We present a largely model-independent analysis of the lighter heavy quarkonium hybrids based on the strong coupling regime of potential nonrelativistic QCD. We calculate the spectrum at leading order, including the mixing of static hybrid states. We use potentials that fulfill the required short and long distance theoretical constraints and fit well the available lattice data. We argue that the decay width to the lower lying heavy quarkonia can be reliably estimated in some cases and provide results for a selected set of decays. We also consider the mixing with heavy quarkonium states. We establish the form of the mixing potential at $O(1/m_Q)$, $m_Q$ being the mass of the heavy quarks, and work out its short and long distance constraints. The weak coupling regime of potential nonrelativistic QCD and the effective string theory of QCD are used for that goal. We show that the mixing effects may indeed be important and produce large spin symmetry violations. Most of the isospin zero XYZ states fit well in our spectrum, either as a hybrid or standard quarkonium candidate.

We investigate the photoproduction of the $\mathrm{\Lambda }(1405)\equiv {\mathrm{\Lambda }}^{*}$ hyperon resonance, i.e., $\gamma p\to K^{+}{\mathrm{\Lambda }}^{*}$, employing the effective Lagrangian approach with the $t$-channel Regge trajectories at tree level. We extensively explore the effects from the nucleon resonances in the vicinity of the threshold ${\sqrt{s}}_{\mathrm{th}}\approx 1900\mathrm{MeV}$, i.e., $N^{*}(2000)$, $N^{*}(2030)$, $N^{*}(2055)$, $N^{*}(2095)$, and $N^{*}(2100)$, and observe that they are of great importance to reproduce the recent CLAS experimental data. Total and differential cross sections are given as numerical results and compared with the experimental data, in addition to the photon-beam asymmetry. The invariant-mass distributions for $\gamma p\to K^{+}{\pi }^0{\mathrm{\Sigma }}^0$ via ${\mathrm{\Lambda }}^{*}$ are also extracted from the two-body process results, showing a qualitative agreement with the data. We also discuss the constituent-counting rule for the internal structure of ${\mathrm{\Lambda }}^{*}$, resulting in that ${\mathrm{\Lambda }}^{*}$ appears to be different from a simple three-quark ($uds$) state.

T2HK and T2HKK are the proposed extensions of the T2K experiments in Japan and DUNE is the future long-baseline program of Fermilab. These three experiments will use extremely high beam power and large detector volumes to observe neutrino oscillation. Because of the large statistics, these experiments will be highly sensitive to systematics. Thus a small change in the systematics can cause a significant change in their sensitivities. To understand this, we do a comparative study of T2HK, T2HKK, and DUNE with respect to their systematic errors. Specifically we study the effect of the systematics in the determination of neutrino mass hierarchy, octant of the mixing angle ${\theta }_{23}$, and ${\delta }_{CP}$ in the standard three-flavor scenario, and we also analyze the role of systematic uncertainties in constraining the parameters of the nonstandard interactions in neutrino propagation. Taking the overall systematics for signal and background normalization, we quantify how the sensitivities of these experiments change if the systematics are varied from 1% to 7%.

We observe for the first time the process $e^{+}{e}^{-}\to \eta h_c$ with data collected by the BESIII experiment. Significant signals are observed at the center-of-mass energy $\sqrt{s}=4.226\mathrm{GeV}$, and the Born cross section is measured to be $(9.5_{-2.0}^{+2.2}\pm 2.7)\mathrm{pb}$. Evidence for $\eta h_c$ is observed at $\sqrt{s}=4.358\mathrm{GeV}$ with a Born cross section of $(10.0_{-2.7}^{+3.1}\pm 2.6)\mathrm{pb}$, and upper limits on the production cross section at other center-of-mass energies between 4.085 and 4.600 GeV are determined.

We compute the decay rate of dimuonium into a neutral pion and a photon. We find that approximately one in $10^5$ orthodimuonia decays into this channel. We also determine the contribution of the virtual photon-pion loop to the hyperfine splitting in dimuonium and reproduce its leading effect in the anomalous magnetic moment of the muon.

A hard three-loop correction to parapositronium energy levels of order $m{\alpha }^7$ is calculated. This nonlogarithmic contribution is due to the insertions of one-loop photon propagator in the fermion lines in the diagrams with virtual two-photon annihilation. We obtained $\mathrm{\Delta }E=0.03297(2)(m{\alpha }^7/{\pi }^3)$ for this energy shift.

The holographic model of V-QCD is used to analyze the physics of QCD in the Veneziano large-N limit. An unprecedented analysis of the $CP$-odd physics is performed going beyond the level of effective field theories. The structure of holographic saddle points at finite $\theta$ is determined, as well as its interplay with chiral symmetry breaking. Many observables (vacuum energy and higher-order susceptibilities, singlet and nonsinglet masses and mixings) are computed as functions of $\theta$ and the quark mass $m$. Wherever applicable the results are compared to those of chiral Lagrangians, finding agreement. In particular, we recover the Witten-Veneziano formula in the small $x\to 0$ limit, we compute the $\theta$ dependence of the pion mass, and we derive the hyperscaling relation for the topological susceptibility in the conformal window in terms of the quark mass.

We consider the possibility of gauge coupling unification within the simplest realizations of the $\mathrm{SU}(3{)}_{\mathrm{c}}\times \mathrm{SU}(3{)}_{\mathrm{L}}\times \mathrm{SU}(3{)}_{\mathrm{R}}\times \mathrm{U}(1{)}_{\mathrm{X}}$ gauge theory. We present a first exploration of the renormalization group equations governing the “bottom-up” evolution of the gauge couplings in a generic model with free normalization for the generators. Interestingly, we find that for a $\mathrm{SU}(3{)}_{\mathrm{c}}\times \mathrm{SU}(3{)}_{\mathrm{L}}\times \mathrm{SU}(3{)}_{\mathrm{R}}\times \mathrm{U}(1{)}_{\mathrm{X}}$ symmetry breaking scale $M_X$ as low as a few TeV one can achieve unification in the presence of leptonic octets. We briefly comment on possible grand unified theory frameworks which can embed the $\mathrm{SU}(3{)}_{\mathrm{c}}\times \mathrm{SU}(3{)}_{\mathrm{L}}\times \mathrm{SU}(3{)}_{\mathrm{R}}\times \mathrm{U}(1{)}_{\mathrm{X}}$ model as well as possible implications, such as lepton flavor violating physics at the LHC.

We find a realization of the $Z_2$ symmetry in the neutrino mass matrix which expresses a rotation of the $\mu -\tau$ symmetry and is able to impose a generic smallest mixing angle, in contrast to a zero-value predicted by the usual nonrotated form of the $\mu -\tau$ symmetry. We extend this symmetry for the lepton sector within the type-I seesaw scenario and show it can accommodate the mixing angles, the mass hierarchies, and the lepton asymmetry in the Universe. We then study the effects of perturbing the specific form of the neutrino mass matrix imposed by the symmetry and compute the resulting mixing and mass spectrum. We trace back this “low-scale” perturbation to a “high-scale” perturbation, and find realizations of this latter one arising from exact symmetries with an enriched matter content.

We explore in greater detail our investigations of shear diffusion in hyperscaling violating Lifshitz theories in Phys. Lett. B 760, 86 (2016). This adapts and generalizes the membrane-paradigm-like analysis of Kovtun, Son, and Starinets for shear gravitational perturbations in the near horizon region given certain self-consistent approximations, leading to the shear diffusion constant on an appropriately defined stretched horizon. In theories containing a gauge field, some of the metric perturbations mix with some of the gauge field perturbations and the above analysis is somewhat more complicated. We find a similar near-horizon analysis can be obtained in terms of new field variables involving a linear combination of the metric and the gauge field perturbation resulting in a corresponding diffusion equation. Thereby as before, for theories with Lifshitz and hyperscaling violating exponents $z$, $\theta$ satisfying $z<4-\theta$ in four bulk dimensions, our analysis here results in a similar expression for the shear diffusion constant with power-law scaling with temperature suggesting universal behavior in relation to the viscosity bound. For $z=4-\theta$, we find logarithmic behavior.

Using self-dual Ashtekar variables, we investigate (at the effective level) the spherically symmetry reduced model of loop quantum gravity, both in vacuum and when coupled to a scalar field. Within the real Ashtekar-Barbero formulation, the system scalar field coupled to spherically symmetric gravity is known to possess a non closed (quantum) algebra of constraints once local (pointwise) holonomy corrections are introduced, which leads to several obstructions in the loop quantization of the model. Moreover, the vacuum case, while not anomalous, introduces modifications which have been suggested to be an effective signature change of the metric in the deep quantum region. We show in this paper that both those complications disappear when working with self-dual Ashtekar variables, both in the vacuum case and in the case of gravity minimally coupled to a scalar field. In this framework, the algebra of the holonomy corrected constraints is anomaly free and reproduces the classical hypersurface deformation algebra without any deformations. A possible path towards quantization of this model is briefly discussed.

We continue a previous study about the infrared loop effects in the $D$-dimensional de Sitter space for a real scalar ${\varphi }^4$ theory from the complementary series whose bare mass belongs to the interval $\frac{\sqrt{3}}{4}(D-1)<m\le \frac{D-1}{2}$, in units of the Hubble scale. The lower bound comes from the appearance of discrete states in the mass spectrum of the theory when that bound is violated, causing large IR loop effects in the vertices. We derive an equation which allows us to perform a self-consistent resummation of the leading IR contributions from all loops to the two-point correlation functions in an expanding Poincaré patch of the de Sitter manifold. The resummation can be done for density perturbations of the Bunch-Davies state which violate the de Sitter isometry. There exist solutions having a singular (exploding) behavior, and therefore the backreaction can change the de Sitter geometry.

The present work is the second part of a series of computations for the self-mass-squared of the conformally coupled (CC) scalar interacting with gravitons. This work includes the kinetic-kinetic and kinetic-conformal parts, and thus completes the full scalar self-mass-squared at one loop order in de Sitter background when combined with the conformal-conformal part previously evaluated. We use dimensional regularization and renormalize the results by subtracting appropriate counterterms. The self-mass squared is finally ready to quantum-correct the CC scalar field equation so that one can study the effect of inflationary produced gravitons on the CC scalar and its observational consequences.

Binary systems containing boson stars—self-gravitating configurations of a complex scalar field—can potentially mimic black holes or neutron stars as gravitational-wave sources. We investigate the extent to which tidal effects in the gravitational-wave signal can be used to discriminate between these standard sources and boson stars. We consider spherically symmetric boson stars within two classes of scalar self-interactions: an effective-field-theoretically motivated quartic potential and a solitonic potential constructed to produce very compact stars. We compute the tidal deformability parameter characterizing the dominant tidal imprint in the gravitational-wave signals for a large span of the parameter space of each boson star model, covering the entire space in the quartic case, and an extensive portion of interest in the solitonic case. We find that the tidal deformability for boson stars with a quartic self-interaction is bounded below by ${\mathrm{\Lambda }}_{\min }\approx 280$ and for those with a solitonic interaction by ${\mathrm{\Lambda }}_{\min }\approx 1.3$. We summarize our results as ready-to-use fits for practical applications. Employing a Fisher matrix analysis, we estimate the precision with which Advanced LIGO and third-generation detectors can measure these tidal parameters using the inspiral portion of the signal. We discuss a novel strategy to improve the distinguishability between black holes/neutrons stars and boson stars by combining tidal deformability measurements of each compact object in a binary system, thereby eliminating the scaling ambiguities in each boson star model. Our analysis shows that current-generation detectors can potentially distinguish boson stars with quartic potentials from black holes, as well as from neutron-star binaries if they have either a large total mass or a large (asymmetric) mass ratio. Discriminating solitonic boson stars from black holes using only tidal effects during the inspiral will be difficult with Advanced LIGO, but third-generation detectors should be able to distinguish between binary black holes and these binary boson stars.

It is generally believed that the concept of the spacetime continuum should be modified for distances as small as the Planck length. This is a length scale at which the spacetime might have a discrete structure and quantum gravity effects are dominant. Presumably, the microscopic fluctuations within the geometry of spacetime should result in an enormous entropy production. In the present work, we look for the effects of Lorentz invariance violation (LIV) in flat and curved backgrounds that can be measured by quantum entanglement and quantum thermodynamic entropies for scalar modes. Our results show that the general behavior of these entropies is the same. We also consider variations of the entropies with respect to LIV and cosmological and field parameters. Using the properties of these entropies, along with detecting the most entangled modes, we extract information about the past existence of LIV, which in turn might be useful in recovering the quantum structure of gravity. Indeed, the occurrence of a peak in the behavior of these entropies for a specific momentum could provide information about the expansion parameters. Moreover, information about the LIV parameter is codified in this peak.

We provide a compact and unified treatment of power spectrum observables for the effective field theory (EFT) of inflation with the complete set of operators that lead to second-order equations of motion in metric perturbations in both space and time derivatives, including Horndeski and Gleyzes-Langlois-Piazza-Vernizzi theories. We relate the EFT operators in ADM form to the four additional free functions of time in the scalar and tensor equations. Using the generalized slow-roll formalism, we show that each power spectrum can be described by an integral over a single source that is a function of its respective sound horizon. With this correspondence, existing model independent constraints on the source function can be simply reinterpreted in the more general inflationary context. By expanding these sources around an optimized freeze-out epoch, we also provide characterizations of these spectra in terms of five slow-roll hierarchies whose leading-order forms are compact and accurate as long as EFT coefficients vary only on time scales greater than an $e$-fold. We also clarify the relationship between the unitary gauge observables employed in the EFT and the comoving gauge observables of the postinflationary universe.

A phenomenological study of the final combined HERA data on inclusive deep inelastic scattering has been performed. The data are presented and investigated for a kinematic range extending from values of the four-momentum transfer, $Q^2$, above $10^4{\mathrm{GeV}}^2$ down to the lowest values observable at HERA of $Q^2=0.045{\mathrm{GeV}}^2$ and Bjorken $x$, $x_{\text{Bj}}=6\times {10}^{-7}$. The data are well described by fits based on perturbative quantum chromodynamics (QCD) using collinear factorisation and evolution of the parton densities encompassed in the Dokshitzer-Gribov-Lipatov-Altarelli-Parisi formalism from the highest $Q^2$ down to $Q^2$ of a few ${\mathrm{GeV}}^2$. The Regge formalism with the soft Pomeron pole can describe the data up to $Q^2\approx 0.65{\mathrm{GeV}}^2$. The complete data set can be described by a new fit using the Abramowicz-Levin-Levy-Maor parametrization. The region between the Regge and the perturbative QCD regimes is of particular interest.

We report on a new mechanism that leads to the generation of primordial chiral gravitational waves, and hence, the violation of the parity symmetry in the Universe. We show that nonperturbative production of fermions with a definite helicity is accompanied by the generation of chiral gravitational waves. This is a generic and model-independent phenomenon that can occur during inflation, reheating and radiation eras, and can leave imprints in the cosmic microwave background polarization and may be observed in future ground- and space-based interferometers. We also discuss a specific model where chiral gravitational waves are generated via the production of light chiral fermions during pseudoscalar inflation.

We show that the $C{P}^N$ model with an odd number of scalar fields and a $\mathsf{V}$-shaped potential possesses some finite energy compact solutions in the form of $Q$-balls and $Q$-shells. Such solutions were obtained in $3+1$ dimensions. The $Q$-balls appear for $N=1$ and $N=3$, whereas the $Q$-shells are present for higher odd numbers $N$. We show that the energy of the solutions behaves as $E\sim |Q{|}^{5/6}$, where $Q$ stands for the Noether charge.