The earlier search at HERMES for narrow baryon states excited in quasireal photoproduction, decaying through the channel $p{K}_{\mathrm{S}}^0\to p{\pi }^{+}{\pi }^{-}$, has been extended with improved decay-particle reconstruction, more advanced particle identification, and increased event samples. The structure observed earlier at an invariant mass of 1528 MeV shifts to 1522 MeV and the statistical significance drops to about $2\sigma$ for data taken with a deuterium target. The number of events above background is $68_{-31}^{+98}(\text{stat})\pm 13(\text{sys})$. No such structure is observed in the hydrogen data set.

We study QCD radiation for the $WH$ and $WZ$ production processes at the LHC. We identify the regions sensitive to anomalous couplings, by considering jet observables, computed at next-to-leading-order QCD with the use of the Monte Carlo program vbfnlo. Based on these observations, we propose the use of a dynamical jet veto. The dynamical jet veto avoids the problem of large logarithms depending on the veto scale, hence providing more reliable predictions and simultaneously increasing the sensitivity to anomalous coupling searches, especially in the $WZ$ production process.

Based on a sample of 500 million $e^{+}{e}^{-}\to c\overline{c}$ events recorded by the BABAR detector at c.m. energies of close to 10.6 GeV, we report on a study of the decay $D^0\to {\pi }^{-}{e}^{+}{\nu }_e$. We measure the ratio of branching fractions, $R_D=\mathcal{B}(D^0\to {\pi }^{-}{e}^{+}{\nu }_e)/\mathcal{B}(D^0\to K^{-}{\pi }^{+})=0.0713\pm 0.0017_{\text{stat}}\pm 0.0024_{\text{syst}}$, and use the present world average for $\mathcal{B}(D^0\to K^{-}{\pi }^{+})$ to obtain $\mathcal{B}(D^0\to {\pi }^{-}{e}^{+}{\nu }_e)=(2.770\pm 0.068_{\text{stat}}\pm 0.092_{\text{syst}}\pm 0.037_{\text{ext}})\times 10^{-3}$ where the third error accounts for the uncertainty on the branching fraction for the reference channel. The measured dependence of the differential branching fraction on $q^2$, the four-momentum transfer squared between the $D$ and the $\pi$ meson, is compared to various theoretical predictions for the hadronic form factor, $f_{+,D}^{\pi }(q^2)$, and the normalization $|V_{cd}|\times f_{+,D}^{\pi }(q^2=0)=0.1374\pm 0.0038_{\text{stat}}\pm 0.0022_{\text{syst}}\pm 0.0009_{\text{ext}}$. is extracted from a fit to data. Using the most recent LQCD prediction of $f_{+,D}^{\pi }(q^2=0)=0.666\pm 0.029$, we obtain $|V_{cd}|=0.206\pm 0.007_{\text{exp}}\pm 0.009_{\mathrm{LQCD}}$. Assuming, instead, $|V_{cd}|=|V_{us}|=0.2252\pm 0.0009$, we obtain $f_{+,D}^{\pi }(q^2=0)=0.610\pm 0.020_{\text{exp}}\pm 0.005_{\text{ext}}$. The $q^2$ dependence of $f_{+,D}^{\pi }(q^2)$ is compared to a variety of multipole parametrizations. This information is applied to $B^0\to {\pi }^{-}{e}^{+}{\nu }_e$ decays and, combined with an earlier $B^0\to {\pi }^{-}{e}^{+}{\nu }_e$ measurement by BABAR, is used to derive estimates of $|V_{ub}|$.

We revisit Ozawa’s uncertainty principle (OUP) in the framework of noncommutative (NC) quantum mechanics. We derive a matrix version of OUP accommodating any NC structure in the phase space, and compute NC corrections to lowest order for two measurement interactions, namely the backaction evading quadrature amplifier and noiseless quadrature transducers. These NC corrections alter the nature of the measurement interaction, as a noiseless interaction may acquire noise, and an interaction of independent intervention may become dependent on the object system. However the most striking result is that noncommutativity may lead to a violation of the OUP itself. The NC corrections for the backaction evading quadrature amplifier reveal a new term which may potentially be amplified in such a way that the violation of the OUP becomes experimentally testable. On the other hand, the NC corrections to the noiseless quadrature transducer shows an incompatibility of this model with NC quantum mechanics. We discuss the implications of this incompatibility for NC quantum mechanics and for Ozawa’s uncertainty principle.

We study a lattice field theory model containing two flavors of massless staggered fermions with an onsite four-fermion interaction. The model contains an SU(4) symmetry which forbids nonzero fermion bilinear mass terms, due to which there is a massless fermion phase at weak couplings. However, even at strong couplings fermion bilinear condensates do not appear in our model, although fermions do become massive. While the existence of this exotic strongly coupled massive fermion phase was established long ago, the nature of the transition between the massless and the massive phase has remained unclear. Using Monte Carlo calculations in three space-time dimensions, we find evidence for a direct second-order transition between the two phases suggesting that the exotic lattice phase may have a continuum limit at least in three dimensions. A similar exotic second-order critical point was found recently in a bilayer system on a honeycomb lattice.

Gravitational theories with fixed background fields break local Lorentz and diffeomorphism invariance either explicitly or spontaneously. In the case of explicit breaking it is known that conflicts can arise between the dynamics and geometrical constraints, while spontaneous breaking evades this problem. It is for this reason that in the gravity sector of the Standard-Model extension (SME) it is assumed that the background fields (SME coefficients) originate from spontaneous symmetry breaking. However, in other examples, such as Chern-Simons gravity and massive gravity, diffeomorphism invariance is explicitly broken by the background fields, and the potential conflicts between the dynamics and geometry can be avoided in most cases. An analysis of how this occurs is given, and the conditions that are placed on the metric tensor and gravitational structure as a result of the presence of an explicit-breaking background are described. The gravity sector of the SME is then considered for the case of explicit breaking. However, it is found that a useful post-Newtonian limit is only obtained when the symmetry breaking is spontaneous.

The Blandford-Znajek (BZ) mechanism describes a physical process for the energy extraction from a spinning black hole (BH), which is believed to power a great variety of astrophysical sources, such as active galactic nuclei and gamma ray bursts. The only known analytic solution to the BZ mechanism is a split monopole perturbation solution up to $O(a^2)$, where $a$ is the spin parameter of a Kerr black hole. In this paper, we extend the monopole solution to higher order $\sim O(a^4)$. We carefully investigate the structure of the BH magnetosphere, including the angular velocity of magnetic field lines $\mathrm{\Omega }$, the toroidal magnetic field $B^{\varphi }$, as well as the poloidal electric current $I$. In addition, the relevant energy extraction rate $\dot{E}$ and the stability of this high-order monopole perturbation solution are also examined.

Solution-generating techniques for general relativity with a conformally (and minimally) coupled scalar field are pushed forward to build a wide class of asymptotically flat, axisymmetric, and stationary spacetimes continuously connected to Kerr spacetime. This family contains, amongst other things, rotating extensions of the Bocharova-Bronnikov-Melnikov-Bekenstein black hole and also its angular and mass multipolar generalizations. The addition of Newman-Unti-Tamburino charge is also discussed.

We study $D$-dimensional charged static spherically symmetric black hole solutions in Gauss-Bonnet theory coupled to nonlinear electrodynamics defined as arbitrary functions of the field invariant and constrained by several physical conditions. These solutions are characterized in terms of the mass parameter $m$, the electromagnetic energy $ϵ$, and the Gauss-Bonnet parameter $l_{\alpha }^2$. We find that a general feature of these solutions is that the metric behaves in a different way in $D=5$ and $D>5$ space-time dimensions. Moreover, such solutions split into two classes, according to whether they are defined everywhere or they show branch singularities, depending on ($m,ϵ,l_{\alpha }^2$). We describe qualitatively the structures composed in this scenario, which largely extends the results obtained in the literature for several particular families of nonlinear electrodynamics. An explicit new example, illustrative of our results, is introduced. Finally we allow nonvanishing values of the cosmological constant length $l_{\mathrm{\Lambda }}^2$ and study the existence of new structures, in both asymptotically anti–de Sitter and de Sitter spaces.

We investigate the effect of averaging inhomogeneities on expansion and large-scale structure growth observables using the exact and covariant framework of macroscopic gravity (MG). It is well known that applying the Einstein’s equations and spatial averaging do not commute and lead to the averaging problem and backreaction terms. For the MG formalism applied to the Friedman-Lemaitre-Robertson-Walker (FLRW) metric, the extra term can be encapsulated as an averaging density parameter denoted ${\mathrm{\Omega }}_{\mathcal{A}}$. An exact isotropic cosmological solution of MG for the flat FLRW metric is already known in the literature; we derive here an anisotropic exact solution. Using the isotropic solution, we compare the expansion history to current available data of distances to supernovae, baryon acoustic oscillations, cosmic microwave background last scattering surface data, and Hubble constant measurements, and find $-0.05\le {\mathrm{\Omega }}_{\mathcal{A}}\le 0.07$ (at the 95% confidence level). For the flat metric case this reduces to $-0.03\le {\mathrm{\Omega }}_{\mathcal{A}}\le 0.05$. The positive part of the intervals can be rejected if a mathematical (and physical) prior is taken into account. We also find that the inclusion of this term in the fits can shift the values of the usual cosmological parameters by a few to several percents. Next, we derive an equation for the growth rate of large-scale structure in MG that includes a term due to the averaging and assess its effect on the evolution of the growth compared to that of the Lambda cold dark matter ($\mathrm{\Lambda }\mathrm{CDM}$) concordance model. We find that an ${\mathrm{\Omega }}_{\mathcal{A}}$ term of an amplitude range of [$-0.04,-0.02$] lead to a relative deviation of the growth from that of the $\mathrm{\Lambda }\mathrm{CDM}$ of up to 2%–4% at late times. Thus, the shift in the growth could be of comparable amplitude to that caused by similar changes in cosmological parameters like the dark energy density parameter or its equation of state. The effect could also be comparable in amplitude to some systematic effects considered for future surveys. This indicates that the averaging term and its possible effect need to be tightly constrained in future precision cosmological studies.

The Kantowski-Sachs cosmological model sourced by a Skyrme field and a cosmological constant is considered in the framework of general relativity. Assuming a constant radial profile function $\alpha =\pi /2$ for the hedgehog ansatz, the Skyrme contribution to Einstein equations is shown to be equivalent to an anisotropic fluid. Using dynamical system techniques, a qualitative analysis of the cosmological equations is presented. Physically interesting features of the model such as isotropization, bounce and recollapse are discussed.

We apply the axion-photon conversion mechanism to the 130 GeV $\gamma$-ray line observed by the Fermi satellite. Near the Galactic center, some astrophysical sources and/or particle dark matter can produce energetic axions (or axionlike particles), and the axions convert to $\gamma$ rays in Galactic magnetic fields along their flight to the Earth. Since continuum $\gamma$-ray and antiproton productions are sufficiently suppressed in axion production, the scenario fits the 130 GeV $\gamma$-ray line without conflicting with cosmic ray measurements. We derive the axion production cross section and the decay rate of dark matter to fit the $\gamma$-ray excess as functions of axion parameters. In the scenario, the $\gamma$-ray spatial distributions depend on both the dark matter profile and the magnetic field configuration, which will be tested by future $\gamma$-ray observations, e.g., H.E.S.S. II, CTA, and GAMMA-400. As an illustrative example, we study realistic supersymmetric axion models, and show the favored parameters that nicely fit the $\gamma$-ray excess.

We consider the possibility that dark matter halos are described by the Fermi-Dirac distribution at finite temperature. This is the case if dark matter is a self-gravitating quantum gas made of massive neutrinos at statistical equilibrium. This is also the case if dark matter can be treated as a self-gravitating collisionless gas experiencing Lynden-Bell’s type of violent relaxation. In order to avoid the infinite mass problem and carry out a rigorous stability analysis, we consider the fermionic King model. In this paper, we study the nondegenerate limit leading to the classical King model. This model was initially introduced to describe globular clusters. We propose to apply it also to large dark matter halos where quantum effects are negligible. We determine the caloric curve and study the thermodynamical stability of the different configurations. Equilibrium states exist only above a critical energy $E_c$ in the microcanonical ensemble and only above a critical temperature $T_c$ in the canonical ensemble. For $E<E_c$, the system undergoes a gravothermal catastrophe and, for $T<T_c$, it undergoes an isothermal collapse. We compute the profiles of density, circular velocity, and velocity dispersion. We compare the predictions of the classical King model to the observations of large dark matter halos. Because of collisions and evaporation, the central density increases while the slope of the halo density profile decreases until an instability takes place. We show that large dark matter halos are relatively well described by the King model at, or close to, the point of marginal microcanonical stability. At that point, the King model generates a density profile that can be approximated by the modified Hubble profile. This profile has a flat core and decreases as $r^{-3}$ at large distances, like the observational Burkert profile. Less steep halos are unstable. For large halos, the flat core is due to finite temperature effects, not to quantum mechanics. We argue that statistical mechanics may provide a good description of dark matter halos. We interpret the discrepancies as a result of incomplete relaxation like in the case of stellar systems.

Many different forms of the de Sitter metric in different coordinate systems are used in the general relativity literature. Two of them are the most common: the static form and the cosmological (exponentially expanding) form. The staticity and nonstationarity of these two different forms are traced back to the noncomoving and comoving nature of the corresponding coordinate systems. In this paper, using the quasi-Maxwell form of the Einstein field equations and a definition of static spacetimes based upon them, we look at these two different forms of the same solution from a new perspective which classifies them as a special case in a general one-parameter family of solutions. Specifically it is proved that, irrespective of the spacetime symmetry, a one-element perfect fluid in any frame noncomoving with the fluid could be the source of a static spacetime, only if its equation of state is that of a dark fluid, namely, $p=-\rho =\text{const}$. These static solutions, which include the well-known de Sitter spacetime, are called de Sitter-type spacetimes. To answer the question posed in the title, we consider static axially and cylindrically symmetric de Sitter-type spacetimes and their dynamic (cosmological) versions. It is shown how despite the seemingly natural expectation based on the presence of $\mathrm{\Lambda }$ as their only parameter, the nonspherical expansions of these genuinely different solutions should be expected indeed. To the best of our knowledge the dynamic version of the cylindrically symmetric de Sitter-type spacetime is introduced here for the first time. Finally it is noted that the identification of the geometric term $\mathrm{\Lambda }{g}_{ij}$ with a perfect fluid with equation of state $p=-\rho =\text{const}$, although mathematically consistent, obscures the crucial role of the (dark) fluid’s velocity in defining a preferred (comoving) coordinate system in de Sitter-type spacetimes.

We consider a class of fermionic dark matter candidates that are charged under both the $\mathrm{SU}(2{)}_L$ and $\mathrm{U}(1{)}_Y$ gauge interactions. In this case a certain amount of dark matter-Higgs couplings, which can split the dark matter into a pair of Majorana fermions, should be present to evade the constraints from the dark matter direct detection experiments. These effects may be probed by means of the dark matter-nucleus scattering via the Higgs-boson exchange process, as well as the electric dipole moments induced by the dark matter and its $\mathrm{SU}(2{)}_L$ partner fields. In this article, we evaluate them with an effective field approach. It turns out that the constraints coming from the experiments for the quantities have already restricted the dark matter with hypercharge $Y\ge 3/2$. Future experiments have sensitivities to probe this class of dark matter candidates, and may disfavor the $Y\ge 1$ cases if no signal is observed. In this case, only the $Y=0$ and $1/2$ cases may be the remaining possibilities for the $\mathrm{SU}(2{)}_L$ charged fermionic dark matter candidates.

We study a scenario in which the dilaton, a pseudo-Goldstone boson of the spontaneous breaking of conformal symmetry, provides a portal between dark matter and the visible sector. We consider the low-energy description of the theory in which the dilaton mixes with the Standard Model Higgs boson, thereby predicting a second scalar at or above the weak scale. We derive the collider and dark matter constraints on the corresponding parameter space and find that existing experimental data point towards the decoupling limit in which the conformal symmetry scale is well above the electroweak scale. Moreover, the thermal production of dark matter implies its mass is likely above the TeV scale. Upcoming direct-detection experiments may allow for the discovery of the dilaton-mediated thermal dark matter while future collider studies will also be sensitive to the available parameter space.

In this work, we sift a simple supersymmetric framework of late invisible decays to and of the gravitino. We study a simple extension of the minimal supersymmetric standard model that includes isosinglet color-triplet superfields and a singlet superfield. We investigate two cases where the gravitino is the lightest supersymmetric particle or the next-to-lightest supersymmetric particle. The next-to-lightest supersymmetric particle decays into two dark matter candidates and has a long lifetime due to gravitationally suppressed interactions. However, because of the absence of any hadronic or electromagnetic products, it satisfies the tight bounds set by big bang nucleosynthesis and the cosmic microwave background. One or both of the dark matter candidates produced in invisible decays can contribute to the amount of dark radiation and suppress perturbations at scales that are being probed by the galaxy power spectrum and the Lyman-alpha forest data. We show that these constraints are satisfied in large regions of the parameter space and, as a result, the late invisible decays to and of the gravitino can be responsible for the entire dark matter relic abundance.

We present theoretical predictions in the framework of the ANP model for single pion production (${\pi }^{+},{\pi }^0$) in ${\nu }_{\mu }$ and ${\overline{\nu }}_{\mu }$ scattering off mineral oil and plastic. Our results for the integrated cross sections and flux-averaged differential distributions are compared to all available data of the MiniBooNE and $\mathrm{MINER}\nu \mathrm{A}$ experiments. While our predictions slightly undershoot the MiniBooNE data, they reproduce the normalization of the $\mathrm{MINER}\nu \mathrm{A}$ data for the kinetic energy distribution. For the dependence on the polar angle, we reproduce the shape of the arbitrarily normalized data.

We report on the results of a search for a Weakly Interacting Massive Particle (WIMP) signal in low-energy data of the Cryogenic Dark Matter Search experiment using a maximum likelihood analysis. A background model is constructed using geant4 to simulate the surface-event background from ${}^{210}\mathrm{Pb}$ decay-chain events, while using independent calibration data to model the gamma background. Fitting this background model to the data results in no statistically significant WIMP component. In addition, we perform fits using an analytic ad hoc background model proposed by Collar and Fields, who claimed to find a large excess of signal-like events in our data. We confirm the strong preference for a signal hypothesis in their analysis under these assumptions, but excesses are observed in both single- and multiple-scatter events, which implies the signal is not caused by WIMPs, but rather reflects the inadequacy of their background model.

We consider the coordinate-space matrix elements that correspond to fixed-angle scattering amplitudes involving partons and Wilson lines in coordinate space, working in Feynman gauge. In coordinate space, both collinear and short-distance limits produce ultraviolet divergences. We classify singularities in coordinate space, and identify neighborhoods associated unambiguously with individual subspaces (pinch surfaces) where the integrals are singular. The set of such regions is finite for any diagram. Within each of these regions, coordinate-space soft-collinear and hard-collinear approximations reproduce singular behavior. Based on this classification of regions and approximations, we develop a series of nested subtraction approximations by analogy to the formalism in momentum space. This enables us to rewrite each amplitude as a sum of terms to which gauge-theory Ward identities can be applied, factorizing them into hard, jet and soft factors, and to confirm the multiplicative renormalizability of products of lightlike Wilson lines. We study in some detail the simplest case, the color-singlet cusp linking two Wilson lines, and show that the logarithm of this amplitude, which is a sum of diagrams known as webs, is closely related to the corresponding subtracted amplitude order by order in perturbation theory. This enables us to confirm that the logarithm of the cusp can be written as the integral of an ultraviolet-finite function over a surface. We study to what extent this result generalizes to amplitudes involving multiple Wilson lines.