Focusing on four-Higgs interactions, we analyze the robustness of tree-level-derived positivity bounds on standard model effective field theory (SMEFT) operators under quantum corrections. Among other results, we demonstrate that: (i) Even in the simplest extensions of the Standard Model, e.g., with one new scalar singlet or with a neutral triplet, some positivity bounds are strictly violated; (ii) the mixing of the dimension-eight operators under renormalization, which we compute here for the first time, can drive them out of their positivity region; (iii) the running of the dimension-eight interactions triggered by solely dimension-six terms respects the positivity bounds. Our results suggest, on one hand, that departures from positivity within the SMEFT, if ever found in the data, do not necessarily imply the breaking of unitarity or causality, nor the presence of new light degrees of freedom. On the other hand, they lead to strong constraints on the form of certain anomalous dimensions.

We use the gauge/gravity correspondence to show that in its context there appear Landau levels when studying the excitations of the fundamental degrees of freedom of a strongly coupled plasma subject to a magnetic field of arbitrary intensity. We work in the phase where mesons are melted by embedding a D7-brane in the 10D uplift that we construct for the 5D background associated with a magnetic brane. By studying the dependence of the lowest quasinormal frequency on both the intensity of the magnetic field and the Landau level, we corroborate that the energy behaves as expected for dissociating Landau levels. The reconstruction of the impact of the magnetic field on the stability of the quasinormal modes allows us to identify inverse magnetic catalysis for intensities of the field below a certain value and magnetic catalysis for those above it.

We investigate the circuit complexity and Loschmidt echo for the (inverted) harmonic oscillators. Using a perturbative approach, we analytically derive the Lyapunov exponent and scrambling time of the inverted harmonic oscillators. We show that the circuit complexity and Loschmidt echo exhibit qualitatively similar behaviors, particularly the consistent Lyapunov exponent.

We study the phase diagram of (large-$N_c$) QCD using a simplistic holographic hard-wall model with a dynamical scalar field and a homogeneous Ansatz representing a smeared instanton/baryon density. The resulting phase diagram is qualitatively consistent with expectations, including a mesonic, baryonic, quarkyonic, and quark-gluon plasma phase. As in other holographic models, we also find a baryonic popcorn transition, which appears at large chemical potential as a crossover. We then evaluate the nuclear matter equation of state, which turns out to be rather stiff with a large peaked sound velocity above the conformal limit, construct corresponding neutron stars using the Tolman-Oppenheimer-Volkov equations, and finally use a full numerical gravity/hydrodynamics computation to extract the gravitational wave signal of neutron star mergers.

Gauge coupling unification misleads infrared observers if new gauge bosons do not simultaneously come into the spectrum. Though easy to engineer in gauge theory, the situation in string theory is nuanced due to moduli dependence. We study the possibility of faking gauge coupling unification in the context of 4D F-theory compactifications. Specifically, we formulate a sufficient condition that we call a strong calibration, under which seven-brane gauge couplings on homologically distinct divisors become equal at codimension one in Kähler moduli space. We prove that a strong calibration is preserved under appropriate topological transitions and that a pair of nonintersecting divisors each admitting a contraction can always be strongly calibrated. Within the tree ensemble [J. Halverson et al., Phys. Rev. D 96, 126006 (2017)], we find that $\approx 77.12\%$ of pairs of intersecting toric divisors can be strongly calibrated and $\approx 3.22\%$ can never be calibrated. Physically, this means that gauge coupling unification can be faked in most cases that we study, but in others it can not, which is surprising from a gauge theoretic perspective.

A unified multiscalar field model with three flat regions is discussed. The three flat regions are the inflation, early- and late dark energy epochs. The potential is obtained by a spontaneous breaking of scale invariance generated by non-Riemannian measures of integration (or two measures theories (TMT)). We define the scale invariant couplings of the scalar fields to the different measures through exponential potentials. Spontaneous breaking of scale invariance takes place when integrating the fields that define the measures. When going to the Einstein frame we obtain: (i) An effective potential for the scalar fields with three flat regions which allows for a unified description of both early Universe inflation (in the higher-energy density flat region) as well as of present dark energy epoch which can be realized with a double phase, i.e., in two flat regions. (ii) In the slow-roll inflation, only one field combination, the “dilaton,” which transforms under scale transformations, has nontrivial dynamics; the orthogonal one, which is scale invariant, remains constant. The corresponding perturbations of the dilaton are calculated. (iii) For a reasonable choice of the parameters the present model perturbations conforms to the Planck Collaboration data. (iv) In the late Universe we define scale-invariant couplings of Dark Matter to the dilaton. These couplings define a matter-induced potential for the dilaton and extremizing this potential determines the scale-invariant scalar field, while all exotic noncanonical behavior of the Dark Matter as well as any possible fifth force disappear. (v) We calculate the evolution of the late Universe under these conditions with the realization of two different possible realizations of $\mathrm{\Lambda }$ cold dark matter-type scenarios depending on the flat region in the late Universe. These two phases could appear at different times in the history of the Universe. (vi) From the Planck data, we find the constraints on the parameters during the inflationary epoch and these values are used to obtain constraints relevant to the present epoch.

Motivated by recent activities in Lorentzian Taub-NUT space thermodynamics, we calculate conserved charges of these spacetimes. We find additional mass, nut, angular momentum, and electric and magnetic charge densities distributed along the Misner string. These additional charges are needed to account for the difference between the values of the above charges at horizon and at infinity. We propose an unconstrained thermodynamical treatment for Taub-NUT spaces, where we introduce the nut charge $n$ as a relevant thermodynamic quantity with its chemical potential ${\varphi }_n$. The internal energy in this treatment is $M-n{\varphi }_n$ rather than the mass $M$. This approach leads to an entropy that is a quarter of the area of the horizon and all thermodynamic quantities satisfy the first law, Gibbs-Duhem relation as well as Smarr’s relation. We found a general form of the first law where the quantities depend on an arbitrary parameter. Demanding that the first law is independent of this arbitrary parameter or invariant under electric-magnetic duality leads to a unique form that depends on Misner string electric and magnetic charges. Misner string charges play an essential role in the first law, and without them the first law is not satisfied.

As is well known, asymptotically flat, static, and spherically symmetric black holes do not admit stable bound orbits of massive or massless particles outside the horizon in higher-dimensional Einstein gravity. However, for massive particles, this dramatically changes in higher curvature theories. We clarify the parameter range such that there exist stable bound orbits in $d$-dimensional Einstein-Gauss-Bonnet theories for $6\le d\le 9$. In particular, we show the existence of the lower bound of the Gauss-Bonnet coupling constant below which stable bound orbits cease to exist. Moreover, we also find that for AdS black holes in the theories, there can exist two stable circular orbits outside the horizon.

The information loss paradox is widely regarded as one of the biggest open problems in theoretical physics. Several classical and quantum features must be present to enable its formulation. First, an event horizon is needed to justify the objective status of tracing out degrees of freedom inside the black hole. Second, evaporation must be completed (or nearly completed) in finite time according to a distant observer, and thus the formation of the black hole should also occur in finite time. In spherical symmetry these requirements constrain the possible metrics strongly enough to obtain a unique black hole formation scenario and match their parameters with the semiclassical results. However, the two principal generalizations of surface gravity, the quantity that determines the Hawking temperature, do not agree with each other on the dynamic background. Neither can correspond to the emission of nearly-thermal radiation. We infer from this that the information loss problem cannot be consistently posed in its standard form.

The post-Newtonian dynamics of black hole binaries in Einstein-scalar-Gauss-Bonnet theories of gravity depends on the so-called “sensitivities”; quantities which characterize a black hole’s adiabatic response to the time-dependent scalar field environment sourced by its companion. In this work, we calculate numerically the sensitivities of nonrotating black holes, including spontaneously scalarized ones, in three classes of Einstein-scalar-Gauss-Bonnet gravity: the shift-symmetric, dilatonic, and Gaussian theories. When possible, we compare our results against perturbative analytical results, finding excellent agreement. Unlike their general relativistic counterparts, black holes in Einstein-scalar-Gauss-Bonnet gravity only exist in a restricted parameter space controlled by the theory’s coupling constant. A preliminary study of the role played by the sensitivities in black hole binaries suggests that, in principle, black holes can be driven outside of their domain of existence during the inspiral, for binary parameters which we determine.

We build a model in which the relic abundance of axions is altered from the standard misalignment mechanism, either increased or decreased, due to the presence of a new light scalar that couples to the radial part of the Peccei-Quinn (PQ) field. The light scalar makes the effective PQ symmetry-breaking scale dynamical, altering the early-time dynamics for the axion and affecting its late-time dark matter abundance. We analyze this new mechanism semianalytically and numerically, showing that we can accommodate both lighter or heavier axion dark matter, compared to the standard treatments. We discuss implications of the model for axion searches and fundamental physics.

As cosmological data have improved, tensions have arisen. One such tension is the difference between the locally measured Hubble constant $H_0$ and the value inferred from the cosmic microwave background (CMB). Interacting radiation has been suggested as a solution, but studies show that conventional models are precluded by high-$\ell$ CMB polarization data. It seems at least plausible that a solution may be provided by related models that distinguish between high- and low-$\ell$ multipoles. When interactions of strongly-coupled radiation are mediated by a force carrier that becomes nonrelativistic, the dark radiation undergoes a “step” in which its relative energy density increases as the mediator deposits its entropy into the lighter species. If this transition occurs while CMB-observable modes are inside the horizon, high- and low-$\ell$ peaks are impacted differently, corresponding to modes that enter the horizon before or after the step. These dynamics are naturally packaged into the simplest supersymmetric theory, the Wess-Zumino model, with the mass of the scalar mediator near the eV scale. We investigate the cosmological signatures of such Wess-Zumino dark radiation (WZDR) and find that it provides an improved fit to the CMB alone, favoring larger values of $H_0$. If supernovae measurements from the SH0ES Collaboration are also included in the analysis, the inferred value of $H_0$ is yet larger, but the preference for dark radiation and the location of the transition is left nearly unchanged. Utilizing a standardized set of measures, we compare to other models and find that WZDR is among the most successful at addressing the $H_0$ tension and is the best of those with a Lagrangian formulation.

We present an investigation on the production of light dark gauge bosons by the nucleon bremsstrahlung processes in the core of neutron stars. The dark vector is assumed to be a $U(1{)}_{B-L}$ gauge boson with a mass much below keV. We calculate the emission rate of the dark vector produced by the nucleon bremsstrahlung in the degenerate nuclear matter. In addition, we take into account the photon-dark vector conversion for the photon luminosity observed at infinity. Combining with the observation of J1856 surface luminosity, we find that a recently discovered excess of J1856 hard x-ray emission in the 2–8 keV energy range by X-ray Multi-Mirror Mission-Newton and Chandra x-ray telescopes could be consistently explained by a dark vector with gauge coupling $e^{\prime }=5.56\times {10}^{-15}$, mixing angle $ϵ=1.29\times {10}^{-9}$, and mass $m_{{\gamma }^{\prime }}\lesssim {10}^{-5}\mathrm{eV}$. We also show that the mixing angle $ϵ>7.97\times {10}^{-9}$ for $m_{{\gamma }^{\prime }}\lesssim 3\times {10}^{-5}\mathrm{eV}$ and the gauge coupling $e^{\prime }>4.13\times {10}^{-13}$ for $m_{{\gamma }^{\prime }}\lesssim 1\mathrm{keV}$ have been excluded at 95% confidence level by the J1856 surface luminosity observation. Our best-fit dark vector model satisfies the current limits on hard x-ray intensities from the Swift and INTEGRAL hard x-ray surveys. Future hard x-ray experiments such as the Nuclear Spectroscopic Telescope Array may give a further test on our model.

Motivated by recent indications that the rates of color-allowed nonleptonic channels are not in agreement with their Standard Model expectations based on QCD factorization, we investigate the potential to study $CP$ asymmetries with these decays. In the Standard Model, these flavor-specific decays are sensitive to $CP$ violation in $B_{(s)}^0–{\overline{B}}_{(s)}^0$ mixing, which is predicted with low uncertainties and can be measured precisely with semileptonic decays. Allowing beyond Standard Model (BSM) contributions to the nonleptonic decay amplitudes, we derive explicit expressions for the flavor-specific $CP$ asymmetries in a model-independent way. We find that BSM contributions could lead to significant enhancements to the $CP$ asymmetries. Therefore measurements of these quantities and subsequent comparison with the $CP$ asymmetries measured with semileptonic decays have potential to identify BSM effects without relying on Standard Model predictions that might be affected by hadronic effects. In addition, we discuss the experimental prospects, and note the excellent potential for a precise determination of the $CP$ asymmetry in ${\overline{B}}_s\to D_s^{+}{\pi }^{-}$ decays by the LHCb experiment.

We investigate the exclusive rare semileptonic decays $B_c\to D_s^{(*)}(\ell \ell ,\nu \overline{\nu })$ induced by neutral current transition $b\to s(\ell \ell ,\nu \overline{\nu })$ in the presence of nonuniversal $Z^{\prime }$, scalar and vector leptoquark new physics models. We constrain the new physics parameter space by using the latest experimental measurements of $R_{K^{(*)}}$, $P_5^{\prime }$, $\mathcal{B}(B_s\to \varphi {\mu }^{+}{\mu }^{-})$ and $\mathcal{B}(B_s\to {\mu }^{+}{\mu }^{-})$. Throughout the analysis, we choose to work with the particular new physics scenario $C_9^{\mu \mu }(NP)=-C_{10}^{\mu \mu }(NP)$ where both $Z^{\prime }$, $S_{1/3}^3$, and $U_{-2/3}^3$ leptoquarks satisfy the condition. Using these new coupling parameters, we scrutinize the several physical observables such as differential branching fraction, the forward backward asymmetry, the lepton polarization asymmetry, the angular observable $P_5^{\prime }$, and the lepton flavor universal sensitive observables, including the ratio of branching ratio $R_{D_s^{(*)}}$ and the few $Q$ parameters in the $B_c\to D_s^{(*)}{\mu }^{+}{\mu }^{-}$ and $B_c\to D_s^{(*)}\nu \overline{\nu }$ decay processes.

In the context of the minimal left-right symmetric model, we study the interplay between current and future neutrinoless double beta ($0\nu \beta \beta$) decay experiments, long-lived particle searches at the LHC main detectors ATLAS/CMS, and the proposed far detector MATHUSLA. The heavy Majorana neutrino can be produced in association with an electron from the decay of $W$ boson for a nonzero left-right mixing and subsequently decays into another electron with the same charge and jets. Owing to the suppression of large right-handed charged gauge boson $W_R$ mass, the heavy neutrinos could be long-lived. We show that long-lived particle (LLP) searches for heavy Majorana neutrinos in the same-sign dilepton channel at the LHC can be used to extend $W_R$ boson mass reach relative to the reach of the Keung-Senjanovic (KS) process. Finally, we show that sensitivities of LLP searches at the high-luminosity LHC with main detectors ATLAS/CMS are competitive with those of future $0\nu \beta \beta$ decay searches.

We present a new Monte Carlo event generator for the hadronic production of four top quarks in the powheg box framework. Besides the dominant next-to-leading order QCD corrections at $\mathcal{O}({\alpha }_s^5)$ we also include all subleading electroweak productions channels at leading-order accuracy. We validate our theoretical predictions by comparing to parton-shower matched predictions obtained within the mc@nlo framework for stable top quarks. Furthermore, we investigate in detail the various sources of theoretical uncertainties. Finally, we investigate a single lepton plus jets signature to study for the first time the impact of the electroweak production modes as well as spin-correlation effects at the fiducial level.

We study the cross sections for the electroproduction of the $P_c(4312)$ particle, a recently discovered pentaquark state, in electron-proton collisions assuming possible quantum numbers to be $J^P={\frac{1}{2}}^{\pm },{\frac{3}{2}}^{\pm }$. $\sqrt{s}$ is set to the energy of the future Electron Ion Collider at Brookhaven National Laboratory, in order to asses the possibility of the measurement in this facility. One can discriminate the spin of $P_c(4312)$ by comparing the pseudorapidity distribution in two different polarization configurations for proton and electron beams. Furthermore, the parity of $P_c(4312)$ can be discerned by analyzing the decay angle in the $P_c\to p+J/\psi$ channel. While the overall magnitudes of the cross sections depend sensitively on the form factor used, the dependencies cancel out in the ratios and beam asymmetry. For its capability to simultaneously polarize proton and electron beams, the Electron Ion Collider can be considered as the future facility for precision measurements of heavy pentaquarks.

We revisit the holographic description of strange baryons in the context of the Sakai-Sugimoto construction, by considering the strange quark mass as heavy. Hyperons are described by a massive $(K,K^{*})$ multiplet, bound to a light-flavor instanton in bulk, much in the spirit of the Callan-Klebanov construction. The modular Hamiltonian maps onto the Landau problem, a charged particle in a two-dimensional external magnetic field, induced by the bulk Chern-Simons interaction, plus spin-orbit coupling. The ensuing holographic hyperon spectrum compares fairly with the empirical one. The holographic strange pentaquark baryon ${\mathrm{\Theta }}_s^{+}$ is shown to be unbound.

We show that an all-optical configuration of the laser-electron collision in the ${\lambda }^3$ configuration based on 10 PW-class lasers presents a viable platform for reaching the range of parameters where a perturbative QED in strong external electromagnetic field breaks. This case is contingently referred to as a case of the nonperturbative QED, and this range of parameters is the intriguing goal from an experimental point of view because of a possible manifestation of a new physics of the interaction of a highly radiating particle with a strong electromagnetic field. We show that the strong-field region can be reached by electrons having initial energy higher than 50 GeV. Our theoretical considerations are in agreement with three-dimensional particle-in-cell simulations. While increasing of the electron energy raises the number of electrons experiencing the strong-field region, the observable signature of photon emission radiative correction in the strong field is expected to fade out when the electron energy surpasses the optimal value. This threshold of electron energy is identified and the parameters for achieving the nonperturbative limit of QED are provided.