Recently, the ATLAS and CMS Collaborations reported the latest experimental upper limits on the branching ratios of the lepton flavor violating (LFV) 125 GeV Higgs boson decays, $h\to e\mu$, $h\to e\tau$, and $h\to \mu \tau$. In this paper, we mainly investigate the LFV Higgs boson decays $h\to e\mu$, $h\to e\tau$, and $h\to \mu \tau$ in the minimal supersymmetric extension of the Standard Model with local $B-L$ gauge symmetry. At the same time, the corresponding constraints from the LFV rare decays $\mu \to e\gamma$, $\tau \to e\gamma$, $\tau \to \mu \gamma$, and muon ($g-2$) are considered to analyze the numerical results.

Motivated by searches for $0\nu \beta \beta$ decay in nuclear experiments and collider probes of lepton number violation at dimension $d\ge 7$, we investigate the sensitivity to the $d=5$ Weinberg operator using the nonresonant signature $pp\to {\ell }^{\pm }{{\ell }^{\prime }}^{\pm }jj$ at the LHC. We develop a prescription for the operator that is applicable in collisions and decays, and focus on the $\ell {\ell }^{\prime }=\mu \mu$ channel, which is beyond the reach of nuclear decays. For a Wilson coefficient $C_5^{\mu \mu }=1$, scales as heavy as $\mathrm{\Lambda }\sim 8.3(11)\mathrm{TeV}$ can be probed with $\mathcal{L}=300{\mathrm{fb}}^{-1}(3{\mathrm{ab}}^{-1})$. This translates to an effective $\mu \mu$ Majorana mass of $|m_{\mu \mu }|\sim 7.3(5.4)\mathrm{GeV}$ and establishes a road map for testing the Weinberg operator at accelerators.

We provide five benchmark hidden valley models with perturbative parton showers, which span a wide range of dark shower phenomenology. We consider production through an $s$-channel, heavy mediator, which can be identified with the SM Higgs. By assuming a set of well-motivated decay portals, one can moreover fix both the branching ratios of the dark mesons and set a lower bound on their lifetime. We provide a public python tool which can be used to generate self-consistent pythia 8 cards for our benchmark models.

We study the operator product expansion of stress tensors ($TT$ OPE) in $d>2$ conformal field theories whose bulk dual is Einstein gravity. Directly from the $TT$ OPE, we obtain, in a certain null-like limit, an algebraic structure consistent with the Jacobi identity: $[{\mathcal{L}}_m,{\mathcal{L}}_n]=(m-n){\mathcal{L}}_{m+n}+Cm(m^2-1){\delta }_{m+n,0}$. The dimensionless constant $C$ is proportional to the central charge $C_T$. Transverse integrals in the definition of ${\mathcal{L}}_m$ play a crucial role. We comment on the corresponding limiting procedure and point out a curiosity related to the central term. A connection between the $d>2$ near-lightcone stress-tensor conformal block and the $d=2$ $\mathcal{W}$ algebra is observed. This note is motivated by the search for a field-theoretic derivation of $d>2$ correlators in strong coupling critical phenomena.

We discuss a mechanism where charged lepton masses are derived from one-loop diagrams mediated by particles in a dark sector including a dark matter candidate. We focus on a scenario where the muon and electron masses are generated at one loop with new $\mathcal{O}(1)$ Yukawa couplings. The measured muon anomalous magnetic dipole moment, $(g-2{)}_{\mu }$, can be explained in this framework. As an important prediction, the muon and electron Yukawa couplings can deviate significantly from their standard model predictions, and such deviations can be tested at High-Luminosity LHC and future $e^{+}{e}^{-}$ colliders.

In this paper we consider aspects of the holographic interpretation of Taub-NUT-${\mathrm{AdS}}_4$. We review our earlier results which show that ${\mathrm{TNAdS}}_4$ gives rise to a holographic three-dimensional conformal fluid having constant vorticity. We then study the holographic relevance of the Misner string by considering bulk scalar fluctuations. The scalar fluctuations organize naturally into representations of the $SU(2)\times \mathbb{R}$ isometry algebra. If we require the string’s invisibility we obtain a Dirac-like quantization relating the frequency of the scalar field modes to the NUT charge. As the latter quantity determines the total vorticity flux of the boundary fluid, we argue that such an assumption allows for a holographic interpretation of ${\mathrm{TNAdS}}_4$ as a nondissipative superfluid whose excitations are quantized vortices. Alternatively, if we regard the Misner string as a physical object, as has recently been advocated for thermodynamically, the aforementioned quantization conditions are removed, and we find that ${\mathrm{TNAdS}}_4$ corresponds to a holographic fluid whose dissipative properties are probed as usual by the complex quasinormal modes of the bulk fluctuations. We show that such quasinormal modes are, perhaps surprisingly, organized into infinite-dimensional nonunitary representations of the isometry algebra.

We study gravitini zero modes in four dimensional $\mathcal{N}=2$ pure supergravity theory. The gravitini zero modes we study are solutions to the Rarita-Schwinger equations of motion in the background of the purely bosonic Majumdar-Papapetrou background. We start with a very generic ansatz for the gravitini that involves 32 ansatz functions and reduce the Rarita-Schwinger equations to a set of linear coupled partial differential equations on ${\mathbf{R}}^3$: the kind familiar from electromagnetism with divergences, curls, etc. We first show how the gravitini zero modes due to broken supersymmetries arise in this setup and how they solve the equations on ${\mathbf{R}}^3$. Then we go on and obtain other solutions to these equations: the “extra” fermion zero modes, parametrized by four integration constants (one of the integration constants corresponds to the gravitini zero modes due to broken supersymmetries). A careful analysis of pure gauge solutions reveals that we have four independent extra zero modes.

A covariant formulation for the Newton-Hooke particle is presented by following an algorithm developed by us R. Banerjee et al. [Phys. Lett. B 737, 369 (2014); Classical Quantum Gravity 32, 045010 (2015); Phys. Rev. D 91, 084021 (2015)]. It naturally leads to a coupling with the Newton-Cartan geometry. From this result we provide an understanding of gravitation in a Newtonian geometric background. Using Dirac’s constrained analysis a canonical formulation for the Newton-Hooke covariant action is done in both gauge independent and gauge fixed approaches. While the former helps in identifying the various symmetries of the model, the latter is able to define the physical variables. From this analysis a path to canonical quantization is traced and the Schroedinger equation is derived which is shown to satisfy various consistency checks. Some consequences of this equation are briefly mentioned.

We present a new study of remnant black hole properties from 13 binary black hole systems, numerically evolved using the Spectral Einstein Code. The mass, spin, and recoil velocity of each remnant were determined quasilocally from apparent horizon data and asymptotically from Bondi data $(h,{\psi }_4,{\psi }_3,{\psi }_2,{\psi }_1)$ computed at future null infinity using SpECTRE’s Cauchy characteristic evolution. We compare these independent measurements of the remnant properties in the bulk and on the boundary of the spacetime, giving insight into how well asymptotic data are able to reproduce local properties of the remnant black hole in numerical relativity. We also discuss the theoretical framework for connecting horizon quantities to asymptotic quantities and how it relates to our results. This study recommends a simple improvement to the recoil velocities reported in the Simulating eXtreme Spacetimes waveform catalog, provides an improvement to future surrogate remnant models, and offers new analysis techniques for evaluating the physical accuracy of numerical simulations.

We consider the scenario that the effective gravitational Lagrangian of a minimally coupled scalar field at large curvatures is described by a rescaled Einstein-Hilbert gravity, with the Ricci scalar being multiplied by a dimensionless parameter $\alpha$. Such Lagrangian densities might originate, for example, by a class of exponential models of $f(R)$ gravity, in the presence of a canonical scalar field, for which at early times the effective Lagrangian of the theory becomes that of a rescaled canonical scalar field with the Einstein-Hilbert term becoming $\sim \alpha R$, with $\alpha$ a dimensionless constant, and the resulting theory is an effective theory of a Jordan frame $f(R,\varphi )$ theory. This rescaled Einstein-Hilbert canonical scalar field theory at early times has some interesting features, since it alters the inflationary phenomenology of well-known scalar field models of inflation, but more importantly, in the context of this rescaled theory, the swampland criteria are easily satisfied, assuming that the scalar field is slowly rolling. We consider two models of inflation to exemplify our study, a fiber inflation model and a model that belongs to the general class of supergravity $\alpha$-attractor models. The inflationary phenomenology of the models is demonstrated to be viable, and for the same set of values of the free parameters of each model which ensure their inflationary viability, all the known swampland criteria are satisfied too, and we need to note that we assumed that the first swampland criterion is marginally satisfied by the scalar field, so $\varphi \sim M_p$ during the inflationary era. Finally, we examine the late-time phenomenology of the fiber inflation potential in the presence of the full $f(R)$ gravity, and we demonstrate that the resulting model produces a viable dark energy era, which resembles the $\mathrm{\Lambda }$-cold-dark-mater model. Thus, in the modified gravity model we present, the Universe is described by a rescaled Einstein-Hilbert gravity at early times; hence, in some sense, the modified gravity effect is minimal primordially, and the scalar field controls mainly the dynamics with a rescaled Ricci scalar gravity. However, the effect of $f(R)$ gravity becomes stronger at late times, where it controls the dynamics, synergistically with the scalar field.

Non-singular black hole geometries typically come with two spacetime horizons: an (outer) event horizon and an (inner) Cauchy horizon. This nurtures the speculation that they may be subject to a mass-inflation effect which renders the Cauchy horizon unstable. We analyze the dynamics associated with spherically symmetric, regular black holes taking the full backreaction between the infalling matter and geometry into account. On this basis, we identify the crucial features taming the growth of the mass function and diminishing the curvature singularity at the Cauchy horizon. It is demonstrated explicitly that the regular black hole solutions proposed by Hayward and obtained from Asymptotic Safety satisfy these properties.

Binary black holes with misaligned spins will generically induce both precession and nutation of the orbital angular momentum $\mathbf{L}$ about the total angular momentum $\mathbf{J}$. These phenomena modulate the phase and amplitude of the gravitational waves emitted as the binary inspirals to merger. We introduce a “taxonomy” of binary black-hole spin precession that encompasses all the known phenomenology, then present five new phenomenological parameters that describe generic precession and constitute potential building blocks for future gravitational waveform models. These are the precession amplitude $⟨{\theta }_L⟩$, the precession frequency $⟨{\mathrm{\Omega }}_L⟩$, the nutation amplitude $\mathrm{\Delta }{\theta }_L$, the nutation frequency $\omega$, and the precession-frequency variation $\mathrm{\Delta }{\mathrm{\Omega }}_L$. We investigate the evolution of these five parameters during the inspiral and explore their statistical properties for sources with isotropic spins. In particular, we find that nutation of $\mathbf{L}$ is most prominent for binaries with high spins ($\chi \gtrsim 0.5$) and moderate mass ratios ($q\sim 0.6$).

We present a new family of exact black hole configurations, which is a solution to a generalized Einstein-Maxwell-Dilaton setup in arbitrary dimension. These solutions are asymptotically Lifshitz for any dynamical critical exponent $z\ge 1$. It turns out that the existence of a nontrivial scalar field is a direct consequence of breaking the spacetime isotropic scaling symmetry. This black hole family accepts various interesting limits that link it to well-known solutions in both the isotropic and anisotropic cases. We study the thermodynamics of these field configurations showing that the first law is satisfied and providing the corresponding Smarr formula, both of these relations account for an electric contribution. Furthermore, we show that for a certain parameter region, the anisotropic field configuration with a nonzero scalar field is thermodynamically preferred. This observation, together with a direct verification of the so-called scalarization conditions, suggest that the emergence of the dilaton field is due to a mechanism similar to spontaneous scalarization.

We consider a spherically symmetric line element which admits either a black hole geometry or a wormhole geometry and show that in both cases the apparent horizon or the wormhole throat is partially characterized by the zero set of a single curvature invariant. The detection of the apparent horizon by this invariant is consistent with the geometric horizon detection conjectures and implies that it is a geometric horizon of the black hole, while the detection of the wormhole throat presents a conceptual problem for the conjectures. To distinguish between these surfaces, we determine a set of curvature invariants that fully characterize the apparent horizon and wormhole throat. Motivated by this result, we introduce the concept of a geometric surface as a generalization of a geometric horizon and extend the geometric horizon detection conjectures to geometric surfaces. As an application, we employ curvature invariants to characterize three important surfaces of the line element introduced by Simpson, Martin-Moruno, and Visser, which describes transitions between regular Vaidya black holes, traversable wormholes, and black bounces.

In binary-black-hole systems where the black-hole spins are misaligned with the orbital angular momentum, precession effects leave characteristic modulations in the emitted gravitational waveform. Here, we investigate where in the parameter space we will be able to accurately identify precession, for likely observations over coming LIGO-Virgo-KAGRA observing runs. Despite the large number of parameters that characterize a precessing binary, we perform a large scale systematic study to identify the impact of each source parameter on the measurement of precession. We simulate a fiducial binary at moderate mass-ratio, signal-to-noise ratio (SNR), and spins, such that precession will be clearly identifiable, then successively vary each parameter while holding the remaining parameters fixed. As expected, evidence for precession increases with signal-to noise-ratio (SNR), higher in-plane spins, more unequal component masses, and higher inclination, but our study provides a quantitative illustration of each of these effects, and informs our intuition on parameter dependencies that have not yet been studied in detail, for example, the effect of varying the relative strength of the two polarizations, the total mass, and the aligned-spin components. We also measure the “precession SNR” ${\rho }_p$, to quantify the signal power associated with precession. By comparing ${\rho }_p$ with both Bayes factors and the recovered posterior distributions, we find it is a reliable metric for measurability that accurately predicts when the detected signal contains evidence for precession.

We study gravity wave production and baryogenesis at the electroweak phase transition in a real singlet scalar extension of the Standard Model, including vectorlike top partners, to generate the $CP$ violation needed for electroweak baryogenesis (EWBG). The singlet makes the phase transition strongly first order through its coupling to the Higgs boson, and it spontaneously breaks $CP$ invariance through a dimension-five contribution to the top quark mass term, generated by integrating out the heavy top quark partners. We improve on previous studies by incorporating updated transport equations, compatible with large bubble wall velocities. The wall speed and thickness are computed directly from the microphysical parameters rather than treating them as free parameters, allowing for a first-principles computation of the baryon asymmetry. The size of the $CP$-violating dimension-five operator needed for EWBG is constrained by collider, electroweak precision, and renormalization group running constraints. We identify regions of parameter space that can produce the observed baryon asymmetry or observable gravitational wave (GW) signals. Contrary to standard lore, we find that for strong deflagrations, the efficiencies of large baryon asymmetry production and strong GW signals can be positively correlated. However, we find the overall likelihood of observably large GW signals to be smaller than estimated in previous studies. In particular, only detonation-type transitions are predicted to produce observably large gravitational waves.

We study a phenomenological class of models where dark matter converts to dark radiation in the low redshift epoch. This class of models, dubbed DMDR, characterizes the evolution of comoving dark-matter density with two extra parameters, and may be able to help alleviate the observed discrepancies between early and late-time probes of the Universe. We investigate how the conversion affects key cosmological observables such as the cosmic microwave background (CMB) temperature and matter power spectra. Combining 3x2pt data from Year 1 of the Dark Energy Survey, Planck-2018 CMB temperature and polarization data, supernovae (SN) Type Ia data from Pantheon, and baryon acoustic oscillation (BAO) data from BOSS DR12, MGS and 6dFGS, we place new constraints on the amount of dark matter that has converted to dark radiation and the rate of this conversion. The fraction of the dark matter that has converted since the beginning of the Universe in units of the current amount of dark matter, $\zeta$, is constrained at 68% confidence level to be $<0.32$ for DES-Y1 3x2pt data, $<0.030$ for $\mathrm{CMB}+\mathrm{SN}+\mathrm{BAO}$ data, and $<0.037$ for the combined dataset. The probability that the DES and CMB+SN+BAO datasets are concordant increases from 4% for the $\mathrm{\Lambda }\mathrm{CDM}$ model to 8% (less tension) for DMDR. The tension in $S_8={\sigma }_8\sqrt{{\mathrm{\Omega }}_m/0.3}$ between DES-Y1 3x2pt and $\mathrm{CMB}+\mathrm{SN}+\mathrm{BAO}$ is slightly reduced from $2.3\sigma$ to $1.9\sigma$. We find no reduction in the Hubble tension when the combined data is compared to distance-ladder measurements in the DMDR model. The maximum-posterior goodness-of-fit statistics of DMDR and $\mathrm{\Lambda }\mathrm{CDM}$ model are comparable, indicating no preference for the DMDR cosmology over $\mathrm{\Lambda }\mathrm{CDM}$.

With the entrance of cosmology in its new era of high precision experiments, low- and high-redshift observations set off tensions in the measurements of both the present-day expansion rate ($H_0$) and the clustering of matter ($S_8$). We provide a simultaneous explanation of these tensions using the Parker-Raval vacuum metamorphosis (VM) model with the neutrino sector extended beyond the three massless Standard Model flavors and the curvature of the universe considered as a model parameter. To estimate the effect on cosmological observables we implement various extensions of the VM model in the standard cosmomc pipeline and establish which regions of parameter space are empirically viable to resolve the $H_0$ and $S_8$ tensions. We constrain the parameter space employing the following datasets: (i) the cosmic microwave temperature and polarization data from the Planck mission, (ii) baryon acoustic oscillations (BAO) measurements, and (iii) the Pantheon sample of Supernovae type Ia. We find that the likelihood analyses of the physically motivated VM model, which has the same number of free parameters as in the spatially flat $\mathrm{\Lambda }\mathrm{CDM}$ model, always gives $H_0$ in agreement with the local measurements (even when BAO or Pantheon data are included) at the price of much larger ${\chi }^2$ than $\mathrm{\Lambda }\mathrm{CDM}$. The inclusion of massive neutrinos and extra relativistic species quantified through two well-known parameters $\sum m_{\nu }$ and $N_{\mathrm{eff}}$, does not modify this result, and in some cases improves the goodness of the fit. In particular, for the original $\mathrm{VM}+\sum m_{\nu }+N_{\mathrm{eff}}$ and the Planck+BAO+Pantheon dataset combination, we find evidence for $\sum m_{\nu }=0.80_{-0.22}^{+0.18}\mathrm{eV}$ at more than $3\sigma$, no indication for extra neutrino species, $H_0=71.0\pm 1.2\mathrm{km}/\mathrm{s}/\mathrm{Mpc}$ in agreement with local measurements, and $S_8=0.755\pm 0.032$ that solves the tension with the weak lensing measurements.

An optical equation for null strings is derived. The equation is similar to Sachs’s optical equations for null geodesic congruences. The string optical equation is given in terms of a single complex scalar function $Z$, which is a combination of spin coefficients at the string trajectory. Real and imaginary parts of $Z$ determine the expansion and rotation of strings. Trajectories of strings can be represented by diagrams in a complex $Z$ plane. Such diagrams allow one to draw some universal features of null strings in different backgrounds. For example, in asymptotically flat space-times $Z$ vanishes as future null infinity is approached, that is, gradually shapes of strings are “freezing out.” Outgoing gravitational radiation and flows of matter leave ripples on the strings. These effects are encoded in subleading terms of $Z$. String diagrams are demonstrated for rotating and expanding strings in a flat space-time and in cosmological models.

Testing a subset of viable cosmological models beyond general relativity, with implications for cosmic acceleration and the dark energy associated with it, is within the reach of Rubin Observatory Legacy Survey of Space and Time (LSST) and a part of its endeavor. Deviations from $\mathrm{GR}\text{−}w(z)\mathrm{CDM}$ models can manifest in the growth rate of structure and lensing, as well as in screening effects on nonlinear scales. We explore the constraining power of small-scale deviations predicted by the $f(R)$ Hu-Sawicki modified gravity candidate, by emulating this model with COLA (comoving Lagrangian acceleration) simulations. We present the experimental design, data generation, and interpolation schemes in cosmological parameters and across redshifts for the emulation of the boost in the power spectra due to modified gravity effects. Three preliminary applications of the emulator highlight the sensitivity to cosmological parameters, Fisher forecasting and Markov chain Monte Carlo inference for a fiducial cosmology. This emulator will play an important role for future cosmological analysis handling the formidable amount of data expected from Rubin Observatory LSST.