The answer is yes. We indeed find that interacting dark energy can alleviate the current tension on the value of the Hubble constant $H_0$ between the cosmic microwave background anisotropies constraints obtained from the Planck satellite and the recent direct measurements reported by Riess et al. 2016. The combination of these two data sets points toward a nonzero dark matter-dark energy coupling $\xi$ at more than two standard deviations, with $\xi =-0.26_{-0.12}^{+0.16}$ at 95% C.L., i.e. with a moderate evidence for interacting dark energy with an odds ratio of $6:1$ respect to a non interacting cosmological constant. However the $H_0$ tension is better solved when the equation of state of the interacting dark energy component is allowed to freely vary, with a phantomlike equation of state $w=-1.185\pm 0.064$ (at 68% C.L.), ruling out the pure cosmological constant case, $w=-1$, again at more than two standard deviations. When Planck data are combined with external datasets, as BAO, JLA Supernovae Ia luminosity distances, cosmic shear or lensing data, we find perfect consistency with the cosmological constant scenario and no compelling evidence for a dark matter-dark energy coupling.

Determining the differential-rotation law of compact stellar objects produced in binary neutron stars mergers or core-collapse supernovae is an old problem in relativistic astrophysics. Addressing this problem is important because it impacts directly on the maximum mass these objects can attain and, hence, on the threshold to black-hole formation under realistic conditions. Using the results from a large number of numerical simulations in full general relativity of binary neutron star mergers described with various equations of state and masses, we study the rotational properties of the resulting hypermassive neutron stars. We find that the angular-velocity distribution shows only a modest dependence on the equation of state, thus exhibiting the traits of “quasiuniversality” found in other aspects of compact stars, both isolated and in binary systems. The distributions are characterized by an almost uniformly rotating core and a “disk.” Such a configuration is significantly different from the $j$-constant differential-rotation law that is commonly adopted in equilibrium models of differentially rotating stars. Furthermore, the rest-mass contained in such a disk can be quite large, ranging from $\simeq 0.03M_{\odot }$ in the case of high-mass binaries with stiff equations of state, up to $\simeq 0.2M_{\odot }$ for low-mass binaries with soft equations of state. We comment on the astrophysical implications of our findings and on the long-term evolutionary scenarios that can be conjectured on the basis of our simulations.

We consider propagation of high-energy earth-skimming taus produced in interactions of astrophysical tau neutrinos. For astrophysical tau neutrinos, we take generic power-law flux, $E^{-2}$ and the cosmogenic flux initiated by the protons. We calculate tau energy loss in several approaches, such as dipole models and the phenomenological approach in which parametrization of the $F_2$ is used. We evaluate the tau neutrino charged-current cross section using the same approaches for consistency. We find that uncertainty in the neutrino cross section and in the tau energy loss partially compensate giving very small theoretical uncertainty in the emerging tau flux for distances ranging from 2 to 100 km and for the energy range between $10^6$ and $10^{11}\mathrm{GeV}$, focusing on energies above $10^8\mathrm{GeV}$. When we consider uncertainties in the neutrino cross section, inelasticity in neutrino interactions and the tau energy loss, which are not correlated, i.e. they are not all calculated in the same approach, theoretical uncertainty ranges from about 30% and 60% at $10^8\mathrm{GeV}$ to about factors of 3.3 and 3.8 at $10^{11}\mathrm{GeV}$ for the $E^{-2}$ flux and the cosmogenic flux, respectively, for the distance of 10 km rock. The spread in predictions significantly increases for much larger distances, e.g., $\sim 1,000\mathrm{km}$. Most of the uncertainty comes from the treatment of photonuclear interactions of the tau in transit through large distances. We also consider Monte Carlo calculation of the tau propagation and we find that the result for the emerging tau flux is in agreement with the result obtained using analytic approach. Our results are relevant to several experiments that are looking for skimming astrophysical taus, such as the Pierre Auger Observatory, HAWC and Ashra. We evaluate the aperture for the Auger and discuss briefly application to the other two experiments.

Measurements of the ratio of $B\to K^{*}\mu \mu$ to $B\to K^{*}ee$ branching fractions, $R_{K^{*}}$, by the LHCb Collaboration strengthen the hints from previous studies with pseudoscalar kaons, $R_K$, for the breakdown of lepton universality, and therefore the Standard Model (SM), to $\sim 3.5\sigma$. Complementarity between $R_K$ and $R_{K^{*}}$ allows us to pin down the Dirac structure of the new contributions to be predominantly SM-like chiral, with possible admixture of chirality-flipped contributions of up to $\mathcal{O}(\mathrm{few}10\%)$. Scalar and vector leptoquark representations $(S_3,V_1,V_3)$ plus possible (${\tilde{S}}_2,V_2$) admixture can explain $R_{K,K^{*}}$ via tree-level exchange. Flavor models naturally predict leptoquark masses not exceeding a few TeV, with couplings to third-generation quarks at $O(0.1)$, implying that this scenario can be directly tested at the LHC.

We study a lattice model comprising four massless reduced staggered fermions in four dimensions coupled through an $SU(4)$-invariant four-fermion interaction. We present both theoretical arguments and numerical evidence that no bilinear fermion condensates are present for any value of the four-fermi coupling, in contrast to earlier studies of Higgs-Yukawa models with different exact lattice symmetries. At strong coupling we observe the formation of a four-fermion condensate and a mass gap in spite of the absence of bilinear condensates. Unlike those previously studied systems we do not find a ferromagnetic phase separating this strong-coupling phase from the massless weak-coupling phase. Instead we observe long-range correlations in a narrow region of the coupling, still with vanishing bilinear condensates. While our numerical results come from relatively small lattice volumes that call for caution in drawing conclusions, if this novel phase structure is verified by future investigations employing larger volumes it may offer the possibility for new continuum limits for strongly interacting fermions in four dimensions.

We critically reconsider the Landau-Ginzburg-Wilson (LGW) approach to critical phenomena in the presence of gauge symmetries. In the LGW framework, to obtain the universal features of a continuous transition, one identifies the order parameter $\mathrm{\Phi }$ and considers the corresponding most general ${\mathrm{\Phi }}^4$ field theory that has the same symmetries as the original model. In the presence of gauge symmetries, one usually considers a gauge-invariant order parameter and a LGW field theory that is invariant under the global symmetries of the original model. We show that this approach, in which the gauge dynamics is effectively integrated out, may sometimes lead to erroneous conclusions on the nature of the critical behavior. As an explicit example, we show that the above-described LGW approach generally fails for the three-dimensional ferromagnetic and antiferromagnetic ${\mathrm{CP}}^{N-1}$ models, which are invariant under global $\mathrm{U}(N)$ and local U(1) transformations. We point out possible implications for the finite-temperature chiral transition of nuclear matter.

In this work we present the results of our investigation of SU(2) gauge theory with two Dirac fermions in the adjoint representation (aQCD2), which belongs to the class of strongly interacting gauge theories that are of basic interest for extensions of the Standard Model. We have done numerical lattice simulations of this theory at two different values of the gauge coupling and several fermion masses. Our results include the particle spectrum and the mass anomalous dimension. The spectrum contains new exotic fermion-gluon states and flavor-singlet mesons. The mass anomalous dimension is determined from the scaling of the masses and the mode number. The remnant dependence of the universal mass ratios and mass anomalous dimension on the gauge coupling indicates the relevance of scaling corrections, such that earlier estimations for the universal fixed point value of the mass anomalous dimension are incomplete without their inclusion.

We study the bulk viscosity of quark matter in the strong coupling regime within the two-flavor Nambu–Jona-Lasinio model. The dispersive effects that lead to nonzero bulk viscosity arise from quark-meson fluctuations above the Mott transition temperature, where meson decay into two quarks is kinematically allowed. We adopt the Kubo-Zubarev formalism and compute the equilibrium imaginary-time correlation function for pressure in the $O(1/N_c)$ power counting scheme. The bulk viscosity of matter is expressed in terms of the Lorentz components of the quark spectral function and includes multiloop contributions which arise via resummation of infinite geometrical series of loop diagrams. We show that the multiloop contributions dominate the single-loop contribution close to the Mott line, whereas at high temperatures the one-loop contribution is dominant. The multiloop bulk viscosity dominates the shear viscosity close to the Mott temperature by factors 5 to 20, but, with increasing temperature, the shear viscosity becomes the dominant dissipation mechanism of stresses as the one-loop contribution becomes the main source of bulk viscosity.

We describe dynamical symmetry breaking in a system of massless Dirac fermions with both electromagnetic and four-fermion interactions in ($2+1$) dimensions. The former is described by the pseudo quantum electrodynamics, and the latter is given by the so-called Gross-Neveu action. We apply the Hubbard-Stratonovich transformation and the large-$N_f$ expansion in our model to obtain a Yukawa action. Thereafter, the presence of a symmetry broken phase is inferred from the nonperturbative Schwinger-Dyson equation for the electron propagator. This is the physical solution whenever the fine-structure constant is larger than a critical value ${\alpha }_c(D{N}_f)$. In particular, we obtain the critical coupling constant ${\alpha }_c\approx 0.36$ for $D{N}_f=8$., where $D=2$, 4 corresponds to the SU(2) and SU(4) cases, respectively, and $N_f$ is the flavor number. Our results show a decreasing of the critical coupling constant in comparison with the case of pure electromagnetic interaction, thus yielding a more favorable scenario for the occurrence of dynamical symmetry breaking. Nevertheless, the number of renormalized masses is not changed by the four-fermion interaction within our approximation. For two-dimensional materials, in application in condensed matter systems, it implies an energy gap at the Dirac points or valleys of the honeycomb lattice.

The meson static properties are investigated in a Pauli-Villars regularized Nambu–Jona-Lasinio model in a strong magnetic field. The quark dimension reduction leads to a sudden jump of the mass of the Goldstone mode at the Mott transition temperature. A consequence of such a jump may be some interesting phenomena in relativistic heavy ion collisions, where the strong magnetic field can be created. For instance, when the formed fireball cools down, there might be a sudden enhancement of neutral pions at the Mott transition temperature.

We construct a model where the smallness of the masses of first quark generations implies the near block diagonal nature of the Cabibbo-Kobayashi-Maskawa matrix and vice versa. For this setup, we rely on a two Higgs-doublet model structure with an $S_3$ symmetry. We show that an SM-like Higgs emerges naturally from such a construction. Moreover, the ratio of two VEVs, $\tan \beta$, can be precisely determined from the requirement of the near masslessness of the up- and down-quarks. The flavor changing neutral current structure that arises from our model is also very predictive.

We consider two solutions of Einstein-$\mathrm{\Lambda }$ theory which admit the extremal vanishing horizon (EVH) limit, odd-dimensional multispinning Kerr black hole (in the presence of cosmological constant) and cosmological soliton. We show that the near horizon EVH geometry of Kerr has a three-dimensional maximally symmetric subspace whose curvature depends on rotational parameters and the cosmological constant. In the Kerr-dS case, this subspace interpolates between ${\mathrm{AdS}}_3$, three-dimensional flat and ${\mathrm{dS}}_3$ by varying rotational parameters, while the near horizon of the EVH cosmological soliton always has a ${\mathrm{dS}}_3$. The feature of the EVH cosmological soliton is that it is regular everywhere on the horizon. In the near EVH case, these three-dimensional parts turn into the corresponding locally maximally symmetric spacetimes with a horizon: Kerr-${\mathrm{dS}}_3$, flat space cosmology or BTZ black hole. We show that their thermodynamics match with the thermodynamics of the original near EVH black holes. We also briefly discuss the holographic two-dimensional CFT dual to the near horizon of EVH solutions.

We explore an extended cosmological scenario where the dark matter is an admixture of cold and additional noncold species. The mass and temperature of the noncold dark matter particles are extracted from a number of cosmological measurements. Among others, we consider tomographic weak lensing data and Milky Way dwarf satellite galaxy counts. We also study the potential of these scenarios in alleviating the existing tensions between local measurements and cosmic microwave background (CMB) estimates of the $S_8$ parameter, with $S_8={\sigma }_8\sqrt{{\mathrm{\Omega }}_m}$, and of the Hubble constant $H_0$. In principle, a subdominant, noncold dark matter particle with a mass $m_X\sim \mathrm{keV}$, could achieve the goals above. However, the preferred ranges for its temperature and its mass are different when extracted from weak lensing observations and from Milky Way dwarf satellite galaxy counts, since these two measurements require suppressions of the matter power spectrum at different scales. Therefore, solving simultaneously the CMB-weak lensing tensions and the small scale crisis in the standard cold dark matter picture via only one noncold dark matter component seems to be challenging.

We reconsider the possibility that all standard model gauge couplings blow up at a common scale in the ultraviolet. The simplest implementation of this idea assumes supersymmetry and the addition of a single vectorlike generation of matter fields around the TeV scale. We provide an up-to-date numerical study of this scenario and show that either the scale of the additional matter or the scale of the light superparticle masses falls below potentially relevant LHC bounds. We then consider minimal extensions of the extra matter sector that raise its scale above the reach of the LHC, to determine whether there are cases that might be probed at a 100 TeV collider. We also consider the possibility that the heavy matter sector involves new gauge groups constrained by the same ultraviolet boundary condition, which in some cases can provide an explanation for the multiplicity of heavy states. We comment on the relevance of this framework to theories with dark and visible sectors.

We propose a theory in which the Standard Model gauge symmetry is extended by a new $SU(2{)}_{\ell }$ group acting nontrivially on the lepton sector which is spontaneously broken at the TeV scale. Under this $SU(2{)}_{\ell }$ the ordinary leptons form doublets along with new lepton partner fields. This construction naturally contains a dark matter candidate, the partner of the right-handed neutrino, stabilized by a residual global $U(1{)}_{\chi }$ symmetry. We show that one can explain baryogenesis through an asymmetric dark matter scenario, in which generation of related asymmetries in the dark matter and baryon sectors is driven by the $SU(2{)}_{\ell }$ instantons during a first order phase transition in the early Universe.

We present results for the nucleon electromagnetic form factors using an ensemble of maximally twisted mass clover-improved fermions with pion mass of about 130 MeV. We use multiple sink-source separations and three analysis methods to probe ground-state dominance. We evaluate both the connected and disconnected contributions to the nucleon matrix elements. We find that the disconnected quark loop contributions to the isoscalar matrix elements are small, giving an upper bound of up to 2% of the connected and smaller than its statistical error. We present results for the isovector and isoscalar electric and magnetic Sachs form factors and the corresponding proton and neutron form factors. By fitting the momentum dependence of the form factors to a dipole form or to the $z$ expansion, we extract the nucleon electric and magnetic radii, as well as the magnetic moment. We compare our results to experiment as well as to other recent lattice QCD calculations.

We discuss kinetic equations involving the anomalous terms responsible for the chiral anomaly. The general chiral heat wave in cold Fermi liquid is described and the modification of the anomalous zero sound at small temperature and vorticity is found.

We present a compact form of the leptonic currents for the computation of the processes involving an initial virtual boson (photon, $W^{\pm }$, or $Z_0$). For deeply inelastic scattering, once the azimuthal angle of the plane expanded by the initial- and final-state leptons is integrated over in the boson-proton center-of-mass frame, the azimuthal-asymmetric terms vanish, which, however, is not true when some physical quantities (such as the transverse momentum of the observed particle) are specified in the laboratory frame. The misuse of the symmetry may lead to wrong results.

We demonstrate that numerical relativity codes based on the “moving punctures” formalism are capable of evolving nearly maximally spinning black hole binaries. We compare a new evolution of an equal-mass, aligned-spin binary with dimensionless spin $\chi =0.99$ using puncture-based data with recent simulations of the SXS Collaboration. We find that the overlap of our new waveform with the published results of the SXS Collaboration is larger than 0.999. To generate our new waveform, we use the recently introduced HiSpID puncture data, the CCZ4 evolution system, and a modified lapse condition that helps keep the horizon radii reasonably large.