Galactic nuclei, the densest stellar environments in the Universe, exhibit a complex geometrical structure. The stars orbiting the central supermassive black hole follow a mass segregated distribution both in the radial distance from the center and in the inclination angle of the orbital planes. The latter distribution may represent the equilibrium state of vector resonant relaxation. In this paper, we build simple models to understand the equilibrium distribution found previously in numerical simulations. Using the method of maximizing the total entropy and the quadrupole mean-field approximation, we determine the equilibrium distribution of axisymmetric two-component gravitating systems with two distinct masses, semimajor axes, and eccentricities. We also examine the limiting case when one of the components dominates over the total energy and angular momentum, approximately acting as a heat bath, which may represent the surrounding astrophysical environment such as the tidal perturbation from the galaxy, a massive perturber, a gas torus, or a nearby stellar system. Remarkably, the bodies above a critical mass in the subdominant component condense into a disk in a ubiquitous way. We identify the system parameters where the transition is smooth and where it is discontinuous. The latter cases exhibit a phase transition between an ordered disklike state and a disordered nearly spherical distribution both in the canonical and in the microcanonical ensembles for these long-range interacting systems.

The precessional motion of binary black holes can be classified into one of three morphologies, based on the evolution of the angle between the components of the spins in the orbital plane: Circulating, librating around 0, and librating around $\pi$. These different morphologies can be related to the binary’s formation channel and are imprinted in the binary’s gravitational wave signal. In this paper, we develop a Bayesian model selection method to determine the preferred spin morphology of a detected binary black hole. The method involves a fast calculation of the morphology which allows us to restrict to a specific morphology in the Bayesian stochastic sampling. We investigate the prospects for distinguishing between the different morphologies using gravitational waves in the Advanced LIGO/Advanced Virgo network with their plus-era sensitivities. For this, we consider fiducial high- and low-mass binaries having different spin magnitudes and signal-to-noise ratios (SNRs). We find that in the cases with high spin and high SNR, the true morphology is strongly favored with ${\log }_{10}$ Bayes factors $\gtrsim 4$ compared to both alternative morphologies when the binary’s parameters are not close to the boundary between morphologies. However, when the binary parameters are close to the boundary between morphologies, only one alternative morphology is strongly disfavored. In the low-spin, high-SNR cases, the true morphology is still favored with a ${\log }_{10}$ Bayes factor $\sim 2$ compared to one alternative morphology, while in the low-SNR cases the ${\log }_{10}$ Bayes factors are at most $\sim 1$ for many binaries. We also consider the gravitational wave signal from GW200129_065458 that has some evidence for precession (modulo data quality issues) and find that there is no preference for a specific morphology. Our method for restricting the prior to a given morphology is publicly available through an easy-to-use python package called bbh_spin_morphology_prior.

We present a study of the tilt-to-length coupling noise during the LISA Pathfinder mission and how it depended on the system’s alignment. Tilt-to-length coupling noise is the unwanted coupling of angular and lateral spacecraft or test mass motion into the primary interferometric displacement readout. It was one of the major noise sources in the LISA Pathfinder mission and is likewise expected to be a primary noise source in LISA. We demonstrate here that a recently derived and published analytical model describes the dependency of the LISA Pathfinder tilt-to-length coupling noise on the alignment of the two freely falling test masses. This was verified with the data taken before and after the realignments performed in March (engineering days) and June 2016, and during a two-day experiment in February 2017 (long cross-talk experiment). The latter was performed with the explicit goal of testing the tilt-to-length coupling noise dependency on the test mass alignment. Using the analytical model, we show that all realignments performed during the mission were only partially successful and explain the reasons why. In addition to the analytical model, we computed another physical tilt-to-length coupling model via a minimizing routine making use of the long cross-talk experiment data. A similar approach could prove useful for the LISA mission.

The Genetically Evolved NEutrino Telescopes for Improved Sensitivity project seeks to optimize detectors in physics for science outcomes in high-dimensional parameter spaces. In this project, we designed an antenna using a genetic algorithm with a science outcome directly as the sole figure of merit. This paper presents initial results on the improvement of an antenna design for in-ice neutrino detectors using the current Askaryan Radio Array (ARA) experiment as a baseline. By optimizing for the effective volume using the evolved antenna design in ARA, we improve upon ARA’s simulated sensitivity to ultrahigh energy neutrinos by 11%, despite using limited parameters in this initial investigation. Future improvements will continue to increase the computational efficiency of the genetic algorithm and the complexity and fitness of the antenna designs. This work lays the foundation for continued research and development of methods to increase the sensitivity of detectors in physics and other fields in parameter spaces of high dimensionality.

We provide a formulation of potential nonrelativistic quantum chromodynamics (pNRQCD) suitable for calculating binding energies and matrix elements of generic hadron and multihadron states made of heavy quarks in $SU(N_c)$ gauge theory using quantum Monte Carlo techniques. We compute masses of quarkonium and triply heavy baryons in order to study the perturbative convergence of pNRQCD and validate our numerical methods. Further, we study $SU(N_c)$ models of composite dark matter and provide simple power series fits to our pNRQCD results that can be used to relate dark meson and baryon masses to the fundamental parameters of these models. For many systems comprised entirely of heavy quarks, the quantum Monte Carlo methods employed here are less computationally demanding than lattice field theory methods, although they introduce additional perturbative approximations. The formalism presented here may therefore be particularly useful for predicting composite dark matter properties for a wide range of $N_c$ and heavy fermion masses.

We consider the possibility to detect cosmic light dark matter (DM), i.e., axions and dark photons, of mass $\sim {10}^{-6}\mathrm{eV}$ and $\sim {10}^{-4}\mathrm{eV}$, by magnetic excitation in a magnet with strong hyperfine interaction. In particular, we consider a canted antiferromagnet, ${\text{MnCO}}_3$, as a concrete candidate material. With spin transfer between nuclear and electron spins allowed by the hyperfine interaction, nuclear spins become naturally highly polarized due to an effective (electron-spin-induced) magnetic field, and have long-range interactions with each other. The collective precession of nuclear spins, i.e., a nuclear magnon, can be generated by the DM field through the nucleon-DM interaction, while they are also sensitive to the electron-DM interaction through the electron-nuclear spin mixing. Compared with conventional nuclear-spin precession experiments, this system as a DM sensor is sensitive to higher frequency needing only a small static magnetic field applied. The system also has collective precession of electron spins, mixed with nuclear spins, as the additional channels that can be used for DM probes. We estimate the sensitivity under appropriate readout setups such as an inductive pick-up loop associated with an LC resonant circuit, or a photon cavity with a photon counting device. We show that this method covers an unexplored parameter region of light bosonic DM.

We investigate the single production of vectorlike quarks at the High Luminosity LHC (HL-LHC). With the assumed (enhanced) couplings to third generation quarks of the standard model, vectorlike quarks $B/X$ are produced in association with a bottom ($b$) or top ($t$) quark, which correspond to $Bbq$ and $Btq/Xtq$ production modes, including an additional soft forward jet from the spectator quark ($q$). This study focuses on high-mass vectorlike quarks $B/X$ decaying into a top quark and a $W$ boson, resulting in the final state jets emerging from hadronically decaying top quark ($t\to Wb$) and $W$ boson ($W\to q{\overline{q}}^{\prime }$). The events with $W$ boson and $t$ quark have been analyzed using tagging techniques for large-radius jets. The scan ranges of the mass ($1000<m_{B/X}<3000\mathrm{GeV}$) for the relative width ${\mathrm{\Gamma }}_{B/X}/m_{B/X}=0.1$ and ${\mathrm{\Gamma }}_{B/X}/m_{B/X}=0.01$ of vectorlike $B/X$ quarks have been investigated. From the results of the analysis, the masses of vectorlike quarks $B(X)$ up to 2491 (2364) GeV and 2018 (1873) GeV can be excluded corresponding to these relative width cases at 95% CL depending on the type and branching scenarios at integrated luminosity projection of $3{\mathrm{ab}}^{-1}$ at the HL-LHC.

We study a prediction on neutrino observables in a nonsupersymmetric renormalizable $SO(10)$ grand unified theory model that contains a $\mathbf{10}$ complex scalar field and a $\mathbf{126}$ scalar field whose Yukawa couplings with $\mathbf{16}$ matter fields provide the quark and charged lepton Yukawa couplings, neutrino Dirac Yukawa coupling and Majorana mass for the singlet neutrinos. The $SO(10)$ breaking is achieved in two steps by a $\mathcal{O}({10}^{15})\mathrm{GeV}$ vacuum expectation value (VEV) of a $\mathbf{54}$ real scalar field and a $\mathcal{O}({10}^{14})\mathrm{GeV}$ VEV of the $\mathbf{126}$ field. First, we analyze the gauge coupling unification conditions and determine the VEV of the $\mathbf{126}$ field. Next, we constrain the Yukawa couplings of the $\mathbf{10}$ and $\mathbf{126}$ fields at the scale of the $\mathbf{126}$ field’s VEV from experimental data on quark and charged lepton masses and quark flavor mixings. Then we express the active neutrino mass with the above Yukawa couplings and the $\mathbf{126}$ field’s VEV based on the Type-1 seesaw mechanism, and fit neutrino oscillation data, thereby deriving a prediction on poorly or not measured neutrino observables. What distinguishes our work from previous studies is that we do not assign Peccei-Quinn charges on visible sector fields so that the $\mathbf{10}$ scalar field and its complex conjugate both have Yukawa couplings with $\mathbf{16}$ matter fields. From the fitting of neutrino oscillation data, we find that not only the normal neutrino mass hierarchy, but also the inverted hierarchy can be realized. We also reveal that in the normal hierarchy case, the Dirac $CP$ phase of the neutrino mixing matrix ${\delta }_{CP}$ is likely in the ranges of $-2.4<{\delta }_{CP}<-1.2$ and $1.2<{\delta }_{CP}<2.4$, and not in the region with ${\delta }_{CP}\sim \pi$, and that in the normal hierarchy case, ${\theta }_{23}$ is likely in the upper octant and in the range of $0.50\lesssim {\sin }^2{\theta }_{23}\lesssim 0.55$.

We analyze the two-loop level $R$-parity violating supersymmetric contribution to the electric and chromoelectric dipole moments of fermions with a lepton and a gaugino in the intermediate state. It is found that this contribution can be sufficiently enhanced with large $\tan \beta$ and that it can have comparable size with the currently known $R$-parity violating Barr-Zee type process within TeV scale supersymmetry breaking. We also give new upper limits on $R$-parity violating couplings given by the atomic electric dipole moment and molecular beam experiments.

The spectra of two-dimensional $su(2)$ gauge theories coupled to a single massless Majorana fermion in integer representations, $J$, are numerically investigated using the discrete light-cone Hamiltonian. One of our aims is to explore the possible presence of massless states for $J>2$ in spite of the absence of a continuous symmetry. After comparing to existing results for $J=1$ (adjoint fermions), we present results for $J=2$, 3, 4. As expected, for $J=2$ there are no massless states but in contrast to the $J=1$ theory, the lightest state is a boson. We find exact massless modes in the bosonic and fermionic sector for all values of total momentum for $J=3$ and $J=4$ and, in each sector, the number of massless modes grows with the value of the total momentum. In addition to the spectrum, we present results on the particle number and momentum fraction distributions and argue for a separation of bulk states from edge states.

Considerable attention has been paid to the study of the quantum geometry of nonrotating black holes within the framework of loop quantum cosmology. This interest has been reinvigorated since the introduction of a novel effective model by Ashtekar, Olmedo, and Singh. Despite recent advances in its foundation, there are certain questions about its quantization that still remain open. Here we complete this quantization taking as starting point an extended phase space formalism suggested by several authors, including the proposers of the model. Adopting a prescription that has proven successful in loop quantum cosmology, we construct an operator representation of the Hamiltonian constraint. By searching for solutions to this constraint operator in a sufficiently large set of dual states, we show that it can be solved for a continuous range of the black hole mass. This fact seems in favor of a conventional classical limit (at least for large masses) and contrasts with recent works that advocate a discrete spectrum. We present an algorithm that determines the solutions in closed form. To build the corresponding physical Hilbert space and conclude the quantization, we carry out an asymptotic analysis of those solutions, which allows us to introduce a suitable inner product on them.

We calculate the anomalous part of the polarization tensor of Dirac fermions in $2+1$ dimensions in the presence of impurities described by the scattering rate $\mathrm{\Gamma }$ for arbitrary external frequency and momenta. We consider two different versions of the Pauli-Villars subtractions and discuss their physical consequences.

The quantum extension of the Kruskal spacetime indicates the potential existence of a companion black hole in the universe earlier than ours. It is shown that the radiation from the companion black hole can enter its horizon, pass through the deep Planck region, and show up from the white hole in our Universe. These radiation inlay extra bright rings in the image of the black hole in our Universe, and some of these rings appear distinctly in the shadow region. Therefore, the image of the black hole observed by us encodes the information of quantum gravity. The positions and widths of the bright rings are predicted precisely. The predictive values for massive black holes are universal for a quite general class of quantum modified spacetime with the scenario of black hole to white hole transition. Thus, our result opens a new experimental window to test this prediction of quantum gravity.

We investigate the influence of a time-varying spacetime background on the vacuum polarization of a massless quantum field confined to a Casimir cavity. The background is modeled as an anisotropic Bianchi-I spacetime, in which small time-dependent perturbations around the flat spacetime are vanishing in the far past and future. The spacetime admits asymptotic Minkowskian regions, thus allowing for an unambiguous definition of the in- and out-field vacua. Following Schwinger’s proper-time approach, we evaluate the vacuum polarization inside the Casimir cavity. We show the presence of a small shift in the field vacuum energy, once the perturbation is over. The time-dependent background has distorted the field modes, causing a permanent change in the zero-point energy of the field confined to the Casimir apparatus. As an example, we briefly consider the case of a weak gravitational wave background, which can be locally identified with the previously employed Bianchi-I spacetime model. The present effect appears as a sort of gravitational memory of the Casimir effect.

A Euclidean bounce describing vacuum decay can be considered as an infinite stack of concentric thin shells to which a thin-wall action can be assigned. The integral over all shells produces then a tunneling action that is precisely the action functional in field space of the so-called tunneling potential formalism. This procedure, which works also when gravity is included, gives the simplest derivation of such actions.

This work explores the dynamical stability of cosmological models where dark matter and dark energy can nonminimally couple to spacetime (scalar) curvature. Two different scenarios are presented here. In the initial case, only dark matter sector is coupled to curvature in the presence of a quintessence scalar field. In the second case both dark matter and the quintessence field are coupled to curvature. It is shown that one can get an accelerating expansion phase of the Universe in both the cases. The nature of the fixed points shows that there can be stable or unstable phases where the curvature coupling vanishes and dark energy and dark matter evolve independently. On the other hand there can be stable accelerating expansion phases where both the components are coupled to curvature.

We use the scattering method to calculate the gravitational wave from axions annihilation in the axion cloud formed by the superradiance process around the Kerr black hole. We consider axions annihilating to gravitons as a three-body decay process and then calculate the corresponding decay width. In this approach, we can simply obtain the radiation power of gravitational wave and give the analytical approximate result with the spin effects of the Kerr black hole. Our study can also provide a cross-check to the numerical results in the traditional method.

We perform a long and accurate large-eddy simulation of a binary neutron star merger, following the newly formed remnant up to 110 milliseconds. The combination of high-order schemes, high-resolution, and the gradient subgrid-scale model allows us to have among the highest effective resolutions ever achieved. Our results show that, although the magnetic fields are strongly amplified by the Kelvin-Helmholtz instability, they are coherent only over very short spatial scales until $t\gtrsim 30\mathrm{ms}$. Around that time, magnetic winding becomes more efficient leading to a linear growth of the toroidal component and slowly ordering the field to more axisymmetric large scales. The poloidal component only starts to grow at small scales at much later times $t\gtrsim 90\mathrm{ms}$, in a way compatible with the magneto-rotational instability. No strong large-scale poloidal field or jet is produced in the timescales spanned by our simulation, although there is a helicoidal structure gradually developing at late times. We highlight that soon after the merger the magnetic field topology is always strongly dominated by toroidal structures, with a complex distribution in the meridional plane and highly turbulent perturbations. The topology present before the merger is completely erased and forgotten, as long as the initial magnitude of the magnetic field has realistic values. In fact, we advise against the widespread use of unrealistic very strong large-scale initial magnetic fields, since they might affect significantly the postmerger topological outcome, which would be therefore strongly biased by such an artificial choice. Finally, we confirm the universality of the evolved topology, even when starting with very different magnetic fields confined to the outermost layers of each neutron star.

We propose a novel realization of the Nelson-Barr mechanism “seeded” by a dark sector containing scalars and vectorlike quarks. Charge parity ($CP$) and a ${\mathcal{Z}}_8$ symmetry are spontaneously broken by the complex vacuum expectation value of a singlet scalar, leaving a residual ${\mathcal{Z}}_2$ symmetry that stabilizes dark matter (DM). A complex Cabibbo-Kobayashi-Maskawa matrix arises via one-loop corrections to the quark mass matrix mediated by the dark sector. In contrast with other proposals where nonzero contributions to the strong $CP$ phase arise at the one-loop level, in our case this occurs only at two loops, enhancing naturalness. Our scenario also provides a viable weakly interacting massive particle scalar DM candidate.

We consider the phenomenology of the Higgs bosons in the hidden sector model mediated by an additional SU(2) scalar doublet. With the mediator scalar doublet, the Higgs sector of the model is extended to be that of the two Higgs doublet model of type I. The mediator scalar doublet is connected to the hidden sector with the hidden ${\mathrm{U}(1)}_X$ gauge charge. Then the ${\mathrm{U}(1)}_X$ gauge symmetry is spontaneously broken by the electroweak symmetry breaking and the hidden U(1) gauge boson gets the mass to give rise to a dark $Z$ boson. Using the programs higgsbounds and higgssignals, we incorporate current experimental limits from LEP, Tevatron, and LHC to examine the Higgs sector in our model and derive constraints on model parameters together with the electroweak processes. As a result, our model favors the light dark $Z$ boson. We also investigate the implications of the model on the dark matter phenomenology when the hidden fermion is a dark matter candidate.