We describe a new analytical model for the accretion of particles from a rotating and charged spherical shell of dilute collisionless plasma onto a rotating and charged black hole. By assuming a continuous injection of particles at the spherical shell and by treating the black hole and a featureless accretion disk located in the equatorial plane as passive sinks of particles, we build a stationary accretion model. This may then serve as a toy model for plasma feeding an accretion disk around a charged and rotating black hole. Therefore, our new model is a direct generalization of the analytical accretion model introduced by E. Tejeda, P. A. Taylor, and J. C. Miller [Mon. Not. R. Astron. Soc. 429, 925 (2013)]. We use our generalized model to analyze the influence of a net charge of the black hole, which will in general be very small, on the accretion of plasma. Within the assumptions of our model we demonstrate that already a vanishingly small charge of the black hole may in general still have a non-negligible effect on the motion of the plasma, as long as the electromagnetic field of the plasma is still negligible. Furthermore, we argue that the inner and outer edges of the forming accretion disk strongly depend on the charge of the accreted plasma. The resulting possible configurations of accretion disks are analyzed in detail.

We report on the performance of the capacitive gap-sensing system of the Gravitational Reference Sensor on board the LISA Pathfinder spacecraft. From in-flight measurements, the system has demonstrated a performance, down to 1 mHz, that is ranging between 0.7 and $1.8\mathrm{aF}{\mathrm{Hz}}^{-1/2}$. That translates into a sensing noise of the test mass motion within 1.2 and $2.4\mathrm{nm}{\mathrm{Hz}}^{-1/2}$ in displacement and within 83 and $170\mathrm{nrad}{\mathrm{Hz}}^{-1/2}$ in rotation. This matches the performance goals for LISA Pathfinder, and it allows the successful implementation of the gravitational waves observatory LISA. A $1/f$ tail has been observed for frequencies below 1 mHz, the tail has been investigated in detail with dedicated in-flight measurements, and a model is presented in the paper. A projection of such noise to frequencies below 0.1 mHz shows that an improvement of performance at those frequencies is desirable for the next generation of gravitational reference sensors for space-borne gravitational waves observation.

We first report an axion haloscope search with toroidal geometry. In this pioneering search, we exclude the axion-photon coupling $g_{a\gamma \gamma }$ down to about $5\times {10}^{-8}{\mathrm{GeV}}^{-1}$ over the axion mass range from 24.7 to $29.1\mu \mathrm{eV}$ at a 95% confidence level. The prospects for axion dark matter searches with larger scale toroidal geometry are also considered.

Dynamical mechanisms to generate an ultralight axion of mass $\sim {10}^{-21}–{10}^{-22}\mathrm{eV}$ in supergravity and strings are discussed. An ultralight particle of this mass provides a candidate for dark matter that may play a role for cosmology at scales of 10 kpc or less. An effective operator approach for the axion mass provides a general framework for models of ultralight axions, and in one case recovers the scale ${10}^{-21}–{10}^{-22}\mathrm{eV}$ as the electroweak scale times the square of the hierarchy with an $O(1)$ Wilson coefficient. We discuss several classes of models realizing this framework where an ultralight axion of the necessary size can be generated. In one class of supersymmetric models an ultralight axion is generated by instanton-like effects. In the second class higher-dimensional operators involving couplings of Higgs, standard model singlets, and axion fields naturally lead to an ultralight axion. Further, for the class of models considered the hierarchy between the ultralight scale and the weak scale is maintained. We also discuss the generation of an ultralight scale within string-based models. In the single-modulus Kachru-Kallosh-Linde-Trivedi moduli stabilization scheme an ultralight axion would require an ultralow weak scale. However, within the large volume scenario, the desired hierarchy between the axion scale and the weak scale is achieved. A general analysis of couplings of Higgs fields to instantons within the string framework is discussed and it is shown that the condition necessary for achieving such couplings is the existence of vector-like zero modes of the instanton. Some of the phenomenological aspects of these models are also discussed.

A two-phase description of the quark–nuclear matter hybrid equation of state that takes into account the effect of excluded volume in both the hadronic and the quark-matter phases is introduced. The nuclear phase manifests a reduction of the available volume as density increases, leading to a stiffening of the matter. The quark-matter phase displays a reduction of the effective string tension in the confining density functional from available volume contributions. The nuclear equation of state is based upon the relativistic density-functional model DD2 with excluded volume. The quark-matter equation of state is based upon a quasiparticle model derived from a relativistic density-functional approach and will be discussed in greater detail. The interactions are decomposed into mean scalar and vector components. The scalar interaction is motivated by a string potential between quarks, whereas the vector interaction potential is motivated by higher-order interactions of quarks leading to an increased stiffening at high densities. As an application, we consider matter under compact star constraints of electric neutrality and $\beta$ equilibrium. We obtain mass-radius relations for hybrid stars that form a third family, disconnected from the purely hadronic star branch, and fulfill the $2M_{\odot }$ constraint.

The role of rescaling (expansion or squeezing) of quantized Skyrmions is studied for the spectrum of baryons beginning with nucleon and $\mathrm{\Delta }(1232)$ and with flavors strangeness, charm, or beauty. The expansion of Skyrmions due to the centrifugal forces has influence on the masses of baryons with $u$ and $d$ flavors ($N$ and especially $\mathrm{\Delta }$). In the chirally symmetrical case [Adkins, Nappi, and Witten, Nucl. Phys. B228, 552 (1983)], numerical results are confirmed analytically. The rescaling of Skyrmions has some influence on the spectrum of strange baryons, is more important for the case of charm, and is crucial for baryons with a beauty quantum number, where strong squeezing takes place. Two competing tendencies are clearly observed: expansion of Skyrmions when the isospin (or spin) of the baryon increases and squeezing with the increasing mass of the flavor. For beauty the method seems to be not satisfactory, because the ratio $r_b=F_B/F_{\pi }$ necessary to obtain the observed masses of baryons is different for ${\mathrm{\Lambda }}_b$ and ${\mathrm{\Sigma }}_b$ and should be considerably greater than this ratio (theoretical), given in the literature. The approach itself for the case of beauty can be considered as some kind of a "toy model"; however, the necessity of rescaling of quantized Skyrmions is firmly established. Some pentaquark states with hidden strangeness, charm, or beauty are considered as well.

The $\mu \text{−}\tau$ reflection symmetry $({\nu }_e,{\nu }_{\mu },{\nu }_{\tau })\to ({\overline{\nu }}_e,{\overline{\nu }}_{\tau },{\overline{\nu }}_{\mu })$ and the TM1 mixing (a Pontecorvo–Maki–Nakagawa–Sakata matrix with the first column fixed to the tribimaximal form) are both well compatible with experiments. If both approaches are simultaneously assumed, all lepton mixing parameters except for ${\theta }_{13}$ are predicted. In particular, one expects maximal $CP$ violation ($|\delta |=90°$), maximal atmospheric mixing (${\theta }_{23}=45°$), a slightly less-than-tribimaximal solar mixing angle (${\theta }_{12}\approx 34°$), as well as values of 0 or $\pi$ for the two Majorana phases. We study the renormalization stability of this highly predictive framework when neutrino mass is described by an effective Weinberg operator and by the type I seesaw mechanism, both in the standard model and with supersymmetry.

We consider a dark electroweak phase transition, during which a baryon asymmetry in the dark neutrons and an equal lepton asymmetry in the dark Dirac neutrinos can be simultaneously induced by the $CP$-violating reflection of the dark fermions off the expanding dark Higgs bubbles. The Yukawa couplings for generating the ordinary Majorana neutrino masses can partially convert the dark lepton asymmetry to an ordinary baryon asymmetry in association with the ordinary sphaleron processes. The dark neutron can have a determined mass to serve as a dark matter particle. By further imposing a proper mirror symmetry, the Majorana neutrino mass matrix can have the form of a linear seesaw, while its Dirac $CP$ phase can provide a unique source for the required $CP$ violation.

The strong nature of composite Higgs models manifests at high energies through the growing behavior of the scattering amplitudes of longitudinally polarized weak bosons that leads to the formation of composite resonances as well as nonresonant strong effects. In this work the unitarity of these scattering amplitudes is used as a tool to assess the profile of the composite spectrum of the theory, including nonresonant enhancements, vector resonances and the $CP$-even scalar excitation. These three signatures are then studied in realistic scattering processes at hadron colliders, aiming to estimate the potential to exclude dynamically motivated scenarios of composite Higgs models.

Recent anomalies in $B\to K^{(*)}\ell \ell$ meson decays are consistent with exchange of a heavy $Z^{\prime }$ vector boson. Here we try to connect such new physics to understanding the origin of flavor, by gauging generation number. Phenomenological and theoretical considerations suggest that the smallest viable flavor symmetry [not including any extra U(1) factors] is chiral ${\mathrm{SU}(3)}_L\times {\mathrm{SU}(3)}_R$, which acts only on generation indices and does not distinguish between quarks and leptons. Spontaneous breaking of the symmetry gives rise to the standard model Yukawa matrices, and masses for the 16 $Z^{\prime }$-like gauge bosons, one of which is presumed to be light enough to explain the $B\to K^{(*)}\ell \ell$ anomalies. We perform a bottom-up study of this framework, showing that it is highly constrained by LHC dilepton searches, meson mixing, $Z$ decays and Cabibbo-Kobayashi-Maskawa unitarity. Similar anomalies are predicted for semileptonic decays of $B$ to lighter mesons, with excesses in the $ee$, $\tau \tau$ channels and deficits in $\mu \mu$, but no deviation in $\nu \nu$. The lightest $Z^{\prime }$ mass is $\lesssim 6\mathrm{TeV}$ if the gauge coupling is $\lesssim 1$.

A relativistic formalism for relating the energies of the states of three scalar particles in finite volume to infinite volume scattering amplitudes has recently been developed. This formalism has been used to predict the energy of the state closest to threshold in an expansion in powers of $1/L$, with $L$ the box length. This expansion has been tested previously by a perturbative calculation of the threshold energy in $\lambda {\varphi }^4$ theory, working to third order in $\lambda$ and up to $\mathcal{O}(1/L^6)$ in the volume expansion. However, several aspects of the predicted threshold behavior do not enter until fourth (three-loop) order in perturbation theory. Here I extend the perturbative calculation to fourth order and find agreement with the general prediction. This check also requires a two-loop calculation of the infinite-volume off-shell two-particle scattering amplitude near threshold. As a spin-off, I check the threshold expansion for two particles to the same order, finding agreement with the result that follows from Lüscher’s formalism.

We present a lattice determination of the vector and scalar form factors of the $D\to \pi \ell \nu$ and $D\to K\ell \nu$ semileptonic decays, which are relevant for the extraction of the CKM matrix elements $|V_{cd}|$ and $|V_{cs}|$ from experimental data. Our analysis is based on the gauge configurations produced by the European Twisted Mass Collaboration with $N_f=2+1+1$ flavors of dynamical quarks, at three different values of the lattice spacing ($a\simeq 0.062,0.082,0.089\mathrm{fm}$) and with pion masses as small as 210 MeV. Quark momenta are injected on the lattice using nonperiodic boundary conditions. The matrix elements of both vector and scalar currents are determined for plenty of kinematical conditions in which parent and child mesons are either moving or at rest. Lorentz symmetry breaking due to hypercubic effects is clearly observed in the data and included in the decomposition of the current matrix elements in terms of additional form factors. After the extrapolations to the physical pion mass and to the continuum limit, we determine the vector and scalar form factors in the whole kinematical region from $q^2=0$ up to $q_{\max }^2=(M_D-M_{\pi (K)}{)}^2$ accessible in the experiments, obtaining a good overall agreement with experiments, except in the region at high values of $q^2$ where some deviations are visible. A set of synthetic data points, representing our results for $f_{+}^{D\pi (K)}(q^2)$ and $f_0^{D\pi (K)}(q^2)$ for several selected values of $q^2$, is provided and also the corresponding covariance matrix is available. At zero four-momentum transfer, we get $f_{+}^{D\to \pi }(0)=0.612(35)$ and $f_{+}^{D\to K}(0)=0.765(31)$. Using the experimental averages for $|V_{cd}|f_{+}^{D\to \pi }(0)$ and $|V_{cs}|f_{+}^{D\to K}(0)$, we extract $|V_{cd}|=0.2330(137)$ and $|V_{cs}|=0.945(38)$, respectively. The second row of the CKM matrix is found to be in agreement with unitarity within the current uncertainties: $|V_{cd}{|}^2+|V_{cs}{|}^2+|V_{cb}{|}^2=0.949(78)$.

We developed a Friedrichs-model-like scheme in studying the hadron resonance phenomenology and present that the hadron resonances might be regarded as the Gamow states produced by a Hamiltonian in which the bare discrete state is described by the result of the usual quark potential model and the interaction part is described by the quark pair creation model. In an almost parameter-free calculation, the $X(3862)$, $X(3872)$, and $X(3930)$ state could be simultaneously produced with a quite good accuracy by coupling the three P-wave states, ${\chi }_{c2}(2P)$, ${\chi }_{c1}(2P)$, ${\chi }_{c0}(2P)$ predicted in the Godfrey-Isgur model to the $D\overline{D}$, $D{\overline{D}}^{*}$, $D^{*}{\overline{D}}^{*}$ continuum states. At the same time, we predict that the $h_c(2P)$ state is at about 3890 MeV with a pole width of about 44 MeV. In this calculation, the $X(3872)$ state has a large compositeness. This scheme may shed more light on the long-standing problem about the general discrepancy between the prediction of the quark model and the observed values, and it may also provide reference for future search for the hadron resonance state.

We complete the set of QCD light-cone sum rules for $B\to \pi \pi$ transition form factors, deriving a new sum rule for the timelike-helicity form factor $F_t$ in terms of dipion distribution amplitudes. This sum rule, in the leading twist-two approximation, is directly related to the pion vector form factor. Employing a relation between $F_t$ and other $B\to \pi \pi$ form factors, we obtain also the longitudinal-helicity form factor $F_0$. In this way, all four (axial-)vector $B\to \pi \pi$ form factors are predicted from light-cone sum rules with dipion distribution amplitudes. These results are valid for small dipion masses with large momentum.

In conformal quantum mechanics with the vacuum of a real scaling dimension and with a complete orthonormal set of energy eigenstates, which is preferable under the unitary evolution, the dilatation expectation value between energy eigenstates monotonically decreases along the flow from the UV to the IR. In such conformal quantum mechanics, there exist bounds on scaling dimensions of the physical states and the gauge operators.

We consider three dimensional $N=4$ flat supergravity, with an Abelian R-symmetry enhancing the gravitational phase space. We obtain the field configuration whose asymptotic symmetries at null infinity coincide with the centrally extended $N=4$ super-Bondi-Metzner-Sachs (BMS) algebra. The killing spinors for this generic configuration are obtained together with the energy bounds imposed by supersymmetry. It is explicitly shown that the same algebra can be obtained as a flat (AdS radius $\to \infty$) limit of the combined (2,0) and (0,2) sectors of AdS supergravity.

We study solutions of the Klein-Gordon, Maxwell, and linearized Einstein equations in ${\mathbb{R}}^{1,d+1}$ that transform as $d$-dimensional conformal primaries under the Lorentz group $SO(1,d+1)$. Such solutions, called conformal primary wavefunctions, are labeled by a conformal dimension $\mathrm{\Delta }$ and a point in ${\mathbb{R}}^d$, rather than an on-shell ($d+2$)-dimensional momentum. We show that the continuum of scalar conformal primary wavefunctions on the principal continuous series $\mathrm{\Delta }\in \frac{d}{2}+i\mathbb{R}$ of $SO(1,d+1)$ spans a complete set of normalizable solutions to the wave equation. In the massless case, with or without spin, the transition from momentum space to conformal primary wavefunctions is implemented by a Mellin transform. As a consequence of this construction, scattering amplitudes in this basis transform covariantly under $SO(1,d+1)$ as $d$-dimensional conformal correlators.

We study spontaneous Lorentz symmetry breaking for a four-dimensional massless four-fermion model. Our methodology is based on use of the rationalized propagator. We show that a bumblebee potential arises as a result of one-loop calculations and displays nontrivial minima. Also, we demonstrate that a phase transition restoring Lorentz invariance can occur at a finite temperature.

We investigate gravitational correlation functions in a curved background with the help of nonperturbative renormalization group methods. Beta functions for eleven couplings are derived, two of which correspond to running gauge parameters. A unique ultraviolet fixed point is found, suitable for a UV completion in the sense of Asymptotic Safety. To arrive at a well-behaved flow in a curved background, the regularization must be chosen carefully. We provide two admissible choices to solve this issue in the present approximation. We further demonstrate by an explicit calculation that the Landau limit is a fixed point also for quantum gravity, and additionally show that in this limit, the gauge parameter $\beta$ does not flow.

We consider actions for particles and strings, including twistorial descriptions on 4D Minkowski and ${\mathrm{AdS}}_5$ spacetimes from the point of view of coadjoint orbits for the isometry group. We also consider the collective coordinate dynamics of singular solutions in Chern-Simons (CS) theories and CS theories of gravity. This is a generalization of the work of Einstein, Infeld, and Hoffmann and also has potential points of contact with fluid-gravity correspondence.