At leading twist the transverse momentum dependent parton distributions of the pion consist of two functions, the unpolarized $f_{1,\pi }(x,{\mathit{k}}_{\perp }^2)$ and the Boer-Mulders function $h_{1,\pi }^{\perp }(x,{\mathit{k}}_{\perp }^2)$. We study both functions within a light-front constituent model of the pion, comparing the results with different pion models and the corresponding nucleon distributions from a light-front constituent model. After evolution from the model scale to the relevant experimental scales, the results for the collinear pion valence parton distribution function $f_{1,\pi }(x)$ are in very good agreement with available parametrizations. Using the light-front constituent model results for the Boer-Mulders functions of the pion and nucleon, we calculate the coefficient $\nu$ in the angular distribution of Drell-Yan dileptons produced in pion-nucleus scattering, which is responsible for the violation of the Lam-Tung relation. We find a good agreement with the data, and carefully discuss the range of applicability of our approach.

Metastable excited states ${{}^{3}P}_2,{{}^{3}P}_0$ of heavy alkaline earth atoms of even isotopes are studied for parity violating (PV) effects in radiative emission of neutrino pair (RENP). PV terms arise from interference between two diagrams containing neutrino pair emission of valence spin current and nuclear electroweak charge density proportional to the number of neutrons in nucleus. This mechanism gives large PV effects, since it does not suffer from the suppression of $1/(\text{electron}\text{mass})$ usually present for nonrelativistic atomic electrons. A controllable magnetic field is crucial to identify RENP process by measuring PV observables. Results of PV asymmetries under the magnetic field reversal and the photon circular polarization reversal are presented for an example of Yb atom.

The implications of a large value of the effective Majorana neutrino mass for a class of two texture zero neutrino mass matrices have been studied in the flavor basis. It is found that these textures predict a near maximal atmospheric neutrino mixing angle in the limit of a large effective Majorana neutrino mass. It is noted that this prediction is independent of the values of solar and reactor neutrino mixing angles. We present the symmetry realization of these textures using the discrete cyclic group $Z_3$. It is found that the texture zeros realized in this work remain stable under renormalization group running of the neutrino mass matrix from the seesaw scale to the electroweak scale, at one-loop level.

At measurements of the spectra of intense gamma radiation produced by ultrarelativistic electrons in periodic structures, pileup of arrivals to the detector of several photons from one electron can cause significant deviations of the measured spectrum from the classically evaluated one. The description of experiments then requires summation of all multiphoton contributions. We describe the corresponding resummation procedure for the photon spectral intensity, as well as for the photon multiplicity spectrum, and apply it to the study of radiation spectra with a mix of coherent and incoherent contributions. The impact of multiphoton effects on the radiation spectrum shape is investigated. The limit of high photon multiplicity for the coherent part of the radiation is explored in detail. A method for reconstruction of the underlying single-photon spectrum from the multiphoton one is formulated.

Using the full CDF Run II data sample, we report evidence for a new resonance, which we refer to as $B(5970)$, found simultaneously in the $B^0{\pi }^{+}$ and $B^{+}{\pi }^{-}$ mass distributions with a significance of 4.4 standard deviations. We further report the first study of resonances consistent with orbitally excited $B^{+}$ mesons and an updated measurement of the properties of orbitally excited $B^0$ and $B_s^0$ mesons. We measure the masses and widths of all states, as well as the relative production rates of the $B_1$, $B_2^{*}$, and $B(5970)$ states and the branching fraction of the $B_{s2}^{*0}$ state to either $B^{*+}{K}^{-}$ and $B^{+}{K}^{-}$. Furthermore, we measure the production rates of the orbitally excited $B^{0,+}$ states relative to the $B^{0,+}$ ground state. The masses of the new $B(5970)$ resonances are $5978\pm 5(\text{stat})\pm 12(\text{syst})\mathrm{MeV}/c^2$ for the neutral state and $5961\pm 5(\text{stat})\pm 12(\text{syst})\mathrm{MeV}/c^2$ for the charged state, assuming that the resonance decays into $B\pi$ final states. The properties of the orbitally excited and the new $B(5970{)}^{0,+}$ states are compatible with isospin symmetry.

The supermassive black hole candidates at the center of every normal galaxy might be wormholes created in the early Universe and connecting either two different regions of our Universe or two different universes in a multiverse model. Indeed, the origin of these supermassive objects is not well understood; topological nontrivial structures like wormholes are allowed both in general relativity and in alternative theories of gravity, and current observations cannot rule out such a possibility. In a few years, the VLTI instrument GRAVITY will have the capability to image blobs of plasma orbiting near the innermost stable circular orbit of ${\mathrm{SgrA}}^{*}$, the supermassive black hole candidate in the Milky Way. The secondary image of a hot spot orbiting around a wormhole is substantially different from that of a hot spot around a black hole, because the photon capture sphere of the wormhole is much smaller. The radius of the photon capture sphere is independent of the hot spot model, and therefore its possible detection, which is observationally challenging but not out of reach, can unambiguously test if the center of our Galaxy harbors a wormhole rather than a black hole.

Nonlocal massive gravity can provide an interesting explanation for the late-time cosmic acceleration, with a dark energy equation of state $w_{\mathrm{DE}}$ smaller than $-1$ in the past. We derive the equations of linear cosmological perturbations to confront such models with the observations of large-scale structures. The effective gravitational coupling to nonrelativistic matter associated with galaxy clusterings is close to Newton’s gravitational constant $G$ for a mass scale $m$ slightly smaller than today’s Hubble parameter $H_0$. Taking into account the background expansion history as well as the evolution of matter perturbations ${\delta }_m$, we test for these models with Type Ia Supernovae (SnIa) from Union 2.1, the cosmic microwave background (CMB) measurements from Planck, a collection of baryon acoustic oscillations (BAO), and the growth rate data of ${\delta }_m$. Using a higher value of $H_0$ derived from its direct measurement ($H_0\gtrsim 70\mathrm{km}{\mathrm{s}}^{-1}{\mathrm{Mpc}}^{-1}$) the data strongly support the nonlocal massive gravity model ($-1.1\lesssim w_{\mathrm{DE}}\lesssim -1.04$ in the past) over the $\mathrm{\Lambda }\mathrm{CDM}$ model ($w_{\mathrm{DE}}=-1$), whereas for a lower prior ($67\mathrm{km}{\mathrm{s}}^{-1}{\mathrm{Mpc}}^{-1}\lesssim H_0\lesssim 70\mathrm{km}{\mathrm{s}}^{-1}{\mathrm{Mpc}}^{-1}$) the two models are statistically comparable.

Group field theories (GFT) are higher dimensional generalizations of matrix models whose Feynman diagrams are dual to triangulations. Here we propose a modification of GFT models that includes extra field indices keeping track of the bubbles of the graphs in the Feynman evaluations. In dimension three, our model exhibits new symmetries, interpreted as the action of the vertex translations of the triangulation. The extra field indices have an elegant algebraic interpretation: they encode the structure of a semisimple algebra. Remarkably, when the algebra is chosen to be associative, the new structure contributes a topological invariant from each bubble of the graph to the Feynman amplitudes.

High-order terms in the post-Newtonian (PN) expansions of various quantities for compact binaries exhibit a combinatorial increase in complexity, with an ever-increasing number of terms, including more transcendentals and logarithms of the velocity, higher powers of these transcendentals and logarithms, and larger and larger rational numbers as coefficients. Here we consider the gravitational wave energy flux at infinity from a point particle in a circular orbit around a Schwarzschild black hole, which is known to 22PN [$O(v^{44})$, where $v$ is the particle’s orbital velocity] beyond the lowest-order Newtonian prediction, at which point each order has over 1000 terms. We introduce a factorization that considerably simplifies the spherical harmonic modes of the energy flux (and thus also the amplitudes of the spherical harmonic modes of the gravitational waves); it is likely that much of the complexity this factorization removes is due to wave propagation on the Schwarzschild spacetime (e.g., tail effects). For the modes with azimuthal number $\ell \ge 7$, this factorization reduces the expressions for the modes that enter the 22PN total energy flux to pure integer PN series with rational coefficients, which amounts to a reduction of up to a factor of $\sim 150$ in the total number of terms in a given mode (and also in the size of the entire expression for the mode). The reduction in complexity becomes less dramatic for smaller $\ell$, due to the structure of the expansion, and one only obtains purely rational coefficients up to some order, though the factorization is still able to remove all the half-integer PN terms. For the 22PN $\ell =2$ modes, this factorization still reduces the total number of terms (and size) by a factor of $\sim 10$ and gives purely rational coefficients through 8PN. This factorization also improves the convergence of the series, though we find the exponential resummation introduced for the full energy flux in [Isoyama et al., Phys. Rev. D 87, 024010 (2013)] to be even more effective at improving the convergence of the individual modes, producing improvements of over 4 orders of magnitude over the original series for some modes. However, the exponential resummation is not as effective at simplifying the series, particularly for the higher-order modes.

Galaxy clusters can efficiently convert axionlike particles (ALPs) to photons. We propose that the recently claimed detection of a 3.55–3.57 keV line in the stacked spectra of a large number of galaxy clusters and the Andromeda galaxy may originate from the decay of either a scalar or fermionic 7.1 keV dark matter species into an ALP of mass $m_a\lesssim 6\times 10^{-11}\mathrm{eV}$, which subsequently converts to a photon in the cluster magnetic field. In contrast to models in which the photon line arises directly from dark matter decay or annihilation, this can explain the anomalous line strength in the Perseus cluster. As cool-core clusters have high central magnetic fields and axion-photon conversion scales as $B^2$, this model can also explain the observed peaking of the line emission in the cool cores of the Perseus, Ophiuchus, and Centaurus clusters, as opposed to the much larger dark matter halos. We describe distinctive predictions of this scenario for future observations.

We present a calculation using lattice QCD of the ratios of decay constants of the excited states of the pion, to that of the pion ground state, at three values of the pion mass between 400 and 700 MeV, using an anisotropic clover fermion action with three flavors of quarks. We find that the decay constant of the first excitation, and more notably of the second, is suppressed with respect to that of the ground-state pion, but that the suppression shows little dependence on the quark mass. The strong suppression of the decay constant of the second excited state is consistent with its interpretation as a predominantly hybrid state.

In this work corrections to low energy punctual effective quark couplings up to the eighth order are calculated by considering vacuum polarization effects with the scalar quark-antiquark condensate. The departing point is a QCD-based Nambu–Jona-Lasinio model. By separating the quark field into two components, one that condenses and another one for interacting quarks, the former is integrated out with the help of usual auxiliary fields and an effective action in terms of interacting quark fields is found. The scalar auxiliary field reduces to the quark-antiquark condensate in the vacuum and the determinant is expanded in powers of the quark-antiquark bilinears generating chiral invariant effective 2N-quark interactions ($N=2,3\dots$). The corresponding coupling constants and effective masses are estimated, and the general trend is that for increasing the effective gluon mass the values of the effective coupling constants decrease. All the values are in good agreement with phenomenological fits.

Recently the CDMS collaboration has reported an excess of events in the signal region of a search for dark matter scattering with Silicon nuclei [R. Agnese et al. (CDMS Collaboration), Phys. Rev. Lett. 111, 251301 (2013)]. Three events on an expected background of 0.4 have a significance of about $2\sigma$, and it is premature to conclude that this is a signal of dark matter. Nonetheless, it is important to examine the space of particle theories capable of explaining this excess, to see what theories are capable of explaining it, and how one might exclude it or find corroborating evidence in other channels. We examine a simplified model containing a scalar mediator particle and find regions consistent with the CDMS observations. Bounds from colliders put important restrictions on the theory, but viable points, including points leading to the observed thermal relic density, survive.

The surface detector array of the Pierre Auger Observatory provides information about the longitudinal development of the muonic component of extensive air showers. Using the timing information from the flash analog-to-digital converter traces of surface detectors far from the shower core, it is possible to reconstruct a muon production depth distribution. We characterize the goodness of this reconstruction for zenith angles around 60° and different energies of the primary particle. From these distributions, we define $X_{\max }^{\mu }$ as the depth along the shower axis where the production of muons reaches maximum. We explore the potentiality of $X_{\max }^{\mu }$ as a useful observable to infer the mass composition of ultrahigh-energy cosmic rays. Likewise, we assess its ability to constrain hadronic interaction models.

The description of the Zitterbewegung at a classical level indicates possible predictions of the electron quantum properties even before quantization: this quivering motion is restricted to a plane, which leads us to only two possible orientations of the corresponding angular momentum, even in the absence of a quantized theory or external fields. Besides, the angular momentum associated with the Zitterbewegung turns out to be proportional to $\hslash$. Namely, using a standard constraint analysis we have proven this last result. Thus, assuming that this is an observable phenomenon, we recognize this oscillatory motion as a classical signature of the spin of the electron. We also propose here an interpretation of the Zitterbewegung based on geometrical grounds: it can be seen as the physical degrees of freedom of position variables constrained to a sphere, which enforces the hypothesis of assuming an electron internal structure.

We have developed a highly accurate numerical code capable of solving the coupled Einstein-Klein-Gordon system, in order to construct rotating boson stars in general relativity. Free fields and self-interacting fields, with quartic and sextic potentials, are considered. In particular, we present the first numerical solutions of rotating boson stars with rotational quantum number $k=3$ and $k=4$, as well as the first determination of the maximum mass of free-field boson stars with $k=2$. We have also investigated timelike geodesics in the spacetime generated by a rotating boson star for $k=1$, 2 and 3. A numerical integration of the geodesic equation has enabled us to identify a peculiar type of orbit: the zero-angular-momentum ones. These orbits pass very close to the center and are qualitatively different from orbits around a Kerr black hole. Should such orbits be observed, they would put stringent constraints on astrophysical compact objects like the Galactic center.

The building of a time machine, if possible at all, requires the relevant regions of spacetime to be compact (that is, physically speaking, free from sources of unpredictability such as infinities and singularities). Motivated by this argument we consider the spacetimes with the compactly determined Cauchy horizons (CDCHs), the defining property of which is the compactness of $\overline{J^{-}(\mathcal{U})}\cap J^{+}({\mathcal{S}}_0)$, where $\mathcal{U}$ is an open subset of the Cauchy horizon and ${\mathcal{S}}_0$ is a Cauchy surface of the initial globally hyperbolic region $M^{\text{in}}$. The following two facts are established: (1) $M^{\text{in}}$ has no globally hyperbolic maximal extension. This means that, by shaping appropriately a precompact portion of a globally hyperbolic region, one can force the Universe to produce either a closed causal curve, or a quasiregular singularity, whichever it abhors less. (2) Before a CDCH is formed a null geodesic appears which infinitely approaches the horizon returning again and again in the same—arbitrarily small—region. The energy of the photon moving on such a geodesic increases with each passage, or at least falls insufficiently fast. As a result, an observer located in the mentioned region would see a bunch of photons passing through his laboratory with the arbitrarily large total energy. We speculate that this phenomenon may have observable consequences.

Motivated by the properties of matter quantum fields in curved space-times, we work out a gravity theory that combines the Born-Infeld gravity Lagrangian with an $f(R)$ piece. To avoid ghostlike instabilities, the theory is formulated within the Palatini approach. This construction provides more freedom to address a number of important questions, such as the dynamics of the early Universe and the cosmic accelerated expansion, among others. In particular, we consider the effect that adding an $f(R)=a{R}^2$ term has on the early-time cosmology. We find that bouncing solutions are robust against these modifications of the Lagrangian whereas the solutions with loitering behavior of the original Born-Infeld theory are very sensitive to the $R^2$ term. In fact, these solutions are modified in such a way that a plateau in the $H^2$ function may arise, yielding a period of (approximately) de Sitter inflationary expansion. This inflationary behavior may be found even in a radiation-dominated universe.

Detailed measurements of the CMB lensing signal are an important scientific goal of ongoing ground-based CMB polarization experiments, which are mapping the CMB at high resolution over small patches of the sky. In this work we simulate CMB polarization lensing reconstruction for the $EE$ and $EB$ quadratic estimators with current-generation noise levels and resolution, and show that without boundary effects the known and expected zeroth and first order $N^{(0)}$ and $N^{(1)}$ biases provide an adequate model for nonsignal contributions to the lensing power spectrum estimators. Small sky areas present a number of additional challenges for polarization lensing reconstruction, including leakage of $E$ modes into $B$ modes. We show how simple windowed estimators using filtered pure $B$ modes can greatly reduce the mask-induced mean-field lensing signal and reduce variance in the estimators. This provides a simple method (used with recent observations) that gives an alternative to more optimal but expensive inverse-variance filtering.