We study the finite-volume correction on the hadronic vacuum polarization contribution to the muon $g-2$ ($a_{\mu }^{\mathrm{hvp}}$) in lattice QCD at (near) physical pion mass using two different volumes: $(5.4\mathrm{fm}{)}^4$ and $(8.1\mathrm{fm}{)}^4$. We use an optimized AMA technique for noise reduction on $N_f=2+1$ PACS gauge configurations with stout-smeared clover-Wilson fermion action and Iwasaki gauge action at a single lattice cut-off $a^{-1}=2.33\mathrm{GeV}$. The calculation is performed for the quark-connected light-quark contribution in the isospin symmetric limit. We take into account the effects of backward state propagation by extending a temporal boundary condition. In addition, we study a quark-mass correction to tune to the exact same physical pion mass on different volume and compare those correction with chiral perturbation. We find $10(26)\times {10}^{-10}$ difference for light quark $a_{\mu }^{\mathrm{hvp}}$ between $(5.4\mathrm{fm}{)}^4$ and $(8.1\mathrm{fm}{)}^4$ lattice in 146 MeV pion.

Recently, transport coefficients, viz., shear viscosity, electrical conductivity, etc., of strongly interacting matter produced in heavy-ion collisions have drawn considerable interest. We study the normalized electrical conductivity (${\sigma }_{\mathrm{el}}/\mathrm{T}$) of hot QCD matter as a function of temperature (T) using the color string percolation model (CSPM). We also study the temperature dependence of shear viscosity and its ratio with electrical conductivity for the QCD matter. We compare CSPM estimations with various existing results and lattice QCD predictions with ($2+1$) dynamical flavors. We find that ${\sigma }_{\mathrm{el}}/\mathrm{T}$ in CSPM has a very weak dependence on the temperature. We compare CSPM results with those obtained in the Boltzmann approach to multiparton scatterings model. A good agreement is found between CSPM results and predictions of the Boltzmann approach to multiparton scatterings with a fixed strong coupling constant.

We investigate the mass spectra of the lowest-lying singly heavy baryons, based on the self-consistent chiral quark-soliton model. We take into account the rotational $1/N_c$ and strange current quark mass ($m_{\mathrm{s}}$) corrections. Regarding $m_{\mathrm{s}}$ as a small perturbation, we expand the effective chiral action to the second order with respect to $m_s$. The mass spectra of heavy baryons are computed and compared with the experimental data. Fitting the classical masses of the heavy baryon to the center mass of each representation, we determine the masses of all the lowest-lying singly heavy baryons. We predict the mass of the ${\mathrm{\Omega }}_b^{*}$ baryon to be 6081.9 MeV, when the second-order $m_{\mathrm{s}}$ corrections are included.

Using CLEO-c data, we confirm the observation of $D^0\to \omega \eta$ by BESIII. In the Dalitz plot of $D^0\to K_S^0\eta {\pi }^0$, we find a background in the $K_S^0(\to {\pi }^{+}{\pi }^{-}){\pi }^0$ projection with a $m({\pi }^{+}{\pi }^{-}{\pi }^0)$ equal to the $\omega (782)$ mass. In a direct search for $D^0\to \omega \eta$ we find a clear signal and measure ${\mathcal{B}\mathcal{F}}_{D^0\to \omega \eta }=(1.78\pm 0.19\pm 0.15)\times {10}^{-3}$, in good agreement with BESIII.

Motivated by recent results on small and hollow magnetic monopoles and on core and shell bimagnetic nanoparticles, we propose the construction of bimagnetic monopoles, which are structures that accommodate a magnetic monopole inside another magnetic monopole.

We work in the Heisenberg picture to demonstrate the classical-quantum correspondence (CQC) in which the dynamics of a quantum variable is equivalent to that of a complexified classical variable. The correspondence provides a tool for analyzing quantum backreaction problems which we illustrate by a toy model in which a rolling particle slows down due to quantum radiation. The dynamics found using the CQC is in excellent agreement with that found using the much more laborious full quantum analysis.

In theories with derivative (self-)interactions, the propagation of perturbations on nontrivial field configurations is determined by effective metrics. Generalized scalar-tensor theories belong in this class and this implies that the matter fields and gravitational perturbations do not necessarily experience the same causal structure. Motivated by this, we explore the causal structure of black holes as perceived by scalar fields in the Horndeski class. We consider linearized perturbations on a fixed background metric that describes a generic black hole. The effective metric that determines the propagation of these perturbations does not generally coincide with the background metric (to which matter fields couple minimally). Assuming that the metric and the scalar respect stationarity and that the surface gravity of the horizon is constant, we prove that Killing horizons of the background metric are always Killing horizons of the effective metric as well. Hence, scalar perturbations cannot escape the region that matter fields perceive as the interior of the black hole. This result does not depend on asymptotics but only on local considerations and does not make any reference to no-hair theorems. We then demonstrate that, when one relaxes the stationarity assumption for the scalar, solutions where the horizons of the effective and the background metrics do not match can be found in the decoupling limit.

We discuss a class of teleparallel scalar-torsion theories of gravity, which is parametrized by five free functions of the scalar field. The theories are formulated covariantly using a flat, but nonvanishing spin connection. We show how the actions of different theories within this class are related via conformal transformations of the tetrad and redefinitions of the scalar field, and derive the corresponding transformation laws for the free function in the action. From these we construct a number of quantities which are invariant under these transformations, and use them to write the action and field equations in different conformal frames. These results generalize a similar formalism for scalar-tensor theories of gravity, where the invariants have been used to express observables independently of the conformal frame.

We consider Lorentz invariant scalar-tensor teleparallel gravity theories with a Lagrangian built from the torsion scalar, a scalar field, its kinetic term and a derivative coupling between the torsion and the scalar field. The field equations of the theory are derived and the relation between the spin connection and the antisymmetric part of the tetrad field equations is found explicitly, which is an important consistency result for Lorentz invariant teleparallel theories of gravity. Afterwards we study the behavior of this class of theories under conformal transformations and find that such transformations map different theories in this class onto each other.

We discuss the most general class of teleparallel scalar-torsion theories of gravity in their covariant formulation. The only restrictions we impose are the invariance of the action under diffeomorphisms and local Lorentz transformations, as well as vanishing direct coupling of the matter fields to the teleparallel spin connection. In this general setting we discuss the implications of local Lorentz invariance and diffeomorphism invariance and derive the general structure of the field equations. Further, we show how different theories of this class are related to each other by conformal transformations of the tetrad and redefinitions of the scalar field. We finally show how the formalism can be generalized to an arbitrary number of scalar fields, and provide a few examples.

The kinetic Sunyaev Zel’dovich (kSZ) effect, cosmic microwave background (CMB) anisotropies induced by scattering from free electrons in bulk motion, is a primary target of future CMB experiments. In addition to shedding light on the distribution of baryons and the details of the epoch of reionization, measurements of the kSZ effect have the potential to address fundamental questions about the structure and evolution of our Universe on the largest scales and at the earliest times. This potential is unlocked by combining measurements of small-scale CMB anisotropies with large-scale structure surveys, a technique known as kSZ tomography. Previous work established a quadratic estimator for the remote dipole field, the CMB dipole observed at different locations in the Universe, given a CMB map, and a redshift-binned map of large-scale structure. This previous work did not include gravitational lensing, redshift space distortions, or nonlinear evolution of structure. In this paper, we investigate how well the remote dipole field can be reconstructed in the presence of such effects by using mock data from a suite of simulations of gigaparsec-sized regions of the Universe. To properly model both large and small scales, we develop a novel box-in-box simulation pipeline, where small-scale information is obtained from L-PICOLA N-body simulations, and large-scale information obtained by evolving fields using linear theory and adding the resulting corrections to the N-body particle data. This pipeline allows us to create properly correlated maps of the primary CMB including lensing as well as the kSZ effect and density maps on the past light cone of an observer. Analyzing an ensemble of mocks, we find that the dipole field can be reconstructed with high fidelity over a range of angular scales and redshift bins. However, we present evidence for a bias due to the nonlinear evolution of structure. We also analyze correlations with the primary CMB, investigating the ability of kSZ tomography to reconstruct the intrinsic CMB dipole. Our results constitute a proof-of-principle that kSZ tomography is a promising technique for future data sets.

We develop a detailed anisotropic model for the astrophysical gravitational-wave background, including binary mergers of two stellar-mass black holes, two neutron stars, or one of each, which are expected to be the strongest contributions in the LIGO-Virgo frequency band. The angular spectrum of the anisotropies, quantified by the $C_{\ell }$ components, is calculated using two complementary approaches: (i) a simple, closed-form analytical expression, and (ii) a detailed numerical study using an all-sky mock light cone galaxy catalogue from the Millennium simulation. The two approaches are in excellent agreement at large angular scales, and differ by a factor of order unity at smaller scales. These anisotropies are considerably larger in amplitude than e.g., those in the temperature of the cosmic microwave background, confirming that it is important to model these anisotropies, and indicating that this is a promising avenue for future theoretical and observational work.

We consider the neutrino self-energy in a background composed of a scalar particle and a fermion using a simple model for the coupling of the form $\lambda {\overline{f}}_R{\nu }_L\varphi$. The results are useful in the context of dark matter-neutrino interaction models in which the scalar and/or fermion constitute the dark matter. The corresponding formulas for models in which the scalar particle couples to two neutrinos via a coupling of the form ${\lambda }^{(\nu \nu \varphi )}{\overline{\nu }}_R^c{\nu }_L\varphi$ are then obtained as a special case. In the presence of these interactions there can be new contributions to the neutrino effective potential and index of refraction in the context of neutrino collective oscillations in a supernova and in the early Universe hot plasma before neutrino decoupling. The formulas obtained here can be used to estimate those effects and/or put limits on the model parameters based on the contribution that such interactions can have in those contexts. A particular feature of the results is that the contribution to the neutrino self-energy or effective potential in a neutrino background due to the $\nu \nu \varphi$ coupling is proportional to the antineutrino-neutrino asymmetry $(n_{\overline{\nu }}-n_{\nu })$, in contrast to the standard $Z$ contribution which is proportional to $(n_{\nu }-n_{\overline{\nu }})$. Therefore the two contributions tend to cancel. If the cancellation is significant, it is conceivable that the $O(1/m_{\varphi }^4)$ terms give the dominant contribution. Alternatively, a limit can be set by requiring that the contribution of the $\nu \nu \varphi$ interaction to the neutrino effective potential does not cancel the standard contribution in an appreciable way.

We consider self-annihilation of dark matter, $\chi$, into metastable mediators, $Y$, and their subsequent decay into photons inside white dwarfs. We focus on reactions of the type $\chi \overline{\chi }\to YY$, where mediators, besides having a finite decay lifetime at rest ${\tau }_{\mathrm{rest}}\lesssim 1\mathrm{s}$, may suffer energy loss in the medium before they decay into photons, $Y\to \gamma \gamma$. We obtain attenuated gamma-ray luminosities arising from the combination of both effects. Using complementary sets of astrophysical measurements from cold white dwarfs in the M4 globular cluster as well as direct and indirect dark matter searches, we discuss further constraints on dark mediator lifetimes.

When looking for gravitational wave signals from known pulsars, targets have been treated using independent searches. Here we use a hierarchical Bayesian framework to combine observations from individual sources for two purposes: to produce a detection statistic for the whole ensemble of sources within a search, and to estimate the hyperparameters of the underlying distribution of pulsar ellipticities. Both purposes require us to assume some functional form of the ellipticity distribution, and as a proof of principle we take two toy distributions. One is an exponential distribution, defined by its mean, and the other is a half-Gaussian distribution defined by its width. We show that by incorporating a common parameterized prior ellipticity distribution we can be more efficient at detecting gravitational waves from the whole ensemble of sources than trying to combine observations with a simpler non-hierarchical method. This may allow us to detect gravitational waves from the ensemble before there is confident detection of any single source. We also apply this method using data for 92 pulsars from LIGO’s sixth science run. No evidence for a signal was seen, but 90% upper limits of $3.9\times {10}^{-8}$ and $4.7\times {10}^{-8}$ were set on the mean of an assumed exponential ellipticity distribution and the width of an assumed half-Gaussian ellipticity distribution, respectively.

We describe a systematic framework for periodic potentials of arbitrary dimension, such as those governing multiple axions. A novel type of alignment renders even complex theories analytically tractable. Theories with $\sim 100$ axions and random parameters have an exponential number of metastable vacua. Decay from a metastable minimum can occur via a thin-wall instanton and allows for a sufficient period of slow-roll inflation that ends in a vacuum containing axion dark matter and a cosmological constant, both consistent with current observations. Hence, this model can reproduce many macroscopic features of our Universe without tuned parameters.

We present a numerical study of the dynamical effects following a sudden change of the transverse trapping frequency in an elongated Bose-Einstein condensate, which induces periodic oscillations of the radial density. At early times, we observe an exponential growth of the number of resonant longitudinal phonons, in agreement with the predictions of the Bogoliubov–de Gennes treatment. We then observe an ordered sequence of phenomena induced by the nonlinearities of the system. The first is a loss of the nonseparability of the resonant phonon pairs. This is followed by the saturation of the exponential growth and a strong depletion of condensed atoms. Notably, these effects are well described by effective one-dimensional dynamics, and are hardly affected by the damping of the radial oscillations. Finally, the atomic spectrum becomes broad, featureless and almost incoherent, in agreement with experimental results. The link between this sequence of events and the preheating scenario in inflationary cosmology is striking, as is the similarity of techniques used to study them.

The discovery of doubly heavy baryon provides us with a new platform for precisely testing the standard model and searching for new physics. As a continuation of our previous works, we investigate the flavor-changing neutral current processes of doubly heavy baryons. The light-front approach is adopted to extract the form factors, in which the two spectator quarks are viewed as a diquark. Results for form factors are then used to predict some phenomenological observables, such as the decay width and the forward-backward asymmetry. We find that most of the branching ratios for $b\to s$ processes are ${10}^{-8}–{10}^{-7}$ and those for $b\to d$ processes are ${10}^{-9}–{10}^{-8}$. The flavor SU(3) symmetry and symmetry breaking effects are explored. Parametric uncertainties are also investigated.

The low-energy light-by-light cross section as determined by the nonlinear Euler-Heisenberg QED Lagrangian is evaluated in the presence of constant magnetic fields in the center-of-mass system of the colliding photons. This cross section has a complicated dependence on directions and polarizations. The overall magnitude decreases as the magnetic field is increased from zero, but this trend is reversed for ultrastrong magnetic fields $B\gtrsim B_c$, where the cross section eventually grows quadratically with the magnetic field strength perpendicular to the collision axis. This effect is due to interactions involving the lowest Landau level of virtual Dirac particles; it is absent in scalar QED. An even more dramatic effect is found for virtual charged vector mesons where the one-loop cross section diverges at the critical field strength due to an instability of the lowest Landau level and the possibility of the formation of a superconducting vacuum state. We also discuss (the absence of) implications for the recent observation of light-by-light scattering in heavy-ion collisions.

In this paper we consider an $S^1/{\mathbb{Z}}_2$ compactified flat extra dimensional scenario where all the standard model states can access the bulk and have generalized brane localized kinetic terms. The flavor structure of brane kinetic terms for the standard model fermions are dictated by stringent flavor bounds on the first two generations implying an $U(2{)}_{Q_L}\otimes U(2{)}_{u_R}\otimes U(2{)}_{d_R}$ flavor symmetry. We consider the constraints on such a scenario arising from dark matter relic density and direct detection measurements, precision electroweak data, Higgs physics, and LHC dilepton searches. We discuss the possibility of such a scenario providing an explanation of the recently measured anomaly in $R_{K^{(*)}}$ within the allowed region of the parameter space.