The mixing of $S\mathrm{\text{−}}D$ partial waves for the heavy meson pairs in the decays ${\rm Y}(5S)\to [B^{*}\overline{B}+\mathrm{c}.\mathrm{c}.]\pi$ and ${\rm Y}(5S)\to B^{*}{\overline{B}}^{*}\pi$ is considered. It is argued that this mixing, enhanced by the heavy meson mass, is calculable as dominated by a rescattering through pion exchange if the production of the heavy mesons is dominated by $S$-wave “molecular” resonances $Z_b(10610)$ and $Z_b(10650)$. The effect of the mixing grows with the c.m. energy $E$ in each channel over the threshold, and may reach $10÷20\%$ in the rate at the upper end of applicability of the discussed approach, $E\sim 15\mathrm{MeV}$. It is also argued that the mixing is likely to reach maximum at an energy approximately equal to the mass gap between the thresholds.

The BABAR measurements of the ratios $\mathcal{R}(D^{(*)})=\frac{\mathcal{B}(B\to D^{(*)}\tau {\overline{\nu }}_{\tau })}{\mathcal{B}(B\to D^{(*)}\mu {\overline{\nu }}_{\mu })}$ deviate from the standard model expectation, while new results on the purely leptonic $B\to \tau {\overline{\nu }}_{\tau }$ mode show a better consistency with the standard model, within the uncertainties. In a new physics scenario, one possibility to accommodate these two experimental facts consists in considering an additional tensor operator in the effective weak Hamiltonian. We study the effects of such an operator in a set of observables, in semileptonic $B\to D^{(*)}$ modes as well as in semileptonic $B$ and $B_s$ decays to excited positive-parity charmed mesons.

We perform a study of the flavor evolution in the early universe of a multiflavor active-sterile neutrino system with parameters inspired by the short-baseline neutrino anomalies. In a neutrino-symmetric bath a “thermal” population of the sterile state would quickly grow, but in the presence of primordial neutrino asymmetries a self-suppression as well as a resonant sterile neutrino production can take place, depending on temperature and chosen parameters. In order to characterize these effects, we go beyond the usual average momentum and single-mixing approximations and consider a multimomentum and multiflavor treatment of the kinetic equations. We find that the enhancement obtained in this case with respect to the average momentum approximation is significant, up to $\sim 20\%$ of a degree of freedom. Such a detailed and computationally demanding treatment further raises the asymmetry values required to significantly suppress the sterile neutrino production, up to $|L_{\nu }|\gtrsim \mathcal{O}({10}^{-2})$. For such asymmetries, however, the active-sterile flavor conversions happen so late that significant distortions are produced in the electron (anti)neutrino spectra. The larger $|L_{\nu }|$, the more the impact of these distortions takes over as a dominant cosmological effect, notably increasing the ${}^4\mathrm{He}$ abundance in primordial nucleosynthesis. The standard expression of the primordial yields in terms of the effective number of neutrinos and asymmetries is also greatly altered. We numerically estimate the magnitude of such effects for a few representative cases and comment on the implications for current cosmological measurements.

The inert doublet dark matter model has recently gained attention as a possible means of facilitating a strongly first-order electroweak phase transition (EWPT), as needed for baryogenesis. We extend previous results by considering the regime where the DM is heavier than half the Higgs mass, and its relic density is determined by annihilation into $W$, $Z$ and Higgs bosons. We find a large natural region of parameter space where the EWPT is strongly first order, while the lightest inert doublet state typically contributes only 0.1%–3% of the total dark matter. Despite this small density, its interactions with nucleons are strong enough to be directly detectable given a factor of 5 improvement over the current sensitivity of XENON100. A 10% increase in the branching ratio for Higgs decays to two photons is predicted.

Using the method of uniqueness a two-loop massless propagator Feynman diagram with a noninteger index on the central line is evaluated in a very transparent way. The result is applied to the computation of the two-loop polarization operator in reduced quantum electrodynamics.

We consider radially twisted nanotubes in the low-energy approximation, where the dynamics is governed by a one-dimensional Dirac equation. The mechanical deformation of the nanotubes is reflected by the presence of an effective vector potential. We discuss twisted carbon and boron-nitride nanotubes, where deformations give rise to periodic and nonperiodic finite-gap Hamiltonians. The intimate relation of these systems with the integrable Ablowitz-Kaup-Newell-Segur hierarchy is exploited in the study of their spectral properties as well as in the computation of the (local) density of states. We show that a nonlinear hidden supersymmetry generated by local supercharges arises naturally in the finite-gap configurations of twisted nanotubes with time-reversal symmetry. The properties of the van Hove singularities are encoded in its structure.

The quark mass dependences of light-element binding energies and nuclear scattering lengths are derived using chiral perturbation theory in combination with nonperturbative methods. In particular, we present new, improved values for the quark mass dependence of meson resonances that enter the nuclear force. A detailed analysis of the theoretical uncertainties arising in this determination is presented. As an application, we derive from a comparison of observed and calculated primordial deuterium and helium abundances a stringent limit on the variation of the light quark mass, $\delta m_q/m_q=0.02\pm 0.04$. Inclusion of the neutron lifetime modification, under the assumption of a variation of the Higgs vacuum expectation value that translates into changing quark, electron, and weak gauge boson masses, leads to a stronger limit, $|\delta m_q/m_q|<0.009$.

We study the renormalization of some dimension-4, 7 and 10 operators in a class of nonlinear scalar-tensor theories. These theories are invariant under (a) linear diffeomorphisms which represent an exact symmetry of the full nonlinear action, and (b) global field-space Galilean transformations of the scalar field. The Lagrangian contains a set of nontopological interaction terms of the above-mentioned dimensionality, which we show are not renormalized at any order in perturbation theory. We also discuss the renormalization of other operators, that may be generated by loops and/or receive loop corrections, and identify the regime in which they are subleading with respect to the operators that do not get renormalized. Interestingly, such scalar-tensor theories emerge in a certain high-energy limit of the ghost-free theory of massive gravity. One can use the nonrenormalization properties of the high-energy limit to estimate the magnitude of quantum corrections in the full theory. We show that the quantum corrections to the three free parameters of the model, one of them being the graviton mass, are strongly suppressed. In particular, we show that having an arbitrarily small graviton mass is technically natural.

We present results from an extensive study of 88 precessing, equal-mass black-hole binaries with large spins (83 with intrinsic spins $|{\overrightarrow{S}}_i/m_i^2|$ of 0.8 and 5 with intrinsic spins of 0.9), and use these data to model new nonlinear contributions to the gravitational recoil imparted to the merged black hole. We find a new effect, the cross kick, that enhances the recoil for partially aligned binaries beyond the hangup kick effect. This has the consequence of increasing the probabilities of recoils larger than $2000\mathrm{km}{\mathrm{s}}^{-1}$ by nearly a factor of 2, and consequently, of black holes getting ejected from galaxies, as well as the observation of large differential redshifts/blueshifts in the cores of recently merged galaxies.

The usual (type A) thin-wall Coleman—de Luccia instanton is made by a bigger-than-half sphere of the false vacuum and a smaller-than-half sphere of the true vacuum. It has the standard $O(4)$ symmetric negative mode associated with changing the size of the true vacuum region. On the other hand, the type B instanton, made by two smaller-than-half spheres, was believed to have lost this negative mode. We argue that such a belief is misguided due to an overrestriction on the Euclidean path integral. We introduce the idea of a “purely geometric junction” to visualize why such a restriction could be removed, and then we explicitly construct this negative mode. We also show that type B and type A instantons have the same thermal interpretation for mediating tunnelings.

The evolution of the curvature perturbation after multifield inflation is studied in the light of the curvaton mechanism. Past numerical studies show that many-field inflation causes significant evolution of the curvature perturbation after inflation, which generates significant non-Gaussianity at the same time. We reveal the underlying mechanism of the evolution and show that the evolution is possible in a typical two-field inflation model.

Photons can gravitationally scatter off a cosmic string loop and gain or lose energy. We consider the spectral distortion induced by cosmic string loops placed in an ambient thermal bath of photons. The fractional deviation from a thermal spectrum caused by cosmic strings is estimated to scale as $(G_{\mathrm{N}}\mu {)}^2{z}^2$, where $G_{\mathrm{N}}$ is Newton’s constant, $\mu$ is the string tension, and $z$ is the cosmological redshift after which spectral distortions can survive. This effect is large enough to potentially be of observational interest.

A typesetting mistake in Eq. (25) is corrected. The numerical analysis and the conclusions remain unchanged.

We illustrate how the matrix element method at next-to-leading order can be used to discriminate between events arising from the production of a Higgs boson, which subsequently decays to a final state consisting of ${\ell }^{+}{\ell }^{-}\gamma$, and the background production of the same final state. We illustrate how the method could be used in an experimental analysis by devising cuts on the signal ($P_S$) and background ($P_B$) weights that are computed event by event in this approach. We find that we can increase the $S/\sqrt{B}$ ratio by around 50% compared to an invariant mass fit on its own. Considering only statistical uncertainty, this is equivalent to recording a factor of around two times more integrated luminosity.

In the Aharony-Bergman-Jafferis-Maldacena model, we study the three-point function of two heavy operators and an (ir)relevant one. Following the AdS/CFT correspondence, the structure constant in the large ’t Hooft coupling limit can be factorized into two parts. One is the structure constant with a marginal operator, which is fully determined by the physical quantities of heavy operators and gives rise to a result that is consistent with the renormalization-group analysis. The other can be expressed as the universal form depending only on the conformal dimension of an (ir)relevant operator. We also investigate the new size effect of a circular string dual to a certain closed spin chain.

We formulate a theory of an interacting scalar field on the fuzzy sphere as a random matrix model. We then analyze the expectation values of observables of the theory in the large $N$ limit, and we demonstrate that the eigenvalue distribution of the matrix $M$ remains the polynomially deformed Wigner semicircle. We also compute distributions involving the matrix Laplacian of $M$, and we show that the correlation between the eigenvalues of these two is different from the free field case.

A procedure to define the Becchi-Rouet-Stora-Tyutin (BRST) charge from the Noether one in extended phase space is given. It is outlined how this prescription can be applied to a Friedmann-Robertson-Walker space-time with a differential gauge condition and it allows us to reproduce the results of Ref. [21]. Then, we discuss the cohomological classes associated with functions in extended phase space having ghost number one and we recover the frozen formalism for classical observables. Finally, we consider the quantization of Becchi-Rouet-Stora-Tyutin–closed states and we define a scalar product which implements the super-Hamiltonian constraint.

The spatially flat and isotropic cosmological model of Brans-Dicke theory with coupling parameter $\omega \ne -\frac{3}{2}$ is quantized by the approach of loop quantum cosmology. An interesting feature of this model is that although the Brans-Dicke scalar field is nonminimally coupled with curvature, it can still play the role of an emergent time variable. In the quantum theory, the classical differential equation which represents cosmological evolution is replaced by a quantum difference equation. The effective Hamiltonian and modified dynamical equations of loop quantum Brans-Dicke cosmology are also obtained, which lay a foundation for the phenomenological investigation to possible quantum gravity effects in cosmology. The effective equations indicate that the classical big bang singularity is again replaced by a quantum bounce in loop quantum Brans-Dicke cosmology.

Several approaches to the quantum-gravity problem predict that spacetime should be “fuzzy,” but so far these approaches have been unable to provide a crisp physical characterization of this notion. An intuitive picture of spacetime fuzziness has been proposed on the basis of semiheuristic arguments and, in particular, involves an irreducible Planck-scale contribution to the uncertainty of the energy of a particle. These arguments also inspired a rather active phenomenological program that looks for the blurring of images of distant astrophysical sources that would result from such energy uncertainties. Here we report the first ever physical characterization of spacetime fuzziness derived constructively within a quantum picture of spacetime, the one provided by spacetime noncommutativity. Our results confirm earlier heuristic arguments suggesting that spacetime fuzziness, while irrelevantly small on terrestrial scales, could be observably large for propagation of particles over cosmological distances. However, we find no Planck-scale-induced lower bound on the uncertainty of the energy of particles; we observe that this changes how we should picture a quantum spacetime, and it also imposes a reanalysis of the associated phenomenology.

The present article discusses the effect of a Lee-Wick partner infested radiation phase of the early universe. As Lee-Wick partners can contribute negative energy density it is always possible that at some early phase of the universe when the Lee-Wick partners were thermalized the total energy density of the universe became very small making the effective Hubble radius very big. This possibility gives rise to the probability of a bouncing universe. As will be shown in the article a simple Lee-Wick radiation is not enough to produce a bounce. There can be two possibilities which can produce a bounce in the Lee-Wick radiation phase. One requires a cold dark matter candidate to trigger the bounce and the other possibility requires the bouncing temperature to be fine-tuned such as all the Lee-Wick partners of the standard fields are not thermalized at the bounce temperature. Both the possibilities give rise to a blue-tilted power spectrum of metric perturbations. Moreover the bouncing universe model can predict the lower limit of the masses of the Lee-Wick partners of chiral fermions and massless gauge bosons. The mass limit intrinsically depends upon the bounce temperature.