We revisit Wyman’s “other” scalar field solution of the Einstein equations and its Sultana generalization to positive cosmological constant, which has a finite 3-space and corresponds to a special case of a stiff fluid solution proposed by Buchdahl and Land and, later, by Ibañez and Sanz to model relativistic stars. However, there is a hidden cosmological constant and the peculiar geometry prevents the use of this spacetime to model relativistic stars.

Primordial magnetic fields can change the recombination history of the Universe by inducing clumping in the baryon density at small scales. They were recently proposed as a candidate model to relieve the Hubble tension. We investigate the consistency of the constraints on a clumping factor parameter $b$ in a simplistic model, using the latest CMB data from Planck, ACT DR4 and SPT-3G 2018. For the combined CMB data alone, we find no evidence for clumping being different from zero, though when adding a prior on $H_0$ based on the latest distance-ladder analysis of the SH0ES team, we report a weak detection of $b$. Our analysis of simulated datasets shows that ACT DR4 has more constraining power with respect to SPT-3G 2018 due to the degeneracy breaking power of the temperature (TT) band powers (not included in SPT). Simulations also suggest that the temperature cross polarisation (TE) and the polarisation (EE) power spectra of the two datasets should have the same constraining power. However, the ACT DR4 TE,EE constraint is tighter than expectations, while the SPT-3G 2018 one is looser. While this is compatible with statistical fluctuations, we explore systematic effects which may account for such deviations. Overall, the ACT results are only marginally consistent with Planck or SPT-3G, at the $2–3\sigma$ level within $\mathrm{\Lambda }\mathrm{CDM}+b$ and $\mathrm{\Lambda }\mathrm{CDM}$, while Planck and SPT-3G are in good agreement. Combining the CMB data together with BAO and SNIa provides an upper limit of $b<0.4$ at 95% c.l. ($b<0.5$ without ACT). Adding a SH0ES-based prior on the Hubble constant gives $b=0.31_{-0.15}^{+0.11}$ and $H_0=69.28\pm 0.56\mathrm{km}/\mathrm{s}/\mathrm{Mpc}$ ($b=0.41_{-018}^{+0.14}$ and $H_0=69.70\pm 0.63\mathrm{km}/\mathrm{s}/\mathrm{Mpc}$ without ACT). Finally, we forecast constraints on $b$ for the full SPT-3G survey, Simons Observatory, and CMB-S4, finding improvements by factors of 1.5 (2.7 with Planck), 5.9 and 7.8, respectively, over Planck alone.

Radial steady-state accretion of polytropic matter is investigated under cylindrical symmetry in the Levi-Civita background metric. The model can be considered as a cylindrical analog of Bondi accretion in a strong gravitational field. As a byproduct of this study, the issue of defining the line mass density is addressed, and the role of the metric free parameters is discussed on the example of physical observables. The form of radial accretion equations is insensitive to the structure of the interior solution. Accordingly, the accretion solution analysis can be limited to a special Wilson form of the Levi-Civita metric describing a structureless homogeneous string.

We report an underlying event tune for the pythia8 Monte Carlo event generator that is applicable for hadron collisions primarily at $\sqrt{s}$ ranges available at the Relativistic Heavy-Ion Collider (RHIC). We compare our new pythia8 tuned predictions to midrapidity inclusive ${\pi }^{\pm }$ spectra, jet substructure, Drell-Yan production, and underlying event measurements from RHIC and the Tevatron, as well as underlying event data from the Large Hadron Collider. With respect to the default pythia8 Monash Tune, the new “Detroit” tune shows significant improvements in the description of the experimental data. Additionally, we explore the validity of pythia8 predictions for forward rapidity $\pi$ in $\sqrt{s}=200\mathrm{GeV}$ collisions, where neither tune is able to sufficiently describe the data. We advocate for the new tune to be used for pythia8 studies at current and future RHIC experiments, and discuss future tuning exercises at lower center-of-mass energies, where forward/backward kinematics are essential at the upcoming Electron-Ion Collider.

Using properties of Goldstino, we show that in generic grand unified theories with gravity-mediated supersymmetry breaking the $\mu$-problem is nonexistent. What happens is that supersymmetry breaking universally induces the shifts of the heavy fields that generate $\mu$ and $B_{\mu }$ terms. In the leading order, these are given by the mass of gravitino and are insensitive to the scale of grand unification. The mechanism works regardless whether doublet-triplet splitting is achieved via fine-tuning or not. Moreover, we illustrate this general phenomenon on explicit examples of theories that achieve doublet-triplet splitting dynamically. These include the theories with Higgs doublet as a pseudo-Goldstone boson, as well as the approach based on spontaneous decoupling of the light color triplet from quarks and leptons.

The LHCb measurements of the $\mu /e$ ratio in $B\to K\ell \ell$ decays $(R_K)$ indicate a deficit with respect to the Standard Model prediction, supporting earlier hints of lepton universality violation observed in the $R_{K^{(*)}}$ ratio. Possible explanations of these $B$-physics anomalies include heavy $Z^{\prime }$ bosons or scalar and vector leptoquarks mediating $b\to s{\mu }^{+}{\mu }^{-}$. We note that a muon collider can directly measure this process via ${\mu }^{+}{\mu }^{-}\to b\overline{s}$ and can shed light on the lepton nonuniversality scenario. Investigating currently discussed center-of-mass energies $\sqrt{s}=3$, 6 and 10 TeV, we show that the parameter space of $Z^{\prime }$ and leptoquark solutions to the $R_{K^{(*)}}$ anomalies can be mostly covered. Effective operators explaining the anomalies can be probed with the muon collider setup $\sqrt{s}=6\mathrm{TeV}$ and integrated luminosity $L=4{\mathrm{ab}}^{-1}$.

This paper investigates the capability of long-baseline experiments, which are making use of neutrinos that are coming from Japan Proton Accelerator Research Complex, in establishing the unitarity of active-neutrino mixing by ruling out the nonunitary mixing scheme as a function of true values of $CP$-violating phase ${\delta }_{CP}$. It is found that T2HK can establish the unitarity of active neutrino mixing at above $2\sigma$ C.L. irrespective of neutrino mass hierarchy and the true value of ${\delta }_{CP}$, if the nonunitary (NU) parameter ${\alpha }_{21}$ is of the order of ${10}^{-2}$. Further, this paper also discusses the bound on the NU parameter in the 21 sector and the sensitivity limit of these experiments in determining the NU parameter. It is found that the bounds on $({\alpha }_{21}/2)$ are 0.028, 0.0026, 0.005 at $2\sigma$ C.L., respectively, for T2K, T2HK, and T2HKK. Moreover, it is also found that the sensitivity limit of T2HK on NU parameter is far better than that of both T2HKK and T2K.

Scenarios in which right-handed light Standard Model fermions couple to a new gauge group, $U(1{)}_{T3R}$, can naturally generate a sub-GeV dark matter candidate. But such models necessarily have large couplings to the Standard Model, generally yielding tight experimental constraints. We show that the contributions to $g_{\mu }-2$ from the dark photon and dark Higgs largely cancel out in the narrow window where all the experimental constraints are satisfied, leaving a net correction that is consistent with recent measurements from Fermilab. These models inherently violate lepton universality, and UV completions of these models can include quark flavor violation that can explain $R_{K^{(*)}}$ anomalies as observed at the LHCb experiment after satisfying constraints on $\mathrm{Br}(B_s\to {\mu }^{+}{\mu }^{-})$ and various other constraints in the allowed parameter space of the model. This scenario can be probed by FASER, SeaQuest, SHiP, LHCb, Belle, etc.

We study the localization properties of the low-lying Dirac eigenmodes in QCD at imaginary chemical potential ${\widehat{\mu }}_I=\pi$ at temperatures above the Roberge-Weiss (RW) transition temperature $T_{\mathrm{RW}}$. We find that modes are localized up to a temperature-dependent “mobility edge” and delocalized above it and that the mobility edge extrapolates to zero at a temperature compatible with $T_{\mathrm{RW}}$. This supports the existence of a strong connection between localization of the low Dirac modes and deconfinement, studied here for the first time in a model with a genuine deconfinement transition in the continuum limit in the presence of dynamical fermions.

The decay $H\to {\ell }^{+}{\ell }^{-}\gamma$, $\ell =e$, $\mu$ receives contributions from $H\to Z[\to {\ell }^{+}{\ell }^{-}]\gamma$ and a nonresonant contribution, both of which are loop induced. We describe how one can separate these subprocesses in a gauge-independent way, define the decay rate $\mathrm{\Gamma }(H\to Z\gamma )$, and extract the latter from differential $H\to {\ell }^{+}{\ell }^{-}\gamma$ branching ratios. For $\ell =\mu$, also the tree decay rate, which is driven by the muon Yukawa coupling, is important. We propose kinematic cuts optimized to separate the three contributions, paving the way to the milestone (i) discovery of $H\to Z\gamma$, (ii) discovery of $H\to {\mu }^{+}{\mu }^{-}{\gamma |}_{\text{tree}}$, and (iii) quantification of new physics in both the effective $H\text{−}Z\text{−}\gamma$ and nonresonant $H\text{−}{\ell }^{+}\text{−}{\ell }^{-}\text{−}\gamma$ couplings.

We report results from a search for the decay $B_s^0\to \eta \eta$ using $121.4{\mathrm{fb}}^{-1}$ of data collected at the $\mathrm{\Upsilon }(5S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^{+}{e}^{-}$ collider. We do not observe any signal and set an upper limit on the branching fraction of $14.3\times {10}^{-5}$ at 90% confidence level. This result represents a significant improvement over the previous most stringent limit.

This paper presents a search for decays of the Higgs boson with a mass of 125 GeV into a pair of new pseudoscalar particles, $H\to aa$, where one $a$-boson decays into a $b$-quark pair and the other into a muon pair. The search uses $139{\mathrm{fb}}^{-1}$ of proton-proton collision data at a center-of-mass energy of $\sqrt{s}=13\mathrm{TeV}$ recorded between 2015 and 2018 by the ATLAS experiment at the LHC. A narrow dimuon resonance is searched for in the invariant mass spectrum between 16 GeV and 62 GeV. The largest excess of events above the Standard Model backgrounds is observed at a dimuon invariant mass of 52 GeV and corresponds to a local (global) significance of $3.3\sigma$ ($1.7\sigma$). Upper limits at 95% confidence level are placed on the branching ratio of the Higgs boson to the $bb\mu \mu$ final state, $\mathcal{B}(H\to aa\to bb\mu \mu )$, and are in the range $0.2–4.0\times {10}^{-4}$, depending on the signal mass hypothesis.

We report the first direct measurement of the inclusive branching fraction $\mathcal{B}(B_s\to D_{s}X)$ via $B_s$ tagging in $e^{+}{e}^{-}\to \mathrm{\Upsilon }(5\mathrm{S})$ events. Tagging is accomplished through a partial reconstruction of semileptonic decays $B_s\to D_{s}X\ell \nu$, where $X$ denotes unreconstructed additional hadrons or photons and $\ell$ is an electron or muon. With $121.4{\mathrm{fb}}^{-1}$ of data collected at the $\mathrm{\Upsilon }(5\mathrm{S})$ resonance by the Belle detector at the KEKB asymmetric-energy $e^{+}{e}^{-}$ collider, we obtain $\mathcal{B}(B_s\to D_{s}X)=(60.2\pm 5.8\pm 2.3)\%$, where the first uncertainty is statistical and the second is systematic.

We present a measurement of the branching fractions of the Cabibbo favored ${\overline{B}}^0\to D^{+}{\pi }^{-}$ and the Cabibbo suppressed ${\overline{B}}^0\to D^{+}{K}^{-}$ decays. We find $\mathcal{B}({\overline{B}}^0\to D^{+}{\pi }^{-})=(2.48\pm 0.01\pm 0.09\pm 0.04)\times {10}^{-3}$ and $\mathcal{B}({\overline{B}}^0\to D^{+}{K}^{-})=(2.03\pm 0.05\pm 0.07\pm 0.03)\times {10}^{-4}$ decays, where the first uncertainty is statistical, the second is systematic, and the third uncertainty is due to the $D^{+}\to K^{-}{\pi }^{+}{\pi }^{+}$ branching fraction. The ratio of branching fractions of ${\overline{B}}^0\to D^{+}{K}^{-}$ and ${\overline{B}}^0\to D^{+}{\pi }^{-}$ is measured to be $R^D=[8.19\pm 0.20(\mathrm{stat})\pm 0.23(\mathrm{syst})]\times {10}^{-2}$. These measurements are performed using the full Belle dataset, which corresponds to $772\times {10}^{6}B\overline{B}$ pairs and use the Belle II software framework for data analysis.

In this Letter, we introduce the nonlinear partial differential equation ${\partial }_{\tau }^2\pi \propto (\overrightarrow{\nabla }\pi {)}^2$ showing a new type of instability. Such equations appear in the effective field theory (EFT) of dark energy for the $k$-essence model as well as in many other theories based on the EFT formalism. We demonstrate the occurrence of instability in the cosmological context using a relativistic $N$-body code, and we study it mathematically in $3+1$ dimensions within spherical symmetry. We show that this term dominates for the low speed of sound limit where some important linear terms are suppressed.

We define a bulk wormhole geometry interpolating between horizons of differing size and determine characteristics of the Hubeny-Rangamani-Takayanagi surface in these geometries. This construction is dual to black hole mesostates, an intermediate coarse-graining of states between black hole microstates and the full black hole state. We analyze the distinguishability of these objects using the recently derived holographic Holevo information techniques, demonstrating novel phase transition behavior for such systems.

In this paper we consider some new classical effects obtained for a planar electrodynamics with the presence of a higher order derivatives term. The model can be interpreted as a kind of extension for the $3d$ Maxwell-Chern-Simons electrodynamics with higher order derivatives. We consider setups with stationary field sources describing pointlike charges and Dirac points. We also investigate this model with the presence of a conducting line (in $3d$ dimensions, it is the equivalent of a conducting plate in $4d$ dimensions). In this case we calculate the propagator for the gauge field and the interaction force between the conducting line and a pointlike charge, as well as the force between the conducting line and a Dirac point, the source for vortex field solutions. It is shown that the image method is not valid in any case. We also compare the obtained results along the paper with the corresponding ones obtained with the standard Maxwell-Chern-Simons electrodynamics [L. H. C. Borges et al., Eur. Phys. J. C 80, 238 (2020)].

We consider necessary and sufficient conditions for photons emitted from an arbitrary spacetime position of the extremal Kerr black hole to escape to infinity. The radial equation of motion determines the necessary conditions for photons emitted from $r=r_{*}$ to escape to infinity, and the polar angle equation of motion further restricts the allowed region of photon motion. From these two conditions, we provide a method to visualize a two-dimensional photon impact parameter space that allows photons to escape to infinity, i.e., the escapable region. Finally, we completely identify the escapable region for the extremal Kerr black hole spacetime. This study has generalized our previous result [K. Ogasawara and T. Igata, Phys. Rev. D 103, 044029 (2021)], which focused only on light sources near the horizon, to the classification covering light sources in the entire region.

Many experiments have recently been proposed to test whether nonrelativistic gravitational interactions can generate entanglement. In this paper, I consider the extent to which these experiments can test if the graviton exists. Assuming unitarity and Lorentz invariance of the $S$-matrix, I demonstrate that this “Newtonian entanglement” requires the existence of massless bosons, universally coupled to mass, in the Hilbert space of low-energy scattering states. These bosons could be the usual spin-2 gravitons, but in principle there are other possibilities like spin-0 scalar gravitons. I suggest a concept for a more refined experiment to rule these out. The special role of $d=3+1$ spacetime dimensions and the possibility that unitarity is violated by gravity are highlighted.

We present a wave generalization of the classic Schwarzschild method for constructing self-consistent halos—such a halo consists of a suitable superposition of waves instead of particle orbits, chosen to yield a desired mean density profile. As an illustration, the method is applied to spherically symmetric halos. We derive an analytic relation between the particle distribution function and the wave superposition amplitudes and show how it simplifies in the high-energy (WKB) limit. We verify the stability of such constructed halos by numerically evolving the Schrödinger-Poisson system. The algorithm provides an efficient and accurate way to simulate the time-dependent halo substructures from wave interference. We use this method to construct halos with a variety of density profiles, all of which have a core from the ground-state wave function, though the core-halo relation need not be the standard one.