger can lead to rather massive disks on the order of 10% of the total initial mass.

Kinematic distributions in the decays of the newly discovered resonance to four leptons can provide a direct measurement of the tensor structure of the particle’s couplings to gauge bosons. Even if the particle is shown to be a parity even scalar, measuring this tensor structure is a necessary step in determining if this particle is responsible for giving mass to the $Z$. We consider a Standard Model–like coupling as well as coupling via a dimension five operator to either $ZZ$ or $Z\gamma$. We show that using full kinematic information from each event allows discrimination between renormalizable and higher dimensional coupling to $ZZ$ at the 95% confidence level with $\mathcal{O}(50)$ signal events, and coupling to $Z\gamma$ can be distinguished with as few as 20 signal events. This shows that these measurements can be useful possibly even with this year’s LHC data.

Using an $SU(3)$ flavor symmetry breaking expansion in the quark mass, we determine the QCD component of the nucleon, Sigma and Xi mass splittings of the baryon octet due to up-down (and strange) quark mass differences in terms of the kaon mass splitting. Provided the average quark mass is kept constant, the expansion coefficients in our procedure can be determined from computationally cheaper simulations with mass-degenerate sea quarks and partially quenched valence quarks. Both the linear and quadratic terms in the $SU(3)$ flavor symmetry breaking expansion are considered; it is found that the quadratic terms only change the result by a few percent, indicating that the expansion is highly convergent.

Contributions of strange quarks to the mass and spin of the nucleon, characterized by the observables $f_{T_s}$ and $\Delta s$, respectively, are investigated within lattice QCD. The calculation employs a ($2+1$)-flavor mixed-action lattice scheme, thus treating the strange quark degrees of freedom in dynamical fashion. Numerical results are obtained at three pion masses, $m_{\pi }=495$, 356, and 293 MeV, renormalized, and chirally extrapolated to the physical pion mass. The value extracted for $\Delta s$ at the physical pion mass in the $\overline{\mathrm{MS}}$ scheme at a scale of 2 GeV is $\Delta s=-0.031(17)$, whereas the strange quark contribution to the nucleon mass amounts to $f_{T_s}=0.046(11)$. In the employed mixed-action scheme, the nucleon valence quarks as well as the strange quarks entering the nucleon matrix elements that determine $f_{T_s}$ and $\Delta s$ are realized as domain wall fermions, propagators of which are evaluated in MILC ($2+1$)-flavor dynamical asqtad quark ensembles. The use of domain wall fermions leads to mild renormalization behavior, which proves especially advantageous in the extraction of $f_{T_s}$.

We present $2+1$ flavor lattice QCD calculations of the nucleon scalar and tensor charges. Using the BMW clover-improved Wilson action with pion masses between 149 and 356 MeV and three source-sink separations between 0.9 and 1.4 fm, we achieve good control over excited-state contamination and extrapolation to the physical pion mass. As a consistency check, we also present results from calculations using unitary domain wall fermions with pion masses between 297 and 403 MeV, and using domain wall valence quarks and staggered sea quarks with pion masses between 293 and 597 MeV.