The gauged $U(1{)}_{L_{\mu }-L_{\tau }}$ extension of the Standard Model is a very simple framework that can alleviate the tension in muon anomalous magnetic dipole moment, reinforced by the recent Fermilab measurement. We explore experimental probes of the $(g-2{)}_{\mu }$ target with a general treatment of kinetic mixing between the $Z^{\prime }$ gauge boson and the photon. The physical value of the kinetic mixing depends on a free parameter of the model and energy scale of a process. We find neutrino constraints on the $(g-2{)}_{\mu }$ target including Borexino, coherent elastic neutrino-nucleus scattering, and white dwarfs are sensitive to this freedom and can be lifted if the kinetic mixing lies in proximity of zero at low momentum transfer. As a further step, we explore $L_{\mu }-L_{\tau }$ charged dark matter with a thermal origin and show that the same scenario of kinetic mixing can relax existing direct detection constraints and predict novel recoil energy dependence in the upcoming searches. Future joint effort of neutrino and dark matter experiments and precision spectral measurement will be the key to test such a theory.

Many extensions of the Standard Model of particle physics contain new electrically-neutral fermions. Should one of these particles be discovered, questions will naturally arise regarding its nature. For instance: is it a self-conjugate particle (i.e., is it a Dirac or a Majorana fermion)?, does it interact via the Standard Model force carriers or something else? One set of well-motivated particles in this class are heavy neutral leptons (HNLs), Standard Model gauge-singlet fermions that mix with the neutrinos and may be produced in meson decays. We demonstrate that measuring the three body decays of the HNL (or phenomenologically similar heavy fermions) can help determine whether they are Majorana or Dirac fermions. We also investigate the ability to distinguish among different models for the physics responsible for the HNL decay. We compare the reach assuming full and partial event reconstruction, and propose experimental analyses. Should a new fermion be discovered, studying its three body decays provides a powerful diagnostic tool of its nature.

In this paper we introduce the axial gauge field to the framework of the quantum kinetic theory with vector gauge field in the massless limit. Treating the axial gauge field on an equal footing with the vector gauge field, we construct a consistent solution to the kinetic equations up to the first order in gradient expansion, or equivalently the semiclassical expansion. The intuitive extension of quantum kinetic theory presented in this work provides a natural generalization, and turns out to give rise to the covariant anomaly and the covariant currents. The corresponding consistent currents can be obtained from the covariant ones by adding the Chern-Simons current. We use the consistent currents to calculate various correlation functions among currents and energy-momentum tensor in equilibrium state.

We consider a class of holographic tensor networks that are efficiently contractible variational ansatz, manifestly (approximate) quantum error correction codes, and can support power-law correlation functions. In the case when the network consists of a single type of tensor that also acts as an erasure correction code, we show that it cannot be both locally contractible and sustain power-law correlation functions. Motivated by this no-go theorem, and the desirability of local contractibility for an efficient variational ansatz, we provide guidelines for constructing networks consisting of multiple types of tensors that can support power-law correlation. We also provide an explicit construction of one such network, which approximates the holographic happy pentagon code in the limit where variational parameters are taken to be small.

The light trajectory in the gravitational field of one body at rest with monopole and quadrupole structure is determined in the second post-Newtonian (2PN) approximation. The terms in the geodesic equation for light rays are separated into time-independent tensorial coefficients and four kinds of time-dependent scalar functions. Accordingly, the first and second integration of the geodesic equation can be reduced in each case to only four kinds of scalar master integrals. These integrals can be solved in closed form by recurrence relations. The 2PN terms of monopole and quadrupole contribute less than 1 nanoarcsecond to the total light deflection. There are, however, enhanced terms in the 2PN light deflection, both in the case of monopole and quadrupole. These enhanced 2PN terms are caused by the use of an impact vector which is indispensable for modeling of real astrometric measurements. In the case of grazing light rays at Jupiter and Saturn, the enhanced 2PN terms, caused by the quadrupole structure of the massive body, amount up to 0.95 microarcseconds and 0.29 microarcseconds, respectively. Thus, the 2PN quadrupole terms are relevant for high-precision astrometry on the submicroarcsecond scale of accuracy.

We study the density structures of dark matter subhalos for both cold dark matter and self-interacting dark matter models using high-resolution cosmological $N$-body simulations. We quantify subhalo’s central density at 150 pc from the center of each subhalo at the classical dwarf spheroidal and ultrafaint dwarf scales found in Milky-Way sized halos. By comparing them with observations, we find that the self-interacting scattering cross section of $\sigma /m<3{\mathrm{cm}}^2{\mathrm{g}}^{-1}$ is favored. Due to the combination of hosts’ tide and self-interactions, the central density of subhalos with small pericenter shows a noticeable difference between the cold and the self-interacting models, indicating that Milky-Way satellites with small pericenter are ideal sites to further constrain the nature of dark matter by future large spectroscopic surveys.

Pulsars have long been studied in the electromagnetic spectrum. Their environments are rich in high-energy cosmic-ray electrons and positrons likely enriching the interstellar medium (ISM) with such particles. In this work we use recent cosmic-ray observations from the AMS-02, CALET, and DAMPE Collaborations to study the averaged properties of the local Milky Way pulsar population. We perform simulations of the local Milky Way pulsar population, for interstellar medium assumptions in agreement with a range of cosmic-ray nuclei measurements. Each such simulation contains $\sim {10}^4$ pulsars of unique age, location, initial spin-down power, and cosmic-ray electron/positron spectra. We produce more than $7\times {10}^3$ such Milky Way pulsar simulations. We account for and study (i) the pulsars’ birth rates and the stochastic nature of their birth, (ii) their initial spin-down power distribution, (iii) their time evolution in terms of their braking index and characteristic spin-down timescale, (iv) the fraction of spin-down power going to cosmic-ray electrons and positrons, and (v) their propagation through the interstellar medium and the heliosphere. We find that pulsars of ages $\sim {10}^5–{10}^7\mathrm{yr}$, have a braking index that on average has to be 3 or larger. Given that electromagnetic spectrum observations of young pulsars find braking indices lower than 3, our work provides strong hints that pulsars’ braking index increases on average as they age, allowing them to retain some of their rotational energy. Moreover, we find that pulsars have relatively uniform properties as sources of cosmic-ray electrons and positrons in terms of the spectra they produce and likely release $O(10\%)$ of their rotational energy to cosmic rays in the ISM. Finally, we find at $\simeq 12\mathrm{GeV}$ positrons a spectral feature that suggests a new subpopulation of positron sources contributing at these energies.

We study the weak mixing of photons and relativistic axionlike particles (axions) in plasmas with background magnetic fields, $\mathbf{B}$. We show that, to leading order in the axion-photon coupling, the conversion probability, $P_{\gamma \to a}$, is given by the one-dimensional power spectrum of the magnetic field components perpendicular to the particle trajectory. Equivalently, we express $P_{\gamma \to a}$ as the Fourier transform of the magnetic field autocorrelation function, and establish a dictionary between properties of the real-space magnetic field and the energy-dependent conversion probability. For axions more massive than the plasma frequency, ($m_a>{\omega }_{\mathrm{pl}}$), we use this formalism to analytically solve the problem of perturbative axion-photon mixing in a general magnetic field. In the general case where ${\omega }_{\mathrm{pl}}/m_a$ varies arbitrarily along the trajectory, we show that a naive application of the standard formalism for “resonant” conversion can give highly inaccurate results, and that a careful calculation generically gives nonresonant contributions at least as large as the resonant contribution. Furthermore, we demonstrate how techniques based on the Fast Fourier Transform provide a new, highly efficient numerical method for calculating axion-photon mixing. We briefly discuss magnetic field modeling in galaxy clusters in the light of our results and argue, in particular, that a recently proposed “regular” model used for studying axion-photon mixing (specifically applied to the Perseus cluster) is inconsistent with observations. Our formalism suggests new methods to search for imprints of axions, and will be important for spectrographs with percent level sensitivity, which includes existing X-ray observations by Chandra as well as the upcoming Athena mission.

Low-energy data, combined with renormalization group equations, can predict new physics at far higher energy scales. In this paper, we consider the possibility that the measured Higgs boson mass and top quark mass hint at a five-dimensional gauge-Higgs unification (5D GHU) model at a scale above TeV. We note that the vanishing of the Higgs quartic coupling and the proximity of the top quark Yukawa coupling and weak gauge coupling at high scales, inferred from the experimental data, are in harmony with 5D GHU, because in 5D GHU models the Higgs quartic coupling is forbidden by the 5D gauge symmetry and the Yukawa couplings and the weak gauge coupling originate from a common 5D gauge coupling. Based on the above insight, we propose a 5D GHU model where the Standard Model fermions are embedded in 5D fermions in a way to tightly relate the top Yukawa coupling with the weak gauge coupling. Also, the model predicts the presence of vectorlike fermions (other than the Kaluza-Klein modes), which can affect the renormalization group evolutions of the 4D theory and reconcile the scale of vanishing Higgs quartic coupling and that of equality of the top Yukawa and weak gauge couplings, thereby achieving a successful matching of the 4D theory with 5D GHU. We predict the vectorlike fermion mass and the compactification scale of 5D GHU from the conditions for the successful matching.

We calculate the masses of the vector and axial vector mesons as well as the nucleon and the delta resonance in the chiral symmetry restored vacuum. This is accomplished by separating the quark operators appearing in the QCD sum rules for these hadrons into the chiral symmetric and symmetry breaking parts depending on the contributions of the fermion zero modes. We then extract the vacuum expectation values of all the separated parts of the quark operators using the QCD sum rule relations for these hadrons with their vacuum masses and widths. By taking the chiral symmetry breaking parts to be zero while keeping the symmetric operators to their vacuum values, we obtain the chiral symmetric part of the hadron masses. We find that the masses of chiral partners, such as the $(\rho ,a_1)$ and $(K^{*},K_1)$, become degenerate to values between 500 and 600 MeV in the chiral symmetry restored vacuum, while parity partners $(\omega ,f_1)$ that are chiral partners only in the limit where the disconnected diagrams are neglected remain nondegenerate with masses (655, 1060) MeV, respectively. The masses of the nucleon and the delta are also found to reduce to about 500 and 600 MeV, respectively, in the chiral symmetric vacuum. This shows that while chiral symmetry breaking is responsible for the mass difference between chiral partner, both the meson and baryon retain a nontrivial fraction of their masses in the chiral symmetry restored vacuum.

We discuss general aspects of renormalization group (RG) flows between two conformal fixed points in 4D with a broken continuous global symmetry in the UV. Every such RG flow can be described in terms of the dynamics of Nambu-Goldstone bosons of broken conformal and global symmetries. We derive the low-energy effective action that describes this class of RG flows from basic symmetry principles. We view the theory of Nambu-Goldstone bosons as a theory in anti–de Sitter space with the flat space limit. This enables an equivalent 3D CFT (${\mathrm{CFT}}_3$) formulation of these 4D RG flows in terms of spectral deformations of a generalized free ${\mathrm{CFT}}_3$. We utilize this dual description to impose further constraints on the low-energy effective action associated with unitary RG flows in 4D by invoking the chaos bound in 3D. This approach naturally provides a set of independent monotonically decreasing $C$-functions for 4D RG flows with global symmetry breaking by explicitly relating 4D $C$-functions with certain out-of-time-order correlators that diagnose chaos in 3D. We also comment on a more general connection between RG and chaos in QFT.

The axionlike particles with ultralight mass ($\sim {10}^{-22}\mathrm{eV}$) can be a possible candidate of dark matter, known as the fuzzy dark matter (FDM). These particles form a Bose-Einstein condensate in the early Universe which can explain the dark matter density distribution in galaxies at the present time. We study the time evolution of ultralight axionlike field in the near region of a strong gravitational wave (GW) source, such as binary black hole merger. We show that GWs can lead to the generation of field excitations in a spherical shell about the source that eventually propagate out of the shell to minimize the energy density of the field configuration. These excitations are generated toward the end of the merger and in some cases even in the ringdown phase of the merger, therefore it can provide a qualitatively distinct prediction for changes in the GW waveform due to the presence of FDM. This would be helpful in investigating the existence of FDM in galaxies.

In higher dimensions, we explore planar hairy black hole configurations for a special subclass of the Horndeski theory defined by two coupling functions depending on the kinetic term and enjoying shift symmetry and reflection symmetry. For this analysis, we derive a set of new solutions given by time-dependent as well as time-independent scalar field configurations. Additionally, we calculate their thermodynamic quantities by using Wald formalism satisfying the first law of thermodynamics as well as a Smarr relation. Together with the above, the Wald procedure allows us to compute the shear viscosity, showing that for a suitable choice of the coupling functions the Kovtun-Son-Starinets bound is violated.

We investigate the timelike geodesics and the periapsis precession of orbits in the Fisher-Janis-Newman-Winicour-Wyman spacetime. This spacetime represents the naked singularity spacetime in the Einstein-massless scalar system. We revisit the results in the previous studies and relax the assumptions about the eccentricity of a bound orbit and the size of a semilatus. We find that the negative periapsis precession occurs when the spacetime sufficiently deviates from the Schwarzschild spacetime. In particular, for the small eccentric orbits, we show the negative periapsis precession occurs for $\gamma <1/2$, where $\gamma$ is the deviation parameter from the Schwarzschild spacetime. We also obtain the analytical solutions for the special cases of $\gamma =0,1/2,1/4$. Then we show that the negative precession never occurs for $\gamma =1/2$.

The discovery of gravitational waves (GWs) from the compact binary components by LIGO/Virgo Collaboration provides an unprecedented opportunity for testing gravity in the strong and highly dynamical field regime of gravity. Currently a lot of model-independent tests have been performed by LIGO/Virgo Collaboration and no any significant derivation from general relativity has been found. In this paper, we study the parity violating effects on the propagation of GWs in the Nieh-Yan modified teleparallel gravity, a theory which modifies general relativity by a parity violating Nieh-Yan term. We calculate the corresponding parity violating waveform of GWs produced by the coalescence of compact binaries. By comparing the two circular polarization modes, we find the effects of the velocity birefringence of GWs in their propagation caused by the parity violation due to the Nieh-Yan term, which are explicitly presented in the GW waveforms by the phase modification. With such phase modifications to the waveform, we perform the full Bayesian inference with the help of the open source software Bilby on the GW events of binary black hole merges (BBH) in the LIGO-Virgo catalogs GWTC-1 and GWTC-2. We do not find any significant evidence of parity violation due to the parity violating Nieh-Yan term and thus place an upper bound on the energy scale $M_{\mathrm{PV}}<6.5\times {10}^{-42}\mathrm{GeV}$ at 90% confidence level, which represents the first constraint on the Nieh-Yan modified teleparallel gravity so far.

Detection of a stochastic background of gravitational waves is likely to occur in the next few years. Beyond searches for the isotropic component of a stochastic gravitational-wave background, there have been various mapping methods proposed to target anisotropic backgrounds. Some of these methods have been applied to data taken by the Laser Interferometer Gravitational-wave Observatory (LIGO) and Virgo. Specifically, these directional searches have focused on mapping the intensity of the signal on the sky via maximum-likelihood solutions. We compare this intensity mapping approach to a previously proposed, but never employed, amplitude-phase mapping method to understand whether this latter approach may be employed in future searches. We build up our understanding of the differences between these two approaches by analyzing simple toy models of time-stream data, and we run mock-data mapping tests for the two methods. We find that the amplitude-phase method is only applicable to the case of a background which is phase coherent on large scales or, at the very least, has an intrinsic coherence scale that is larger than the resolution of the detector. Otherwise, the amplitude-phase mapping method leads to an overall loss of information, with respect to both phase and amplitude. Since we do not expect these phase-coherent properties to hold for any of the gravitational-wave background signals we hope to detect in the near future, we conclude that intensity mapping is the preferred method for such backgrounds.

We present Planck-low-py, a binned low-$\ell$ temperature and $E$-mode polarization likelihood, as an option to facilitate ease of use of the Planck 2018 large scale data in joint-probe analysis and forecasting. It is written in python and compresses the $\ell <30$ temperature and polarization angular power spectra information from Planck into two log-normal bins in temperature and seven in polarization. These angular scales constrain the optical depth to reionization and provide a lever arm to constrain the tilt of the primordial power spectrum. Using Planck-low-py, we show that cosmological constraints on $\mathrm{\Lambda }\mathrm{CDM}$ model parameters, and on parameters including running and isocurvature, agree with those derived with the full Commander and SimAll likelihoods from the Planck legacy release.

Upcoming measurements of the small-scale primary cosmic microwave background (CMB) temperature and polarization power spectra ($TT/TE/EE$) are anticipated to yield transformative constraints on new physics, including the effective number of relativistic species in the early universe ($N_{\mathrm{eff}}$). However, at multipoles $\ell \gtrsim 3000$, the CMB power spectra receive significant contributions from gravitational lensing. While these modes still carry primordial information, their theoretical modeling requires knowledge of the CMB lensing convergence power spectrum, $C_L^{\kappa \kappa }$, including on small scales where it is affected by nonlinear gravitational evolution and baryonic feedback processes. Thus, the high-$\ell$ (lensed) CMB is sensitive to these late-time, nonlinear effects. Here, we show that inaccuracies in the modeling of $C_L^{\kappa \kappa }$ can yield surprisingly large biases on cosmological parameters inferred from the lensed CMB power spectra measured by the upcoming Simons Observatory and CMB-S4 experiments. For CMB-S4, the biases can be as large as $1.6\sigma$ on the Hubble constant $H_0$ in a fit to $\mathrm{\Lambda }\mathrm{CDM}$ and $1.2\sigma$ on $N_{\mathrm{eff}}$ in a fit to $\mathrm{\Lambda }\mathrm{CDM}+N_{\mathrm{eff}}$. We show that these biases can be mitigated by explicitly discarding all $TT$ data at $\ell >3000$ or by marginalizing over parameters describing baryonic feedback processes, both at the cost of slightly larger error bars. We also discuss an alternative, data-driven mitigation strategy based on delensing the CMB $T$ and $E$-mode maps. Finally, we show that analyses of upcoming data will require Einstein-Boltzmann codes to be run with much higher numerical precision settings than is currently standard, so as to avoid similar— or larger—parameter biases due to inaccurate theoretical predictions.

This work and its companion paper, Amon et al. [Phys. Rev. D 105, 023514 (2022)], present cosmic shear measurements and cosmological constraints from over 100 million source galaxies in the Dark Energy Survey (DES) Year 3 data. We constrain the lensing amplitude parameter $S_8\equiv {\sigma }_8\sqrt{{\mathrm{\Omega }}_{\mathrm{m}}/0.3}$ at the 3% level in $\mathrm{\Lambda }\mathrm{CDM}$: $S_8=0.759_{-0.023}^{+0.025}$ (68% CL). Our constraint is at the 2% level when using angular scale cuts that are optimized for the $\mathrm{\Lambda }\mathrm{CDM}$ analysis: $S_8=0.772_{-0.017}^{+0.018}$ (68% CL). With cosmic shear alone, we find no statistically significant constraint on the dark energy equation-of-state parameter at our present statistical power. We carry out our analysis blind, and compare our measurement with constraints from two other contemporary weak lensing experiments: the Kilo-Degree Survey (KiDS) and Hyper-Suprime Camera Subaru Strategic Program (HSC). We additionally quantify the agreement between our data and external constraints from the Cosmic Microwave Background (CMB). Our DES Y3 result under the assumption of $\mathrm{\Lambda }\mathrm{CDM}$ is found to be in statistical agreement with Planck 2018, although favors a lower $S_8$ than the CMB-inferred value by $2.3\sigma$ (a $p$-value of 0.02). This paper explores the robustness of these cosmic shear results to modeling of intrinsic alignments, the matter power spectrum and baryonic physics. We additionally explore the statistical preference of our data for intrinsic alignment models of different complexity. The fiducial cosmic shear model is tested using synthetic data, and we report no biases greater than $0.3\sigma$ in the plane of $S_8\times {\mathrm{\Omega }}_{\mathrm{m}}$ caused by uncertainties in the theoretical models.