The spectrum of the massive $CPT$-odd Yang-Mills propagator with Lorentz violation is calculated at tree level. The modification is due to mass terms generated by the exigence of multiplicative renormalizability of Yang-Mills theory with Lorentz violation. The causality analysis is performed with group and front velocities for both spacelike and timelike background tensors. It is shown that, by demanding causality, it is always possible to define a physical sector for the gauge propagator. Hence, it is expected that the model is also unitary if one takes the Faddeev-Popov ghost into account.

In manifolds with spatial boundary, BRST formalism can be used to quantize gauge theories. We show that, in a $U(1)$ gauge theory, only a subset of all the boundary conditions allowed by the self-adjointness of the Hamiltonian preserves BRST symmetry. Hence, the theory can be quantized using BRST formalism only when that subset of boundary conditions is considered. We also show that for such boundary conditions, there exist fermionic states which are localized near the boundary.

We study here a complete quantization of a Callan-Giddings-Harvey-Strominger vacuum model following loop quantum gravity techniques. Concretely, we adopt a formulation of the model in terms of a set of new variables that resemble the ones commonly employed in spherically symmetric loop quantum gravity. The classical theory consists of two pairs of canonical variables plus a scalar and diffeomorphism (first class) constraints. We consider a suitable redefinition of the Hamiltonian constraint such that the new constraint algebra (with structure constants) is well adapted to the Dirac quantization approach. For it, we adopt a polymeric representation for both the geometry and the dilaton field. On the one hand, we find a suitable invariant domain of the scalar constraint operator, and we construct explicitly its solution space. There, the eigenvalues of the dilaton and the metric operators cannot vanish locally, allowing us to conclude that singular geometries are ruled out in the quantum theory. On the other hand, the physical Hilbert space is constructed out of them, after group averaging the previous states with the diffeomorphism constraint. In turn, we identify the standard observable corresponding to the mass of the black hole at the boundary, in agreement with the classical theory. We also construct an additional observable on the bulk associated with the square of the dilaton field, with no direct classical analog.

We study numerically in the time domain the linearized gravitational waves emitted from a plunge into a nearly extremal Kerr black hole by solving the inhomogeneous Teukolsky equation. We consider spinning black holes for which the specific spin angular momentum $a/M=1-\epsilon$, and we consider values of $\epsilon \ge {10}^{-6}$. We find an effective transient behavior for the quasinormal ringdown: the early phase of the quasinormal ringdown is governed by a decay according to inverse time, with frequency equaling twice the black hole’s horizon frequency. The smaller $\epsilon$ is, the later the transition from this transient inverse-time decay to exponential decay. Such sources, if they exist, may be interesting potential sources for terrestrial or space-borne gravitational-wave observatories.

In this paper, using the general Schwinger-DeWitt approach, we construct the approximate stress-energy tensor of the quantized massive scalar field with arbitrary curvature coupling in $D=4$ and $D=5$ classical spacetimes of the electrically charged static black holes with the cosmological constant. Depending on the sign of the cosmological constant we consider both spherically symmetric and topological spacetimes with the special emphasis put on the extremal and ultraextremal configurations. Moreover, we analyze the geometries of the closest vicinity of the degenerate horizons, which topologically are the product of the maximally symmetric subspaces. We solve the semiclassical Einstein field equations for such product spacetimes. Since the transformation $k\to -k$ and $f^{\prime \prime }\to -f^{\prime \prime }$ leaves the equations unchanged, where $k$ is the curvature of the ($D-2$)-dimensional subspace and $f^{\prime \prime }$ is the second derivative of the metric potential at the degenerate horizon, it suffices to consider only the spherically symmetric case. It is shown that in four and five dimensions there are forbidden sectors of the parameter space.

In this work, we extend the so-called typicality approach, originally formulated in statistical mechanics contexts, to $SU(2)$-invariant spin-network states. Our results do not depend on the physical interpretation of the spin network; however, they are mainly motivated by the fact that spin-network states can describe states of quantum geometry, providing a gauge-invariant basis for the kinematical Hilbert space of several background-independent approaches to quantum gravity. The first result is, by itself, the existence of a regime in which we show the emergence of a typical state. We interpret this as the proof that in that regime there are certain (local) properties of quantum geometry which are “universal.” Such a set of properties is heralded by the typical state, of which we give the explicit form. This is our second result. In the end, we study some interesting properties of the typical state, proving that the area law for the entropy of a surface must be satisfied at the local level, up to logarithmic corrections which we are able to bound.

We consider reheating in a class of asymptotically safe quantum field theories recently studied in [D. F. Litim and F. Sannino, Asymptotic safety guaranteed, J. High Energy Phys. 12 (2014) 178; D. F. Litim, M. Mojaza, and F. Sannino, Vacuum stability of asymptotically safe gauge-Yukawa theories, J. High Energy Phys. 01 (2016) 081]. These theories allow for an inflationary phase in the very early universe. Inflation ends with a period of reheating. Since the models contain many scalar fields which are intrinsically coupled to the inflaton there is the possibility of parametric resonance instability in the production of these fields, and the danger that the induced curvature fluctuations will become too large. Here we show that the parametric instability indeed arises, and that hence the energy transfer from the inflaton condensate to fluctuating fields is rapid. Demanding that the curvature fluctuations induced by the parametrically amplified entropy modes do not exceed the upper observational bounds puts a lower bound on the number of fields which the model followed in [D. F. Litim and F. Sannino, Asymptotic safety guaranteed, J. High Energy Phys. 12 (2014) 178; D. F. Litim, M. Mojaza, and F. Sannino, Vacuum stability of asymptotically safe gauge-Yukawa theories, J. High Energy Phys. 01 (2016) 081] must contain. This bound also depends on the total number of $e$-foldings of the inflationary phase.

We present a new, semianalytic framework for estimating the level of residuals present in cosmic microwave background (CMB) maps derived from multifrequency CMB data and forecasting their impact on cosmological parameters. The data are assumed to contain non-negligible signals of astrophysical and/or Galactic origin, which we clean using a parametric component separation technique. We account for discrepancies between the foreground model assumed during the separation procedure and the true one, allowing for differences in scaling laws and/or their spatial variations. Our estimates and their uncertainties include both systematic and statistical effects and are averaged over the instrumental noise and CMB signal realizations. The framework can be further extended to account self-consistently for existing uncertainties in the foreground models. We demonstrate and validate the framework on simple study cases which aim at estimating the tensor-to-scalar ratio, $r$. The proposed approach is computationally efficient permitting an investigation of hundreds of setups and foreground models on a single CPU.

We report a measurement of the ionization efficiency of silicon nuclei recoiling with sub-keV kinetic energy in the bulk silicon of a charge-coupled device (CCD). Nuclear recoils are produced by low-energy neutrons ($<24\mathrm{keV}$) from a ${}^{124}\mathrm{Sb}\text{−}{}^9\mathrm{Be}$ photoneutron source, and their ionization signal is measured down to 60 eV electron equivalent. This energy range, previously unexplored, is relevant for the detection of low-mass dark matter particles. The measured efficiency is found to deviate from the extrapolation to low energies of the Lindhard model. This measurement also demonstrates the sensitivity to nuclear recoils of CCDs employed by DAMIC, a dark matter direct detection experiment located in the SNOLAB underground laboratory.

We present results of a dark matter search performed with a 0.6 kg d exposure of the DAMIC experiment at the SNOLAB underground laboratory. We measure the energy spectrum of ionization events in the bulk silicon of charge-coupled devices down to a signal of 60 eV electron equivalent. The data are consistent with radiogenic backgrounds, and constraints on the spin-independent WIMP-nucleon elastic-scattering cross section are accordingly placed. A region of parameter space relevant to the potential signal from the CDMS-II Si experiment is excluded using the same target for the first time. This result obtained with a limited exposure demonstrates the potential to explore the low-mass WIMP region ($<10\mathrm{GeV}{c}^{-2}$) with the upcoming DAMIC100, a 100 g detector currently being installed in SNOLAB.

The fluctuation-dissipation theorem states that each source of dissipation yields corresponding fluctuations. The most obvious source of dissipation in liquids is viscosity—internal friction between layers of matter. However, this property also exists in solid materials in a glass state, i.e., an amorphous substance that cannot become a crystal due to high viscosity. Fused silica is a low-loss glass material used in many interferometric applications demanding high stability, such as Fabry-Perot etalons and gravitational-wave detector mirrors and suspensions. Very high viscosity (from $10^{17}$ to $10^{40}\mathrm{Pa}\mathrm{s}$ in the literature) can be the source of additional noise and can influence the performance of such devices. We show that fused silica may be described with the standard linear solid model of viscoelastisity and present a method to estimate this type of noise.

We study the well-known Friedrichs model, in which a discrete state is coupled to a continuum state. By examining the pole behaviors of the Friedrichs model in a specific form factor thoroughly, we find that, in general, when the bare discrete state is below the threshold of the continuum state, there should also be a virtual-state pole accompanying the bound-state pole originating from the bare discrete state as the coupling is turned on. There are also other second-sheet poles originating from the singularities of the form factor. We give a general argument for the existence of these two kinds of states. As the coupling is increased to a certain value, the second-sheet poles may merge and become higher-order poles. We then discuss the completeness relations incorporating bound states, virtual states, and resonant states corresponding to higher-order poles.

We revisit a set of dark sector models, motivated by anomalies observed in $B$ decays and the muon anomalous magnetic moment, in the light of a recently reported diphoton excess around 750 GeV. Interpreting the excess as a scalar resonance associated with the symmetry breaking sector of a dark gauge group, we show that a diphoton cross section of $\mathcal{O}(\mathrm{fb})$ can be accommodated, together with anomalies in $R_K$ and $g_{\mu }-2$ within a minimal dark sector model. The resulting prominent collider signatures are in the form of wide resonant signals into top and muon pair final states below $\sim 1\mathrm{TeV}$. The model further predicts a dark matter candidate, yet with a significantly underabundant relic density, unless produced by an appropriate nonthermal mechanism.

Supersymmetric $SO(10)$ grand unified models with renormalizable Yukawa couplings involving only $\mathbf{10}$ and $\overline{\mathbf{126}}$ Higgs fields have been shown to realize the fermion masses and mixings economically. In previous works, the sum rule of the fermion mass matrices is given by inputting the quark matrices, and the neutrino mixings are predicted in this framework. Now the three neutrino mixings have been measured, and in this paper, we give the sum rule by inputting the lepton mass matrices, which makes clear certain features of the solution, especially if the vacuum expectation values of $\mathbf{126}+\overline{\mathbf{126}}$ ($v_R$) are large and the right-handed neutrinos are heavy. We perform the ${\chi }^2$ analyses to fit the fermion masses and mixings using the sum rule. In previous works, the best fit appears at $v_R\sim 10^{13}\mathrm{GeV}$, and the fit at the large $v_R$ scale ($\sim 10^{16}\mathrm{GeV}$) has been less investigated. Our expression of the sum rule has a benefit to understand the flavor structure in the large $v_R$ solution. Using the fit results, we perform the calculation of the $\mu \to e\gamma$ process and the electric dipole moment of electron, and the importance of $v_R$ dependence emerges in low energy phenomena. We also show the prediction of the $CP$ phase in the neutrino oscillations, which can be tested in the near future.

The rare decay $h\to \mathrm{\Upsilon }\gamma$ has a very small rate in the Standard Model, due to a strong cancellation between the direct and indirect diagrams. Models with a changed $hbb$ coupling can thus lead to a great increase in this decay. Current limits on two Higgs doublet models still allow for the possibility that the $hbb$ coupling might have a sign opposite to the Standard Model, the so-called “wrong-sign.” We show how $h\to \mathrm{\Upsilon }\gamma$ can be used to put limits on the wrong-sign solutions.

We study the $\overline{D}D$ (${\overline{D}}^0{D}^0$ and $D^{-}{D}^{+}$) charm meson pair production in antiproton ($\overline{p}$) induced reactions on nuclei at beam energies ranging from threshold to several GeV. Our model is based on an effective Lagrangian approach that has only the baryon-meson degrees of freedom and involves the physical hadron masses. The reaction proceeds via the $t$-channel exchanges of ${\mathrm{\Lambda }}_c^{+}$, ${\mathrm{\Sigma }}_c^{+}$, and ${\mathrm{\Sigma }}_c^{++}$ baryons in the initial collision of the antiproton with one of the protons of the target nucleus. The medium effects on the exchanged baryons are included by incorporating in the corresponding propagators, the effective charm baryon masses calculated within a quark-meson coupling (QMC) model. The wave functions of the bound proton have been determined within the QMC model as well as in a phenomenological model where they are obtained by solving the Dirac equation with appropriate scalar and vector potentials. The initial- and final-state distortion effects have been approximated by using an eikonal approximation-based procedure. Detailed numerical results are presented for total and double differential cross sections for the ${\overline{D}}^0{D}^0$ and $D^{-}{D}^{+}$ production reactions on ${}^{16}\mathrm{O}$ and ${}^{90}\mathrm{Zr}$ targets. It is noted that at $\overline{p}$ beam momenta of interest to the $\overline{\mathrm{P}}\mathrm{ANDA}$ experiment, medium effects lead to noticeable enhancements in the charm meson production cross sections.

We provide results for the open-flavor strong decays of strange and nonstrange baryons into a baryon-vector/pseudoscalar meson pair. The decay amplitudes are computed in the ${{}^{3}P}_0$ pair-creation model, where $s\overline{s}$ pair-creation suppression is included for the first time in the baryon sector, in combination with the $U(7)$ and hypercentral models. The effects of this $s\overline{s}$ suppression mechanism cannot be reabsorbed in a redefinition of the model parameters or in a different choice of the ${{}^{3}P}_0$ model vertex factor. Our results for the decay amplitudes are compared with the existing experimental data and previous ${{}^{3}P}_0$ and elementary meson emission model calculations. In this respect, we show that distinct quark models differ in the number of missing resonances they predict and also in the quantum numbers of states. Therefore, future experimental results will be important in order to disentangle different models of baryon structure. Finally, in the appendixes, we provide some details of our calculations, including the derivation of all relevant flavor couplings with strangeness suppression. This derivation may be helpful to calculate the open-flavor decay amplitudes starting from other models of baryons.

We have analyzed the singularities of a triangle loop integral in detail and derived a formula for an easy evaluation of the triangle singularity on the physical boundary. It is applied to the ${\mathrm{\Lambda }}_b\to J/\psi K^{-}p$ process via ${\mathrm{\Lambda }}^{*}$-charmonium-proton intermediate states. Although the evaluation of absolute rates is not possible, we identify the ${\chi }_{c1}$ and the $\psi (2S)$ as the relatively most relevant states among all possible charmonia up to the $\psi (2S)$. The $\mathrm{\Lambda }(1890){\chi }_{c1}p$ loop is very special, as its normal threshold and triangle singularities merge at about 4.45 GeV, generating a narrow and prominent peak in the amplitude in the case that the ${\chi }_{c1}p$ is in an $S$ wave. We also see that loops with the same charmonium and other ${\mathrm{\Lambda }}^{*}$ hyperons produce less dramatic peaks from the threshold singularity alone. For the case of ${\chi }_{c1}p\to J/\psi p$ and quantum numbers $3/2^{-}$ or $5/2^{+}$, one needs $P$ and $D$ waves, respectively, in the ${\chi }_{c1}p$, which drastically reduce the strength of the contribution and smooth the threshold peak. In this case, we conclude that the singularities cannot account for the observed narrow peak. In the case of $1/2^{+}$, $3/2^{+}$ quantum numbers, where ${\chi }_{c1}p\to J/\psi p$ can proceed in an $S$ wave, the $\mathrm{\Lambda }(1890){\chi }_{c1}p$ triangle diagram could play an important role, though neither can assert their strength without further input from experiments and lattice QCD calculations.

We present the nuclear transverse momentum broadening for Drell-Yan lepton pair production in $p+A$ collisions at next-to-leading order in powers of strong coupling constant ${\alpha }_s$. We verify that the transverse-momentum-weighted differential cross section in next-to-leading order perturbative QCD at twist 4 can be factorized into the convolution of the parton distribution function of an active parton in the projectile proton, a twist-4 multiparton correlation function of the target nucleus, and a perturbatively calculable hard coefficient function. We identify a QCD evolution equation for such a twist-4 nuclear gluon-quark correlation function and verify its universality—its process independence. This finding demonstrates the prediction power of the perturbative QCD factorization approach for studying parton multiple scattering in the nuclear medium.

We report a measurement of the ratio $\mathcal{R}(D^{*})=\mathcal{B}({\overline{B}}^0\to D^{*+}{\tau }^{-}{\overline{\nu }}_{\tau })/\mathcal{B}({\overline{B}}^0\to D^{*+}{\ell }^{-}{\overline{\nu }}_{\ell })$, where $\ell$ denotes an electron or a muon. The results are based on a data sample containing $772\times 10^{6}B\overline{B}$ pairs recorded at the $\mathrm{\Upsilon }(4S)$ resonance with the Belle detector at the KEKB $e^{+}{e}^{-}$ collider. We select a sample of $B^0{\overline{B}}^0$ pairs by reconstructing both $B$ mesons in semileptonic decays to $D^{*\mp }{\ell }^{\pm }$. We measure $\mathcal{R}(D^{*})=0.302\pm 0.030(\text{stat})\pm 0.011(\text{syst})$, which is within $1.6\sigma$ of the Standard Model theoretical expectation, where the standard deviation $\sigma$ includes systematic uncertainties. We use this measurement to constrain several scenarios of new physics in a model-independent approach.