A degenerate sfermionic particle spectrum can escape constraints from flavor physics, and at the same time evade the limits from the direct searches if the degeneracy extends to the gaugino-Higgsino sector. Inspired by this, we consider a scenario where all the soft terms have an approximately common mass scale at $M_{\mathrm{SUSY}}$, with splittings $\lesssim \mathcal{O}(10\%)$. As a result, the third generation sfermions have large to maximal (left-right) mixing, the same being the case with charginos and some sectors of the neutralino mass matrix. We study this scenario in the light of discovery of the Higgs boson with mass $\sim 125\mathrm{GeV}$. We consider constraints from $B$ physics, the anomalous magnetic moment of the muon and the dark matter relic density. We find that a supersymmetric spectrum as light as 600 GeV could be consistent with all current data and also account for the observed anomalous magnetic moment of the muon within $2\sigma$. The neutralino relic density is generally too small to saturate the measured cold dark matter relic density. Direct detection limits from XENON100 and LUX put severe constraints on this scenario which will be conclusively probed by the XENONnT experiment.

We report the renormalization and mixing constants to one-loop order for the quark and gluon energy-momentum (EM) tensor operators on the lattice. A unique aspect of this mixing calculation is the definition of the glue EM tensor operator. The glue operator is comprised of gauge-field tensors constructed from the overlap Dirac operator. The resulting perturbative calculations are performed using methods similar to the Kawai approach using the Wilson fermion and gauge actions for all QCD vertices and the overlap Dirac operator to define the glue EM tensor. Our results are used to connect the lattice QCD results of quark and glue momenta and angular momenta to the $\overline{\mathrm{MS}}$ scheme at input scale $\mu$.

Flavor-twisted boundary conditions can be used for exponential reduction of finite volume artifacts in flavor-averaged observables in lattice QCD calculations with $SU(N_f)$ light quark flavor symmetry. Finite volume artifact reduction arises from destructive interference effects in a manner closely related to the phase averaging which leads to large $N_{\mathrm{c}}$ volume independence. With a particular choice of flavor-twisted boundary conditions, finite volume artifacts for flavor-singlet observables in a hypercubic spacetime volume are reduced to the size of finite volume artifacts in a spacetime volume with periodic boundary conditions that is four times larger.

The presence of terms that violate quark-hadron duality in the expansion of QCD Green’s functions is a generally accepted fact. Recently, a new approach was proposed for the study of duality violations (DVs), which exploits the existence of a rigorous lower bound on the functional distance, measured in a certain norm, between a “true” correlator and its approximant calculated theoretically along a contour in the complex energy plane. In the present paper, we pursue the investigation of functional-analysis-based tests towards their application to real spectral function data. We derive a closed analytic expression for the minimal functional distance based on the general weighted $L^2$ norm and discuss its relation with the distance measured in the $L^{\infty }$ norm. Using fake data sets obtained from a realistic toy model in which we allow for covariances inspired from the publicly available ALEPH spectral functions, we obtain, by Monte Carlo simulations, the statistical distribution of the strength parameter that measures the magnitude of the DV term added to the usual operator product expansion. The results show that, if the region with large errors near the end point of the spectrum in $\tau$ decays is excluded, the functional-analysis-based tests using either $L^2$ or $L^{\infty }$ norms are able to detect, in a statistically significant way, the presence of DVs in realistic spectral function pseudodata.

We study the production of polarized $\mathrm{\Lambda }$ hyperon in semi-inclusive deep inelastic scattering off an unpolarized target. We include the cases in which the $\mathrm{\Lambda }$ hyperon is longitudinally polarized or transversely polarized, and in which the lepton beam is unpolarized or longitudinally polarized. Within the framework of the transverse momentum dependent factorization, we take into account the complete decomposition of the parton correlator for fragmentation up to twist-3. We present the cross-section of the process to order $1/Q$. The expressions of the polarized structure functions, which may give rise to various spin asymmetries, are also given.

Asymptotic safety provides a mechanism for constructing a consistent and predictive quantum theory of gravity valid on all length scales. Its key ingredient is a non-Gaussian fixed point of the gravitational renormalization group flow which controls the scaling of couplings and correlation functions at high energy. In this work we use a functional renormalization group equation adapted to the Arnowitt-Deser-Misner formalism for evaluating the gravitational renormalization group flow on a cosmological Friedmann-Robertson-Walker background. Besides possessing the non-Gaussian fixed-point characteristic for asymptotic safety the setting exhibits a second family of non-Gaussian fixed points with a positive Newton’s constant and real critical exponents. The presence of these new fixed points alters the phase diagram in such a way that all renormalization group trajectories connected to classical general relativity are well defined on all length scales. In particular a positive cosmological constant is dynamically driven to zero in the deep infrared. Moreover, the scaling dimensions associated with the universality classes emerging within the causal setting exhibit qualitative agreement with results found within the $\epsilon$-expansion around two dimensions, Monte Carlo simulations based on lattice quantum gravity, and the discretized Wheeler-DeWitt equation.

We compute the isotropic gravitational wave (GW) background produced by binary supermassive black holes (SBHs) in galactic nuclei. In our model, massive binaries evolve at early times via gravitational-slingshot interaction with nearby stars, and at later times by the emission of GWs. Our expressions for the rate of binary hardening in the “stellar” regime are taken from the recent work of Vasiliev et al., who show that in the nonaxisymmetric galaxies expected to form via mergers, stars are supplied to the center at high enough rates to ensure binary coalescence on Gyr timescales. We also include, for the first time, the extra degrees of freedom associated with evolution of the binary’s orbital plane; in rotating nuclei, interaction with stars causes the orientation and the eccentricity of a massive binary to change in tandem, leading in some cases to very high eccentricities ($e>0.9$) before the binary enters the GW-dominated regime. We argue that previous studies have over-estimated the mean ratio of SBH mass to galaxy bulge mass by factors of 2–3. In the frequency regime currently accessible to pulsar timing arrays (PTAs), our assumptions imply a factor 2–3 reduction in the characteristic strain compared with the values computed in most recent studies, removing the tension that currently exists between model predictions and the nondetection of GWs.

A class of nonstationary spacetimes is obtained by means of a conformal transformation of the Schwarzschild metric, where the conformal factor $a(t)$ is an arbitrary function of the time coordinate only. We investigate several situations including some where the final state is a central object with constant mass. The metric is such that there is an initial big-bang type singularity and the final state depends on the chosen conformal factor. The Misner-Sharp mass is computed and a localized central object may be identified. The trapping horizons, geodesic and causal structure of the resulting spacetimes are investigated in detail. When $a(t)$ asymptotes to a constant in a short enough time scale, the spacetime presents an event horizon and its analytical extension reveals black-hole or white-hole regions. On the other hand, when $a(t)$ is unbounded from above as in cosmological models, the spacetime presents no event horizons and may present null singularities in the future. The energy-momentum content and other properties of the respective spacetimes are also investigated.

A dark radiation term arises as a correction to the energy-momentum tensor in the simplest five-dimensional RS-II brane-world cosmology. In this paper we revisit the constraints on dark radiation based upon the newest results for light element nuclear reaction rates, observed light element abundances, and the power spectrum of the cosmic microwave background (CMB). Adding dark radiation during big bang nucleosynthesis (BBN) alters the Friedmann expansion rate, causing the nuclear reactions to freeze out at a different temperature. This changes the final light element abundances at the end of BBN. Its main influence on the CMB is to change the effective expansion rate at the surface of last scattering. We find that our adopted BBN constraints reduce the allowed range for dark radiation to between $-12.1\%$ and $+6.2\%$ of the ambient background energy density. Combining this result with fits to the CMB power spectrum, the range decreases to $-6.0\%$ to $+6.2\%$. Thus, we find, that the ratio of brane-world dark radiation to the background total relativistic mass energy density ${\rho }_{\mathrm{DR}}/\rho$ (fixed at 10 MeV) is consistent with zero, although in the BBN analysis there could be a slight preference for a negative contribution. However, the BBN constraint depends strongly upon the adopted primordial helium abundance.

We investigate the behavior of bouncing Bianchi type IX “mixmaster” universes in general relativity. This generalizes all previous studies of the cyclic behavior of closed spatially homogeneous universes with and without an entropy increase. We determine the behavior of models containing radiation by analytic and numerical integration and show that an increase of radiation entropy leads to an increasing cycle size and duration. We introduce a null energy condition violating ghost field to create a smooth, nonsingular bounce of finite size at the end of each cycle and compute the evolution through many cycles with and without an entropy increase injected at the start of each cycle. In the presence of increasing entropy, we find that the cycles grow larger and longer and the dynamics approach flatness, as in the isotropic case. However, successive cycles become increasingly anisotropic at the expansion maxima which is dominated by the general-relativistic effects of anisotropic 3-curvature. When the dynamics are significantly anisotropic, the 3-curvature is negative. However, it becomes positive after continued expansion drives the dynamics close enough to isotropy for the curvature to become positive and for gravitational collapse to ensue. In the presence of a positive cosmological constant, radiation, and a ghost field, we show that, for a very wide range of cosmological constant values, the growing oscillations always cease and the dynamics subsequently approach those of the isotropic de Sitter universe at late times. This model is not included in the scope of earlier cosmic no-hair theorems because the 3-curvature can be positive. In the case of a negative cosmological constant, radiation, and an ultrastiff field (to create nonsingular bounces), we show that a sequence of chaotic oscillations also occurs, with sensitive dependence on initial conditions. In all cases, we follow the oscillatory evolution of the scale factors, the shear, and the 3-curvature from cycle to cycle.

We propose a novel mechanism that explains the cored dark matter density profile in recently observed dark matter rich dwarf spheroidal galaxies. In our scenario, dark matter particle mass decreases gradually as a function of distance towards the center of a dwarf galaxy due to its interaction with a chameleon scalar. At closer distance towards the Galactic center the strength of attractive scalar fifth force becomes much stronger than gravity and is balanced by the Fermi pressure of the dark matter cloud; thus, an equilibrium static configuration of the dark matter halo is obtained. Like the case of soliton star or fermion Q-star, the stability of the dark matter halo is obtained as the scalar achieves a static profile and reaches an asymptotic value away from the Galactic center. For simple scalar-dark matter interaction and quadratic scalar self-interaction potential, we show that dark matter behaves exactly like cold dark matter (CDM) beyond a few kpc away from the Galactic center but at closer distance it becomes lighter and Fermi pressure cannot be ignored anymore. Using Thomas-Fermi approximation, we numerically solve the radial static profile of the scalar field, fermion mass and dark matter energy density as a function of distance. We find that for fifth force mediated by an ultralight scalar, it is possible to obtain a flattened dark matter density profile towards the Galactic center. In our scenario, the fifth force can be neglected at distance $r\ge 1\mathrm{kpc}$ from the Galactic center and dark matter can be simply treated as heavy nonrelativistic particles beyond this distance, thus reproducing the success of CDM at large scales.

In this work we use the newly reported boron-to-carbon ratio (B/C) from AMS-02 and the time-dependent proton fluxes from PAMELA and AMS-02 to constrain the source and propagation parameters of cosmic rays in the Milky Way. A linear correlation of the solar modulation parameter with solar activities is assumed to account for the time-varying cosmic ray fluxes. A comprehensive set of propagation models, with or without reacceleration or convection, has been discussed and compared. We find that only the models with reacceleration can self-consistently fit both the proton and B/C data. The rigidity dependence slope of the diffusion coefficient, $\delta$, is found to be about 0.38–0.50 for the diffusion-reacceleration models. The plain diffusion and diffusion-convection models fit the data poorly. We compare different model predictions of the positron and antiproton fluxes with the data. We find that the diffusion-reacceleration models overproduce low energy positrons, while nonreacceleration models give better fit to the data. As for antiprotons, reacceleration models tend to underpredict low energy antiproton fluxes, unless a phenomenological modification of the velocity dependence of the diffusion coefficient is applied. Our results suggest that there could be important differences of the propagation for nuclei and leptons, in either the Milky Way or the solar heliosphere.

The detection of unmodeled gravitational wave transients (bursts) using a network of interferometric detectors affected by non-Gaussian (glitchy) noise is studied, starting from first principles, for the simplest case where the source position on the celestial sphere is fiducially known from different (e.g., optical, radio, or neutrino) observations. Interferometer noise modelling is preliminarily discussed in an operational perspective. Two alternative, locally optimum detectors are proposed and evaluated in simulated realistic non-Gaussian (glitchy) noise, together with robust implementations which are tolerant against incomplete knowledge or fluctuations of the noise features. These detectors outperform those based on the unrealistic stationary/Gaussian noise assumption, and in principle, do not require preliminary ad hoc data vetoing or laundering. They are structurally akin to those adopted in current data analysis pipelines, preserving their correlation structure, and use simple memoryless nonlinearities for data preprocessing, with only a minor added computational burden.

We describe a directed search for continuous gravitational waves in data from the sixth initial LIGO science run. The target was the nearby globular cluster NGC 6544 at a distance of $\approx 2.7\mathrm{kpc}$. The search covered a broad band of frequencies along with first and second frequency derivatives for a fixed sky position. The search coherently integrated data from the two LIGO interferometers over a time span of 9.2 days using the matched-filtering $\mathcal{F}$-statistic. We found no gravitational-wave signals and set 95% confidence upper limits as stringent as $6.0\times {10}^{-25}$ on intrinsic strain and $8.5\times {10}^{-6}$ on fiducial ellipticity. These values beat the indirect limits from energy conservation for stars with characteristic spin-down ages older than 300 years and are within the range of theoretical predictions for possible neutron-star ellipticities. An important feature of this search was use of a barycentric resampling algorithm which substantially reduced computational cost; this method is used extensively in searches of Advanced LIGO and Virgo detector data.

We show that for values of masses of the gluino and stop favored by “naturalness,” the top quark produced in the decay $\tilde{g}\to t{\tilde{t}}_1$ can be polarized. This polarization depends only on the mixing in the stop sector as opposed to that of the top quark produced in decays $\tilde{t}\to t{\tilde{\chi }}_i^0$, $\tilde{b}\to t{\tilde{\chi }}_i^{-}$. In both the cases the polarization constructed through the distribution of top decay products in the laboratory frame, is different from the top polarization predicted in the rest frame of the mother particle (gluino/stop), which depends on the SUSY parameters as mentioned above. Here, we propose an estimator of lab frame top quark polarization, starting from the rest frame polarization of the top. This estimator depends only on the magnitude of velocity of the mother particle and assumes a narrow width for the mother particle. With a Monte-Carlo simulation of the full production and decay chain we establish our estimator to be accurate within 1% and the computation is a much simpler exercise compared to calculating from first principle. We also study effects of finite width of the mother particle using a suitably modified estimator and find it most useful for stop-quarks decays.

We compute the masses of even spin glueball states $J^{PC}$, with $P=C=+1$, using a twist two operator from an AdS/QCD model known as the hardwall model, using Dirichlet and Neumann boundary conditions. Within this approach, we found that the glueball masses are comparable with those in literature. From these masses, we obtained the Pomeron Regge trajectories for both boundary conditions in agreement with experimental data available and other holographic models.

We present a derivation of coherent helicity amplitudes for a particle decaying into multifinal states with nonzero spins. The results show that the coherent amplitudes introduce additional rotations to transform the helicities into a consistent helicity system, which allows us to add helicity amplitudes for different decay chains coherently. These rotations may have significant effects on the interference between the decay chains in the partial wave analysis.

A multiplicity of quark-lepton families can naturally arise as zero modes in flux compactifications. The flavor structure of quark and lepton mass matrices is then determined by the wave function profiles of the zero modes. We consider a supersymmetric $SO(10)\times U(1)$ model in six dimensions compactified on the orbifold $T^2/{\mathbb{Z}}_2$ with Abelian magnetic flux. A bulk $\mathbf{16}$-plet charged under the $U(1)$ provides the quark-lepton generations whereas two uncharged $\mathbf{10}$-plets yield two Higgs doublets. Bulk anomaly cancellation requires the presence of additional $\mathbf{16}$- and $\mathbf{10}$-plets. The corresponding zero modes form vectorlike split multiplets that are needed to obtain a successful flavor phenomenology. We analyze the pattern of flavor mixings for the two heaviest families of the Standard Model and discuss possible generalizations to three and more generations.

We discuss weak kaon decays in a scenario in which the Standard Model is extended by massive sterile fermions. After revisiting the analytical expressions for leptonic and semileptonic decays we derive the expressions for decay rates with two neutrinos in the final state. By using a simple effective model with only one sterile neutrino, compatible with all current experimental bounds and general theoretical constraints, we conduct a thorough numerical analysis which reveals that the impact of the presence of massive sterile neutrinos on kaon weak decays is very small, less than 1% on decay rates. The only exception is $\mathcal{B}(K_L\to \nu \nu )$, which can go up to $\mathcal{O}({10}^{-10})$, thus possibly within the reach of the KOTO, NA62 and SHIP experiments. Plans have also been proposed to search for this decay at the NA64 experiment. In other words, if all the future measurements of weak kaon decays turn out to be compatible with the Standard Model predictions, this will not rule out the existence of massive light sterile neutrinos with non-negligible active-sterile mixing. Instead, for a sterile neutrino of mass below $m_K$, one might obtain a huge enhancement of $\mathcal{B}(K_L\to \nu \nu )$, otherwise negligibly small in the Standard Model.

The transition form factor of a gamma into three pions $F_{3\pi }$ is studied in a framework of nonlocal chiral quark model. In the local limit the result is in agreement with chiral perturbative theory and reproduce Wess-Zumino-Witten anomaly. Nonlocality does not change the value of transition form factor in chiral limit. On the physical threshold of reaction the form factor $F_{3\pi }$ obtained is in a good agreement with experimental data if the current quark mass is taken into account in the model.