We introduce a new regularization scheme for Quantum Cosmology in Loop Quantum Gravity (LQG) using the tools of Quantum Reduced Loop Gravity (QRLG). It is obtained considering density matrices for superposition of graphs based on statistical countings of microstates compatible with macroscopic configurations. We call this procedure statistical regularization scheme. In particular, we show how the ${\mu }_0$ and $\overline{\mu }$ schemes introduced in Loop Quantum Cosmology (LQC) emerge with specific choices of density matrices. Within this new scheme we compute effective Hamiltonians suitable to describe quantum corrected Friedmann and Bianchi $I$ universes and their leading orders coincide with the corresponding effective LQC Hamiltonians in the $\overline{\mu }$ scheme. We compute the next to the leading orders corrections and numerical investigation of the resulting dynamics shows evidence for the emergent-bouncing universe scenario to be a general property of the isotropic sector of QRLG.

It has been shown earlier [Phys. Rev. D 72, 085006 (2005), Phys. Rev. D 73, 065010 (2006)] that, in the mixed space, there is an unexpected simple relation between any finite temperature graph and its zero temperature counterpart through a multiplicative scalar operator (termed thermal operator) which carries the entire temperature dependence. This holds only in the imaginary time formalism and the closed time path ($\sigma =0$) of the real time formalism (as well as for its conjugate $\sigma =1$). We study the origin of this operator from the more fundamental Bogoliubov transformation which acts, in the momentum space, on the doubled space of fields in the real time formalisms [Collective Phenomena 2, 55 (1975), Int. J. Mod. Phys. B 10, 1755 (1996), Thermo Field Dynamics and Condensed States (North-Holland, Amsterdam, 1982), Phys. Rev. D 93, 125028 (2016)]. We show how the ($2\times 2$) Bogoliubov transformation matrix naturally leads to the scalar thermal operator for $\sigma =0$, 1 while it fails for any other value $0<\sigma <1$. This analysis also suggests that a generalized scalar thermal operator description, in the mixed space, is possible even for $0<\sigma <1$. We also show the existence of a scalar thermal operator relation in the momentum space.

We perform magnetohydrodynamic simulations in full general relativity of disk accretion onto nonspinning black hole binaries with mass ratio $q=29/36$. We survey different disk models which differ in their scale height, total size and magnetic field to quantify the robustness of previous simulations on the initial disk model. Scaling our simulations to LIGO GW150914 we find that such systems could explain possible gravitational wave and electromagnetic counterparts such as the Fermi GBM hard x-ray signal reported 0.4 s after GW150915 ended. Scaling our simulations to supermassive binary black holes, we find that observable flow properties such as accretion rate periodicities, the emergence of jets throughout inspiral, merger and postmerger, disk temperatures, thermal frequencies, and the time delay between merger and the boost in jet outflows that we reported in earlier studies display only modest dependence on the initial disk model we consider here.

Taking the Planck cosmic microwave background data and the more direct Hubble constant measurement data as unaffected by systematic offsets, the values of the Hubble constant $H_0$ interpreted within the $\mathrm{\Lambda }\mathrm{CDM}$ cosmological constant and cold dark matter cosmological model are in $\sim 3.3\sigma$ tension. We show that the Parker vacuum metamorphosis (VM) model, physically motivated by quantum gravitational effects and with the same number of parameters as $\mathrm{\Lambda }\mathrm{CDM}$, can remove the $H_0$ tension and can give an improved fit to data (up to a mean $\mathrm{\Delta }{\chi }^2=-7.5$). It also ameliorates tensions with weak lensing data and the high redshift Lyman alpha forest data. Considering Bayesian evidence, we found in the case of the Planck data set alone positive evidence for a VM model against a cosmological constant both in the six- and nine-parameter framework. When the R16 data set is also considered, we found a strong evidence for the VM model against a cosmological constant in nine-parameter space. We separately consider a scale-dependent scaling of the gravitational lensing amplitude, such as provided by modified gravity, neutrino mass, or cold dark energy, motivated by the somewhat different cosmological parameter estimates for low and high CMB multipoles. We find that no such scale dependence is preferred.

The primordial B-modes component of the cosmic microwave background (CMB) polarization is a promising experimental data set to probe the inflationary paradigm. B modes are indeed a direct consequence of the presence of gravitational waves in the early Universe. However, several secondary effects in the low-redshift universe will produce nonprimordial B modes. In particular, the gravitational interactions of CMB photons with large-scale structures will distort the primordial E modes, adding a lensing B-mode component to the primordial signal. Removing the lensing component (“delensing”) will then be necessary to constrain the amplitude of the primordial gravitational waves. Here, we examine the role of current and future large-scale structure surveys in a multitracers approach to CMB delensing. We find that, in general, galaxy surveys should be split into tomographic bins, as this can increase the reduction of lensing B modes by $\sim 25\%$ in power in the most futuristic case. Ongoing or recently completed CMB experiments will particularly benefit from large-scale structure tracers that, once properly combined, will have a better performance than a CMB internal reconstruction. With the decrease of instrumental noise, the lensing B-modes power removed using CMB internal reconstruction alone will rapidly increase. Nevertheless, optical galaxy surveys will still play an important role even for fourth-generation CMB experiments. In particular, an LSST-like survey can a achieve a delensing performance comparable to a third-generation CMB experiment but with entirely different systematics. This redundancy will be essential to demonstrate the robustness against systematics of an eventual detection of primordial B modes.

We compare binary evolution models with different assumptions about black-hole natal kicks to the first gravitational-wave observations performed by the LIGO detectors. Our comparisons attempt to reconcile merger rate, masses, spins, and spin-orbit misalignments of all current observations with state-of-the-art formation scenarios of binary black holes formed in isolation. We estimate that black holes (BHs) should receive natal kicks at birth of the order of $\sigma \simeq 200(50)\mathrm{km}/\mathrm{s}$ if tidal processes do (not) realign stellar spins. Our estimate is driven by two simple factors. The natal kick dispersion $\sigma$ is bounded from above because large kicks disrupt too many binaries (reducing the merger rate below the observed value). Conversely, the natal kick distribution is bounded from below because modest kicks are needed to produce a range of spin-orbit misalignments. A distribution of misalignments increases our models’ compatibility with LIGO’s observations, if all BHs are likely to have natal spins. Unlike related work which adopts a concrete BH natal spin prescription, we explore a range of possible BH natal spin distributions. Within the context of our models, for all of the choices of $\sigma$ used here and within the context of one simple fiducial parameterized spin distribution, observations favor low BH natal spin.

The recent observations of gravitational-wave and electromagnetic emission produced by the merger of the binary neutron-star system GW170817 have opened the possibility of using standard sirens to constrain the value of the Hubble constant. While the reported bound of $H_0=70_{-8}^{+12}$ at 68% C.L. is significantly weaker than those recently derived by observations of Cepheid variables, it does not require any form of cosmic distance ladder and can be considered as complementary and, in principle, more conservative. Here we combine, for the first time, the new measurement with the Planck cosmic microwave background (CMB) observations in a 12 parameter extended $\mathrm{\Lambda }\mathrm{CDM}$ scenario, where the Hubble constant is weakly constrained from CMB data alone and bound to a low value $H_0=55_{-20}^{+7}\mathrm{km}/\mathrm{s}/\mathrm{Mpc}$ at 68% C.L. We point out that the non-Gaussian shape of the GW170817 bound makes lower values of the Hubble constant in worse agreement with observations than what is expected from a Gaussian form. The inclusion of the new GW170817 Hubble constant measurement therefore significantly reduces the allowed parameter space, improving the cosmological bounds on several parameters as the neutrino mass, curvature, and dark energy equation of state.

We study the trident process in inhomogeneous plane-wave background fields. We obtain compact analytical expressions for all terms in the probability, including the exchange part, for an arbitrarily shaped plane wave. We evaluate the probability numerically using complex deformation of light-front time integrals and derive various analytical approximations. Our results provide insights into the importance of the one-step and exchange parts of the probability relative to the two-step process, and into the convergence to the locally constant field approximation.

The clockwork mechanism for gravity introduces a tower of massive graviton modes, clockwork gravitons, with a very compressed mass spectrum, whose interaction strengths are much stronger than those of massless gravitons. In this work, we compute the lowest order contributions of the clockwork gravitons to the anomalous magnetic moment, $g-2$, of muon in the context of an extra dimensional model with a five-dimensional Planck mass, $M_5$. We find that the total contributions are rather insensitive to the detailed model parameters and are determined mostly by the value of $M_5$. To account for the current muon $g-2$ anomaly, $M_5$ should be around 0.2 TeV, and the size of the extra dimension has to be quite large, $l_5\gtrsim {10}^{-7}\mathrm{m}$. For $M_5\gtrsim 1\mathrm{TeV}$, the clockwork graviton contributions are too small to explain the current muon $g-2$ anomaly. We also compare the clockwork graviton contributions with other extra dimensional models such as Randall-Sundrum models or large extra dimensional models. We find that the leading contributions in the small curvature limit are universal, but the cutoff-independent subleading contributions vary for different background geometries and the clockwork geometry gives the smallest subleading contributions.

We study double parton scattering (DPS) processes involving electroweak gauge bosons at the 13 and 100 TeV proton-proton colliders. Specifically, we focus on three DPS channels: $W$-boson plus two jets ($W\otimes jj$), $Z$-boson plus two jets ($Z\otimes jj$), and same-sign $W$ pair production ($W^{\pm }\otimes W^{\pm }$). We demonstrate that the $Z\otimes jj$ process, which has not received much attention, is the best channel for measuring the effective cross section ${\sigma }_{\mathrm{eff}}$. The accuracy of the ${\sigma }_{\mathrm{eff}}$ measurement in the three DPS channels, especially the $W^{\pm }\otimes W^{\pm }$ production, is significantly improved at the 100 TeV colliders. We advocate that combined analysis of the three DPS channels could test the universality of the effective cross section ${\sigma }_{\mathrm{eff}}$.

Naturalness arguments applied to simple supersymmetric (SUSY) theories require a set of light higgsinos with mass $\sim |\mu |$ not too far from $m_h$. These models have an inverted electroweakino spectrum with $|\mu |\ll M_2$ which leads to a rather clean, hadronically quiet, same-sign diboson (SSdB) signature at hadron colliders arising from neutral-plus-charged wino pair production. We improve and expand our earlier studies of this signature for discovering SUSY in natural SUSY models by (i) including backgrounds which were not previously considered and which turn out to be significant, (ii) devising more efficient cuts to successfully contend with these larger backgrounds and determining the discovery reach and exclusion ranges for winos with these cuts, emphasizing projections for the updated integrated luminosity target for HL-LHC of $3{\mathrm{ab}}^{-1}$, and (iii) emphasizing the utility of this channel for natural models without gaugino mass unification. We display the kinematic characteristics of the relatively jet-free same sign $\mathrm{dilepton}+{\cancel{E}}_T$ events (from leptonic decays of both $W\mathrm{s}$) and find that these are only weakly sensitive to the parent wino mass. We also examine the charge asymmetry in these events and show that its measurement can be used to check the consistency of the wino origin of the signal. Finally, we show that—because the wino branching fractions in natural SUSY are essentially independent of details of the underlying model—a determination of the rate for clean, same-sign dilepton events yields a better than 10% determination of the wino mass over the entire mass range where experiments at the HL-LHC can discover the wino signal.

A lattice QCD determination of the ${\mathrm{\Lambda }}_c\to N$ vector, axial vector, and tensor form factors is reported. The calculation was performed with $2+1$ flavors of domain-wall fermions at lattice spacings of $a\approx 0.11$ and 0.085 fm and pion masses in the range $230\mathrm{MeV}\lesssim m_{\pi }\lesssim 350\mathrm{MeV}$. The form factors are extrapolated to the continuum limit and the physical pion mass using modified $z$ expansions. The rates of the charged-current decays ${\mathrm{\Lambda }}_c\to n{e}^{+}{\nu }_e$ and ${\mathrm{\Lambda }}_c\to n{\mu }^{+}{\nu }_{\mu }$ are predicted to be $(0.405\pm 0.016_{\mathrm{stat}}\pm 0.020_{\mathrm{syst}})|V_{cd}{|}^2{\mathrm{ps}}^{-1}$ and $(0.396\pm 0.016_{\mathrm{stat}}\pm 0.020_{\mathrm{syst}})|V_{cd}{|}^2{\mathrm{ps}}^{-1}$, respectively. The phenomenology of the rare charm decay ${\mathrm{\Lambda }}_c\to p{\mu }^{+}{\mu }^{-}$ is also studied. The differential branching fraction, the fraction of longitudinally polarized dimuons, and the forward-backward asymmetry are calculated in the standard model and in an illustrative new-physics scenario.

Gauged Gaussian projected entangled pair states are particular tensor network constructions that describe lattice states of fermionic matter interacting with dynamical gauge fields. We show how one can efficiently compute, using Monte Carlo techniques, expectation values of physical observables in that class of states. This opens up the possibility of using tensor network techniques to investigate lattice gauge theories in two and three spatial dimensions.

We study neutral and charged meson properties in the magnetic field. Taking the bosonization method in a two-flavor Nambu–Jona-Lasinio model, we derive effective meson Lagrangian density with minimal coupling to the magnetic field, by employing derivative expansion for both the meson fields and Schwinger phases. We extract from the effective Lagrangian density the meson curvature, pole and screening masses. As the only Goldstone mode, the neutral pion controls the thermodynamics of the system and propagates the long range quark interaction. The magnetic field breaks down the space symmetry, and the quark interaction region changes from a sphere in vacuum to a ellipsoid in magnetic field.

We study the behavior of neutral meson properties in the presence of a static uniform external magnetic field in the context of nonlocal chiral quark models. The formalism is worked out introducing Ritus transforms of Dirac fields, which allow to obtain closed analytical expressions for ${\pi }^0$ and $\sigma$ meson masses and for the ${\pi }^0$ decay constant. Numerical results for these observables are quoted for various parametrizations. In particular, the behavior of the ${\pi }^0$ meson mass with the magnetic field is found to be in good agreement with lattice QCD results. It is also seen that the Goldberger-Treiman and Gell-Mann-Oakes-Renner chiral relations remain valid within these models in the presence of the external magnetic field.

We extend our recent works on the two-pion $S$-wave resonance contributions to the kaon-pion ones in the $B$ meson hadronic charmonium decay modes based on the perturbative QCD approach. The $S$-wave $K\pi$ timelike form factor in its distribution amplitudes is described by the LASS parametrization, which consists of the $K_0^{*}(1430)$ resonant state together with an effective range nonresonant component. The predictions for the decays $B\to J/\psi K\pi$ in this work agree well with the experimental results from the BABAR and Belle collaborations. We also discuss theoretical uncertainties, indicating that the results of this work, which can be tested by the LHCb and Belle-II experiments, are reasonably accurate.

Sensitivity of the magnetized Iron Calorimeter (ICAL) detector at the proposed India-based Neutrino Observatory (INO) to invisible decay of the mass eigenstate ${\nu }_3$ using atmospheric neutrinos is explored. A full three-generation analysis including Earth matter effects is performed in a framework with both decay and oscillations. The wide energy range and baselines offered by atmospheric neutrinos are shown to be excellent for constraining the ${\nu }_3$ lifetime. We find that with an exposure of $500\mathrm{kton}-\mathrm{yr}$ the ICAL atmospheric experiment could constrain the ${\nu }_3$ lifetime to ${\tau }_3/m_3>1.51\times {10}^{-10}\mathrm{s}/\mathrm{eV}$ at the 90% C.L. This is 2 orders of magnitude tighter than the bound from MINOS. The effect of invisible decay on the precision measurement of ${\theta }_{23}$ and $|\mathrm{\Delta }{m}_{32}^2|$ is also studied.

Classically, the black hole (BH) horizon is completely opaque, hiding any clues about the state and very existence of its interior. Quantum mechanically and in equilibrium, the situation is not much different; Hawking radiation will now be emitted, but it comes out at an extremely slow rate, is thermal to a high degree of accuracy, and thus carries a minimal amount of information about the quantum state within the BH. Here, it is shown that the situation is significantly different when a quantum BH is out of equilibrium. We argue that the BH can then emit “supersized” Hawking radiation with a much larger amplitude than that emitted in equilibrium. The result is a new type of quantum hair that can reveal the state and composition of the BH interior to an external observer. Moreover, the frequency and amplitude of the new hair can be explained by the observer without invoking any new physical principles. The new hair decays at a parametrically slow rate in comparison to the Schwarzschild time scale and can be detected through the emission of gravitational waves (and possibly other types of waves) whenever a BH has received a large enough surge in energy to move it far away from its equilibrium state, in particular, during and immediately after a BH-merger event. The current discussion is motivated by a previous analysis, in the context of a recently proposed polymer model for the BH interior, that implies emissions just like those described here. We expect, however, that the new hair is a model-independent property of quantum BHs.

We consider theories describing the dynamics of a four-dimensional metric, whose Lagrangian is diffeomorphism invariant and depends at most on second derivatives of the metric. Imposing degeneracy conditions we find a set of Lagrangians that, apart form the Einstein-Hilbert one, are either trivial or contain more than 2 degrees of freedom. Among the partially degenerate theories, we recover Chern-Simons gravity, endowed with constraints whose structure suggests the presence of instabilities. Then, we enlarge the class of parity violating theories of gravity by introducing new “chiral scalar-tensor theories.” Although they all raise the same concern as Chern-Simons gravity, they can nevertheless make sense as low energy effective field theories or, by restricting them to the unitary gauge (where the scalar field is uniform), as Lorentz breaking theories with a parity violating sector.