Gravitational waves are excellent tools to probe the foundations of general relativity in the strongly dynamical and nonlinear regime. One such foundation is Lorentz symmetry, which can be broken in the gravitational sector by the existence of a preferred time direction and, thus, a preferred frame at each spacetime point. This leads to a modification in the orbital decay rate of binary systems, and also in the generation and chirping of their associated gravitational waves. Here we study whether waves emitted in the late, quasicircular inspiral of nonspinning, neutron star binaries can place competitive constraints on two proxies of gravitational Lorentz violation: Einstein-Æther theory and khronometric gravity. We model the waves in the small-coupling (or decoupling) limit and in the post-Newtonian approximation, by perturbatively solving the field equations in small deformations from general relativity and in the small-velocity or weak-gravity approximation. We assume that a gravitational wave consistent with general relativity has been detected with second- and third-generation, ground-based detectors, and with the proposed space-based mission DECIGO, with and without coincident electromagnetic counterparts. Without a counterpart, a detection consistent with general relativity can only place competitive constraints on gravitational Lorentz violation when using future, third-generation or space-based instruments. On the other hand, a single counterpart is enough to place constraints that are 10 orders of magnitude more stringent than current binary pulsar bounds, even when using second-generation detectors. This is because Lorentz violation forces the group velocity of gravitational waves to be different from that of light, and this difference can be very accurately constrained with coincident observations.

The purpose of this work is to understand the relation between the trivial vacuum in light-front field theory and the nontrivial vacuum in canonical representations of quantum field theory and the role of zero-modes in this relation. The role of the underlying field algebra in the definition of the vacuum is exploited to understand these relations. The trivial vacuum defined by an annihilation operator defines a linear functional on the algebra of fields restricted to a light front. This is extended to a linear functional on the algebra of local fields. The extension defines a unitary mapping between the physical representation of the local algebra and a sub-algebra of the light-front Fock algebra. The dynamics appears in the mapping and the structure of the sub-algebra. This correspondence provides a formulation of locality and Poincaré invariance on the light-front Fock space. Zero modes do not appear in the final mapping, but may be needed in the construction of the mapping using a local Lagrangian.

Several arguments suggest that the entropy density at high energy density $\rho$ should be given by the expression $s=K\sqrt{\rho /G}$, where $K$ is a constant of order unity. On the other hand the covariant entropy bound requires that the entropy on a light sheet be bounded by $A/4G$, where $A$ is the area of the boundary of the sheet. We find that in a suitably chosen cosmological geometry, the above expression for $s$ violates the covariant entropy bound. We consider different possible explanations for this fact, in particular, the possibility that entropy bounds should be defined in terms of volumes of regions rather than areas of surfaces.

We compute the off-shell spectrum of supergravity on ${\mathrm{AdS}}_2\times S^2$ by explicit diagonalization of the equations of motion for an effective ${\mathrm{AdS}}_2$ theory where all fields are dualized to scalars and spin-$\frac{1}{2}$ fermions. We classify all bulk modes as physical, gauge violating, and pure gauge then compute the physical spectrum by explicit cancellation of unphysical modes. We identify boundary modes as physical fields on $S^2$ that are formally pure gauge but with gauge function that is non-normalizable on ${\mathrm{AdS}}_2$. As an application we compute the leading quantum correction to ${\mathrm{AdS}}_2\times S^2$ as a sum over physical fields including boundary states. The result agrees with a previous computation by Sen [1] where unphysical modes were canceled by ghosts.

We show that dissipative effects have a significant impact on the evolution of cosmological scalar fields, leading to friction, entropy production and field fluctuations. We explicitly compute the dissipation coefficient for different scalar fields within the standard model and some of its most widely considered extensions, in different parametric regimes. We describe the generic consequences of fluctuation-dissipation dynamics in the postinflationary universe, focusing in particular on friction and particle production, and analyze in detail two important effects. First, we show that dissipative friction delays the process of spontaneous symmetry breaking and may even damp the motion of a Higgs field sufficiently to induce a late period of warm inflation. Along with dissipative entropy production, this may parametrically dilute the abundance of dangerous thermal relics. Second, we show that dissipation can generate the observed baryon asymmetry without symmetry restoration, and we develop in detail a model of dissipative leptogenesis. We further show that this generically leads to characteristic baryon isocurvature perturbations that can be tested with cosmic microwave background observations. This work provides a fundamental framework to go beyond the leading thermal equilibrium semiclassical approximation in addressing fundamental problems in modern cosmology.

We set conservative, robust constraints on the annihilation and decay of dark matter into various Standard Model final states under various assumptions about the distribution of the dark matter in the Milky Way halo. We use the inclusive photon spectrum observed by the Fermi Gamma-ray Space Telescope through its main instrument, the Large Area Telescope. We use simulated data to first find the “optimal” regions of interest in the $\gamma$-ray sky, where the expected dark matter signal is largest compared with the expected astrophysical foregrounds. We then require the predicted dark matter signal to be less than the observed photon counts in the a priori optimal regions. This yields a very conservative constraint as we do not attempt to model or subtract astrophysical foregrounds. The resulting limits are competitive with other existing limits and, for some final states with cuspy dark-matter distributions in the Galactic Center region, disfavor the typical cross section required during freeze-out for a weakly interacting massive particle to obtain the observed relic abundance.

The photometry profile of the integrated Sachs-Wolfe (ISW) effect, recently obtained by the Planck consortium by stacking patches of cosmic microwave background (CMB) sky maps around a large number of cosmic voids, contains a cold ring at about half the void’s effective radius surrounded by a hot ring near the void’s boundary. The source of the temperature structure is assumed to be the ISW effect but the exact cause of the ringed structure is not currently well understood, particularly the outer hot ring. Numerical simulations have suggested that hot/cold ring structures can be produced by motions associated with nonlinear growths of cosmic structures whose gravitational potentials produce the ISW effect. We have recently developed the embedded lens theory and the Fermat potential formalism which can be used to model the ISW effect caused by intervening individual lens inhomogeneities evolving arbitrarily. This theory only requires knowledge of the void’s projected mass profile as a function of the passing CMB photons’ impact radius and the rate of change of that mass distribution at passage. We present two simple embedded void lens models with evolving mass densities and investigate the ISW effect caused by these lenses. Both models possess expanding mass shells which produce hot rings around central cold regions, consistent with the recent observations. By adding a small overdensity at the void’s center we can produce the slight positive temperature excess hinted at in Planck’s photometric results. We conclude that the embedded lens theory and the Fermat potential formalism is well suited for modeling the ISW effect.

The twin-peak high-frequency quasiperiodic oscillations (HFQPOs), observed in the power spectra of low-mass x-ray binaries, might carry relevant clues about the physics laws reigning close to a compact object. Their frequencies are typical of the orbital motion time scales a few gravitational radii away from the compact object. The aim of the manuscript is to propose an intuitive model explaining that the energy carried by the lower high-frequency quasiperiodic oscillation can be related to differences of potential energy released by clumps of plasma spiraling in a curved space-time. Our model provides estimates on both the size of clumps of matter that can survive to the strong tidal force and energy loaded by tides on the clump. We also have obtained some constrains on the mechanical properties of the plasma orbiting into the accretion disk. We note that the systematic behavior of the emitted energy as a function of the central frequency of the lower HFQPO, observed in several sources with a neutron star, might give clues related to an innermost stable bound orbit predicted by the general relativity theory in strong field regime.

We study the two-body baryonic $B$ and $D_s$ decays based on the annihilation mechanism without the partial conservation of the axial-vector current (PCAC) at the GeV scale. We demonstrate that the contributions of $B^{-}\to \mathrm{\Lambda }\overline{p}$, $B^{-}\to {\mathrm{\Sigma }}^0\overline{p}$, and ${\overline{B}}_s^0\to \mathrm{\Lambda }\overline{\mathrm{\Lambda }}$ are mainly from the scalar and pseudoscalar currents with their branching ratios predicted to be around $(3.5,5.3,5.3)\times 10^{-8}$, respectively, exactly the sizes of $\mathcal{B}(B\to \mathbf{B}{\overline{\mathbf{B}}}^{\prime })$ established by the data. We also apply the annihilation mechanism to all of the charmless two-body baryonic $B$ and $D_s$ decays. In particular, we can explain $\mathcal{B}({\overline{B}}_{(s)}^0\to p\overline{p})$ of order $10^{-8}$ and $\mathcal{B}(D_s^{+}\to p\overline{n})$ of order $10^{-3}$, which are from the axial-vector currents. In addition, the branching ratios of ${\overline{B}}^0\to \mathrm{\Lambda }\overline{\mathrm{\Lambda }}$, $B^{-}\to n\overline{p}$, and $B^{-}\to {\mathrm{\Sigma }}^{-}{\overline{\mathrm{\Sigma }}}^0$ are predicted to be $(0.3,3.2,9.6)\times 10^{-8}$, which can be measured by LHCb and viewed as tests for the violation of the partial conservation of the axial-vector current at the GeV scale.

The light hadron states are satisfactorily described in the quark model using $SU(3)$ flavor symmetry. If the $SU(3)$ flavor symmetry relating the light hadrons were exact, one would have an exchange symmetry between these hadrons arising out of the exchange of the up, down and strange quarks. This aspect of $SU(3)$ symmetry is used extensively to relate many decay modes of heavy quarks. However, the nature of the effects of $SU(3)$ breaking in such decays is not well understood, and hence a reliable estimate of $SU(3)$ breaking effects is missing. In this work we propose a new method to quantitatively estimate the extent of flavor symmetry breaking and better understand the nature of such breaking using the Dalitz plot. We study the three noncommuting $SU(2)$ symmetries [subsumed in $SU(3)$ flavor symmetry], isospin (or $T$-spin), $U$-spin and $V$-spin, using the Dalitz plots of some three-body meson decays. We look at the Dalitz plot distributions of decays in which pairs of the final three particles are related by two distinct $SU(2)$ symmetries. We show that such decay modes have characteristic distributions that enable the measurement of violation of each of the three $SU(2)$ symmetries via Dalitz plot asymmetries in a single decay mode. Experimental estimates of these easily measurable asymmetries would help in better understanding the weak decays of heavy mesons into both two and three light mesons.

We investigate the impact of light ($\sim \mathrm{eV}$) sterile neutrinos in the long-baseline experiment T2K. We show that, within the $3+1$ scheme, for mass-mixing parameters suggested by the short-baseline anomalies, the interference among the sterile and the atmospheric oscillation frequencies induces a new term in the ${\nu }_{\mu }\to {\nu }_e$ transition probability, which has the same order of magnitude of the standard 3-flavor solar-atmospheric interference term. We show, for the first time, that current T2K data, taken together with the results of the ${\theta }_{13}$-dedicated reactor experiments, are sensitive to two of the three $CP$-violating phases involved in the $3+1$ scheme. Both the standard $CP$ phase and the new one (${\delta }_{13}\equiv \delta$ and ${\delta }_{14}$ in our parameterization choice) tend to have a common best-fit value ${\delta }_{13}\simeq {\delta }_{14}\simeq -\pi /2$. Quite intriguingly, the inclusion of sterile neutrino effects leads to better agreement between the two estimates of ${\theta }_{13}$ obtained, respectively, from reactors and T2K, which in the 3-flavor framework are slightly different.

Higgs couplings with gauge bosons are probed through $e^{-}{e}^{+}\to W^{-}{W}^{+}h$ in an effective Lagrangian framework. An ILC of 500 GeV center-of-mass energy with possible beam polarization is considered for this purpose. The reach of the ILC with integrated luminosity of $300{\mathrm{fb}}^{-1}$ in the determination of both the charge conjugation and parity ($CP$)-conserving and $CP$-violating parameters is obtained. Sensitivity of the probe of each of these couplings on the presence of other couplings is investigated. The most influential coupling parameters are ${\overline{c}}_W=-{\overline{c}}_B$. Other parameters of significant effect are ${\overline{c}}_{HW}$ and ${\overline{c}}_{HB}$ among the $CP$-conserving ones and ${\tilde{c}}_{HW}$ among the $CP$-violating ones. $CP$-violating parameters ${\tilde{c}}_{\gamma }$ and ${\tilde{c}}_{HB}$ are found to have very little influence on the process considered. A detailed study of the angular distributions presents a way to disentangle the effect of some of these couplings.

We report on measurements of neutrino oscillation using data from the T2K long-baseline neutrino experiment collected between 2010 and 2013. In an analysis of muon neutrino disappearance alone, we find the following estimates and 68% confidence intervals for the two possible mass hierarchies: $\text{normal hierarchy}:{\sin }^2{\theta }_{23}=0.514_{-0.056}^{+0.055}$ and $\mathrm{\Delta }{m}_{32}^2=(2.51\pm 0.10)\times 10^{-3}{\mathrm{eV}}^2/c^4$ and $\text{inverted hierarchy}:{\sin }^2{\theta }_{23}=0.511\pm 0.055$ and $\mathrm{\Delta }{m}_{13}^2=(2.48\pm 0.10)\times 10^{-3}{\mathrm{eV}}^2/c^4$. The analysis accounts for multinucleon mechanisms in neutrino interactions which were found to introduce negligible bias. We describe our first analyses that combine measurements of muon neutrino disappearance and electron neutrino appearance to estimate four oscillation parameters, $|\mathrm{\Delta }{m}^2|$, ${\sin }^2{\theta }_{23}$, ${\sin }^2{\theta }_{13}$, ${\delta }_{CP}$, and the mass hierarchy. Frequentist and Bayesian intervals are presented for combinations of these parameters, with and without including recent reactor measurements. At 90% confidence level and including reactor measurements, we exclude the region ${\delta }_{CP}=[0.15,0.83]\pi$ for normal hierarchy and ${\delta }_{CP}=[-0.08,1.09]\pi$ for inverted hierarchy. The T2K and reactor data weakly favor the normal hierarchy with a Bayes factor of 2.2. The most probable values and 68% one-dimensional credible intervals for the other oscillation parameters, when reactor data are included, are ${\sin }^2{\theta }_{23}=0.528_{-0.038}^{+0.055}$ and $|\mathrm{\Delta }{m}_{32}^2|=(2.51\pm 0.11)\times 10^{-3}{\mathrm{eV}}^2/c^4$.

Using the AdS/CFT correspondence, we construct the holographic dual of a tunneling instanton describing Schwinger pair creation in de Sitter space. Our approach allows us to extract the critical value of the electric field for which the potential barrier disappears, rendering the vacuum unstable. In addition, we compute the large-$\lambda$, large-$N_c$ corrections to the nucleation rate and we find that it agrees with previous expectations based on perturbative computations. As a by-product of this investigation, we study the causal structure of the string dual to the nucleated pair as seen by different static observers and we show that it can be interpreted as a dynamical creation of a “gluonic” wormhole. We explain how this result provides further evidence for the $\mathrm{ER}=\mathrm{EPR}$ conjecture as an equivalence between two descriptions of the same physical phenomenon.

Based on the analogy with superconductor physics we consider a scalar-vector-tensor gravitational model, in which the dark energy action is described by a gauge invariant electromagnetic type functional. By assuming that the ground state of the dark energy is in a form of a condensate with the U(1) symmetry spontaneously broken, the gauge invariant electromagnetic dark energy can be described in terms of the combination of a vector and of a scalar field (corresponding to the Goldstone boson), respectively. The gravitational field equations are obtained by also assuming the possibility of a nonminimal coupling between the cosmological mass current and the superconducting dark energy. The cosmological implications of the dark energy model are investigated for a Friedmann-Robertson-Walker homogeneous and isotropic geometry for two particular choices of the electromagnetic type potential, corresponding to a pure electric type field, and to a pure magnetic field, respectively. The time evolutions of the scale factor, matter energy density and deceleration parameter are obtained for both cases, and it is shown that in the presence of the superconducting dark energy the Universe ends its evolution in an exponentially accelerating vacuum de Sitter state. By using the formalism of the irreversible thermodynamic processes for open systems we interpret the generalized conservation equations in the superconducting dark energy model as describing matter creation. The particle production rates, the creation pressure and the entropy evolution are explicitly obtained.

We construct cosmological long-wavelength solutions without symmetry in general gauge conditions which are compatible with the long-wavelength scheme. We then specify the relationship among the solutions in different time slicings. Nonspherical long-wavelength solutions are particularly important for primordial structure formation in the epoch of very soft equations of state. Applying this general framework to spherical symmetry, we show the equivalence between long-wavelength solutions in the constant mean curvature slicing with conformally flat spatial coordinates and asymptotic quasihomogeneous solutions in the comoving slicing with the comoving threading. We derive the correspondence relation between these two solutions and compare the results of numerical simulations of primordial black hole (PBH) formation in these two different approaches. To discuss the PBH formation, it is convenient and conventional to use ${\tilde{\delta }}_c$, the value which the averaged density perturbation at threshold in the comoving slicing would take at horizon entry in the lowest-order long-wavelength expansion. We numerically find that within (approximately) compensated models, the sharper the transition from the overdense region to the Friedmann-Robertson-Walker universe is, the larger the ${\tilde{\delta }}_c$ becomes. We suggest that, for the equation of state $p=(\mathrm{\Gamma }-1)\rho$, we can apply the analytic formulas for the minimum ${\tilde{\delta }}_{c,\min }\simeq [3\mathrm{\Gamma }/(3\mathrm{\Gamma }+2)]{\sin }^2[\pi \sqrt{\mathrm{\Gamma }-1}/(3\mathrm{\Gamma }-2)]$ and the maximum ${\tilde{\delta }}_{c,\max }\simeq 3\mathrm{\Gamma }/(3\mathrm{\Gamma }+2)$. As for the threshold peak value of the curvature variable ${\psi }_{0,c}$, we find that the sharper the transition is, the smaller the ${\psi }_{0,c}$ becomes. We analytically explain this intriguing feature qualitatively with a compensated top-hat density model. Using simplified models, we also analytically deduce an environmental effect that ${\psi }_{0,c}$ can be significantly larger (smaller) if the underlying perturbation of much longer wavelength is positive (negative).

The standard approach to cosmic-ray (CR) propagation in the Galaxy is based on the assumption that local transport properties can be extrapolated to the whole CR confining volume. Such models tend to underestimate the $\gamma$-ray flux above a few GeV measured by the Fermi Large Area Telescope toward the inner Galactic plane. We consider here for the first time a phenomenological scenario allowing for both the rigidity scaling of the diffusion coefficient and the convective effects to be position dependent. We show that within this approach we can reproduce the observed $\gamma$-ray spectra at both low and mid Galactic latitudes—including the Galactic center—without spoiling any local CR observable.

Hadron masses can be decomposed as a sum of quark and glue components that are defined through hadronic matrix elements of QCD operators. The components consist of the quark mass term, the quark energy term, the glue energy term, and the trace anomaly term. We calculate these components for mesons with lattice QCD for the first time. The calculation is carried out with overlap fermion on $2+1$ flavor domain-wall fermion gauge configurations. We confirm that $\sim 50\%$ of the light pion mass comes from the quark mass term and $\sim 10\%$ comes from the quark energy; whereas, for the $\rho$ meson, the quark energy contributes roughly half of its mass but the quark mass term contributes little. The combined glue components contribute $\sim 40–50\%$ for both mesons. It is interesting to observe that the quark mass contribution to the mass of the vector meson is almost linear in quark mass over a large quark mass region below the charm quark mass. For heavy mesons, the quark mass term dominates the masses, while the contribution from the glue components is about 200 MeV (a bare value around 2 GeV) for the heavy pseudoscalar and vector mesons. The charmonium hyperfine splitting is found to be dominated by the quark energy term which is consistent with the picture of the quark potential model.