We consider electrically neutral complex-vector particles $V$ below the GeV mass scale that, from a low-energy perspective, couple to the photon via higher-dimensional form factor interactions. We derive ensuing astrophysical constraints by considering the anomalous energy loss from the Sun, Horizontal Branch, and Red Giant stars as well as from SN1987A that arise from vector pair production in these environments. Under the assumption that the dark states $V$ constitute dark matter, the bounds are then complemented by direct and indirect detection as well as cosmological limits. The relic density from freeze-out and freeze-in mechanisms is also computed. On the basis of a UV-complete model that realizes the considered effective couplings, we also discuss the naturalness of the constrained parameter space, and provide an analysis of the zero mass limit of $V$.

We construct a model of the quintessence axion based on a gauged chiral $U(1)$ symmetry and an additional flat fifth dimension. The required high qualities are guaranteed by the brane separation. The observed cosmological constant (i.e., the potential energy of the quintessence axion) is determined by the size of the extra dimension and the axion decay constant $F_a$ is fixed almost at $F_a\simeq {10}^{17}\mathrm{GeV}$, which is sufficiently large for the stability of the axion field near the hilltop of its potential. Furthermore, the movement of the axion can also easily explain the recently reported isotropic cosmic birefringence of the cosmic microwave background photon.

We calculate the decay rates for ${\eta }_c\to \gamma \gamma$, $J/\psi \to \gamma {\eta }_c$ and $J/\psi \to {\eta }_c{e}^{+}{e}^{-}$ in lattice QCD with $u$, $d$, $s$ and $c$ quarks in the sea for the first time. We improve significantly on previous theory calculations to achieve accuracies of 1–2%, giving lattice QCD results that are now more accurate than the experimental values. In particular our results transform the theoretical picture for ${\eta }_c\to \gamma \gamma$ decays. We use gluon field configurations generated by the MILC collaboration that include $n_f=2+1+1$ flavors of highly improved staggered sea quarks at four lattice spacing values from 0.15 fm to 0.06 fm and with sea u/d masses down to their physical value. We also implement the valence $c$ quarks using the highly improved staggered quark action. We find $\mathrm{\Gamma }({\eta }_c\to \gamma \gamma )=6.788(45{)}_{\mathrm{fit}}(41{)}_{\mathrm{syst}}\mathrm{keV}$, in good agreement with experimental results using $\gamma \gamma \to {\eta }_c\to K\overline{K}\pi$ but in $4\sigma$ tension with the Particle Data Group global fit result [R. L. Workman (Particle Data Group), Prog. Theor. Exp. Phys. 2022, 083C01 (2022)]; we suggest this fit is revisited. We also calculate $\mathrm{\Gamma }(J/\psi \to \gamma {\eta }_c)=2.219(17{)}_{\mathrm{fit}}(18{)}_{\mathrm{syst}}(24{)}_{\mathrm{expt}}(4{)}_{\mathrm{QED}}\mathrm{keV}$, in good agreement with results from CLEO, and predict the Dalitz decay rate $\mathrm{\Gamma }(J/\psi \to {\eta }_c{e}^{+}{e}^{-})=0.01349(15{)}_{\mathrm{latt}}(15{)}_{\mathrm{expt}}(13{)}_{\mathrm{QED}}\mathrm{keV}$. We use our results to calibrate other theoretical approaches and to test simple relationships between the form factors and $J/\psi$ decay constant expected in the nonrelativistic limit.

Polarizabilities reveal valuable information on the internal structure of hadrons in terms of charge and current distributions. For neutral hadrons, the standard approach is the background field method, but for a charged hadron, its acceleration under the applied field complicates the isolation of the polarization energy. In this work, we explore an alternative method based on four-point functions in lattice QCD. The approach offers a transparent picture on how polarizabilities arise from photon, quark, and gluon interactions. We carry out a proof-of-concept simulation on the electric polarizability of a charged pion, using quenched Wilson action on a ${24}^3\times 48$ lattice at $\beta =6.0$ with pion mass from 1100 MeV to 370 MeV. We show in detail the evaluation and analysis of the four-point correlation functions and report results on charge radius and electric polarizability. Our results from connected diagrams suggest that charged pion ${\alpha }_E$ is due to a cancellation between elastic and inelastic contributions. It would be interesting to see how the cancellation plays out at smaller pion masses in future simulations.

Masses of positive-parity and negative-parity diquarks are investigated at finite temperature with a quark chemical potential. We employ the three-flavor Nambu-Jona-Lasinio model, in order to delineate chiral properties of the diquarks, in particular, the mass degeneracy of chiral partners under extreme conditions. We focus on the effects of $U(1{)}_A$ axial anomaly on manifestation of the chiral-partner structures. We find that, in the absence of anomaly effects to the diquarks, the mass degeneracies in all $[ud]$, $[su]$, and $[sd]$ diquark sectors take place prominently above the pseudocritical temperature of the chiral restoration. On the other hand, the anomaly effects are found to hinder the $[ud]$ diquark from exhibiting the mass degeneracy, accompanied by a slow reduction of the $\overline{s}s$ condensate, while the $[su]$ and $[sd]$ diquarks are not much affected. Our present investigation will provide useful information on the chiral-partner structure with the anomaly effects of diquarks for heavy-ion collision experiments of singly heavy baryons and doubly heavy tetraquarks, and for future lattice simulations of the diquarks.

We extend the discussion of the recently discovered “anomaly poles” in QCD Compton scattering. We perform the complete one-loop calculation of the Compton amplitude using momentum transfer $t$ as the regulator of collinear divergences. In the gluon channel, we confirm the presence of poles $1/t$ in both the real and the imaginary parts of the amplitude. In the quark channel, we find unexpected infrared single $1/\epsilon$ and double $1/{\epsilon }^2$ poles. We then perform the one-loop calculation of the leading-twist quark generalized parton distributions (GPDs) for quark and gluon external states with the same regulators and find that all these singular terms can be systematically absorbed into the GPDs, showing that QCD factorization is restored to this order. Having established this, we discuss the fate of the $1/t$ poles. We argue that they become the nonperturbative building blocks of GPDs that encode the chiral and trace anomalies of QCD, in a way consistent with the known constraints these anomalies impose on the nucleon axial and gravitational form factors. The scope of research on GPDs can therefore be expanded to address the manifestation and implications of quantum anomalies in high-energy exclusive processes.

Analytic continuation of the perturbative series from spacelike to timelike regions is performed using renormalization group summed perturbation theory (RGSPT). This method provides an all-order summation of kinematic “${\pi }^2$-terms” accessible from a given order of a perturbative series. The impact of the summation of these terms is studied for Higgs boson decay and electromagnetic R-ratio in the perturbative QCD. Results obtained using RGSPT have improved convergence behavior in addition to significantly reduced renormalization scale dependence compared to fixed-order perturbation theory (FOPT). The higher-order behavior using the Padé approximant is also studied for processes considered.

If collapsars are sources for both high-energy (HE) neutrinos and $r$-process nuclei, then the profuse low-energy antineutrinos from the $\beta$ decay of the newly synthesized nuclei can annihilate the HE neutrinos. Considering HE neutrinos produced at internal shocks induced by intermittent mildly magnetized jets, we show that such annihilation suppresses the overall HE neutrino spectrum at $\gtrsim 300\mathrm{TeV}$ and produces a corresponding flavor composition of $(F_{{\nu }_e+{\overline{\nu }}_e}:F_{{\nu }_{\mu }+{\overline{\nu }}_{\mu }}:F_{{\nu }_{\tau }+{\overline{\nu }}_{\tau }}{)}_{\star }\approx (1:10:1)$ at source. We find that the emergent HE neutrino flux can well fit the diffuse flux observed at IceCube if contributions from all similar sources are taken into account. Our results highlight the unique role of HE neutrinos in supporting collapsars as sources for $r$-process nuclei, and can be tested by detection of HE neutrinos from individual sources and accurate measurement of the diffuse HE neutrino flux spectrum and flavor composition.

We consider the target space theory of bosonic and heterotic string theory to first order in ${\alpha }^{\prime }$ compactified to three dimensions, using a formulation that is manifestly $T$ duality invariant under $\mathrm{O}(d,d,\mathbb{R})$ with $d=23$ and $d=7$, respectively. While the two-derivative supergravity exhibits a symmetry enhancement to the $U$ duality group $\mathrm{O}(d+1,d+1)$, the continuous group is known to be broken to $\mathrm{O}(d,d,\mathbb{R})$ by the first ${\alpha }^{\prime }$ correction. We revisit this observation by computing the full effective actions in three dimensions to first order in ${\alpha }^{\prime }$ by dualizing the vector gauge fields. We give a formally $\mathrm{O}(d+1,d+1)$ invariant formulation by invoking a vector compensator, and we observe a chiral pattern that allows one to reconstruct the bosonic action from the heterotic action. Furthermore, we obtain a particular massive deformation by integrating out the external $B$ field. This induces a novel Chern-Simons term based on composite connections that, remarkably, is $\mathrm{O}(d+1,d+1)$ invariant to leading order in the deformation parameter.

We report two surprising results on ${\alpha }^{\prime }$ corrections in string theory restricted to massless fields. First, for critical dimension Bianchi type I cosmologies with $q$ scale factors only $q-1$ of them have nontrivial ${\alpha }^{\prime }$ corrections. In particular, for Friedmann-Robertson-Walker backgrounds all ${\alpha }^{\prime }$ corrections are trivial. Second, in noncritical dimensions, all terms in the spacetime action other than the cosmological term are field redefinition equivalent to terms with arbitrarily many derivatives, with the latter generally of the same order. Assuming an ${\alpha }^{\prime }$ expansion with coefficients that fall off sufficiently fast, we consider field redefinitions consistent with this falloff and classify the higher-derivative terms for two-dimensional string theory with one timelike isometry. This most general duality-invariant theory permits black-hole solutions, and we provide perturbative and nonperturbative tools to explore them.

When implementing a nonlinear constraint in quantum field theory by means of a Lagrange multiplier, $\lambda (x)$, it is often the case that quantum dynamics induce quadratic and even higher-order terms in $\lambda (x)$, which then does not enforce the constraint anymore. This is illustrated in the case of unimodular gravity, where the constraint is that the metric tensor has to be unimodular ($g(x)\equiv \det g_{\mu \nu }(x)=-1$).

In this paper we consider $T\overline{T}$ deformations in the context of $pp$ waves obtained from gravity duals. We propose a deformation of ${\mathrm{AdS}}_5\times S^5$ similar to the deformation of the single trace $T\overline{T}$ deformation of ${\mathrm{AdS}}_3\times S^3\times T^4$ with NS-NS flux, and study it through the Penrose limit, concluding that it must correspond to some dipole theory, probably noncommutative. We $T\overline{T}$ deform the world sheet string for the ${\mathrm{AdS}}_5\times S^{5}pp$ wave, and find a corresponding spin chain Hamiltonian. Finally, directly $T\overline{T}$ deforming the spin chain Hamiltonian obtained from the $pp$ wave, we find that it corresponds to an equivalent Berenstein-Maldacena-Nastase (BMN) sector of the $\mathcal{N}=4$ super Yang-Mills.

Axions mix with neutral pions after the QCD phase transition through their common coupling to the radiation bath via a Chern-Simons term, as a consequence of the $U(1)$ anomaly. The nonequilibrium effective action that describes this mixing phenomenon is obtained to second order in the coupling of neutral pions and axions to photons. We show that a misaligned axion condensate induces a neutral pion condensate after the QCD phase transition. We argue that even a very small axion-photon coupling will “seed” the chiral phase transition. The dynamics of the pion condensate displays long and short timescales and decays on the longer timescale exhibiting a phenomenon akin to the “purification” in a kaon beam. On the intermediate timescales the macroscopic pion condensate is proportional to a condensate of the Abelian Chern-Simons term induced by the axion. We argue that the coupling to the common bath also induces kinetic mixing. We obtain the axion and pion populations, and these exhibit thermalization with the bath. The mutual coupling to the bath induces long-lived axion–neutral pion coherence independent of initial conditions. The framework of the effective action and many of the consequences are more broadly general and applicable to scalar or pseudoscalar particles mixing in a medium.

In the model of quantum gravity proposed in [J. High Energy Phys. 06 (2020) 70], dynamical spacetime arises as a collective phenomenon of underlying quantum matter. Without a preferred decomposition of the Hilbert space, the signature, topology and geometry of an emergent spacetime depend upon how the total Hilbert space is partitioned into local Hilbert spaces. In this paper, it is shown that the massless graviton emerges in the spacetime realized from a Hilbert space decomposition that supports a collection of largely unentangled local clocks.

The dynamics of the torsion-powered teleparallel theory are only viable because 36 multiplier fields disable all components of the Riemann-Cartan curvature. We generalize this suggestive approach by considering Poincaré gauge theory in which 60 such “geometric multipliers” can be invoked to disable any given irreducible part of the curvature, or indeed the torsion. Torsion theories motivated by a weak-field analysis frequently suffer from unwanted dynamics in the strong-field regime, such as the activation of ghosts. By considering the propagation of massive, parity-even vector torsion, we explore how geometric multipliers may be able to limit strong-field departures from the weak-field Hamiltonian constraint structure and consider their tree-level phenomena.

Theories beyond general relativity (GR) modify the propagation of gravitational waves (GWs). In some, inhomogeneities (aka, gravitational lenses) allow interactions between the metric and additional fields to cause lens-induced birefringence (LIB): a different speed of the two linear GW polarizations ($+$ and $\times$). Inhomogeneities then act as nonisotropic crystals, splitting the GW signal into two components whose relative time delay depends on the theory and lens parameters. Here we study the observational prospects for GW scrambling, i.e. when the time delay between both GW polarizations is smaller than the signal’s duration and the waveform recorded by a detector is distorted. We analyze the latest LIGO-Virgo-KAGRA catalog, GWTC-3, and find no conclusive evidence for LIB. The highest log Bayes factor that we find in favor of LIB is 3.21 for GW190521, a particularly loud but short event. However, when accounting for false alarms due to (Gaussian) noise fluctuations, this evidence is below $1\sigma$. The tightest constraint on the time delay is $<0.51\mathrm{ms}$ at 90% confidence level (CL) from GW200311_115853. From the nonobservation of GW scrambling, we constrain the optical depth for LIB, accounting for the chance of randomly distributed lenses (e.g. galaxies) along the line of sight. Our LIB constraints on a (quartic) scalar-tensor Horndeski theory are more stringent than Solar System tests for a wide parameter range and comparable to GW170817 in some limits. Interpreting GW190521 as an active galactic nucleus (AGN) binary (i.e. taking an AGN flare as a counterpart) allows even more stringent constraints. Our results demonstrate the potential and high sensitivity achievable by tests of GR, based on GW lensing.

Perturbations to the cosmic baryon density—and thus to the total-matter density—can be induced by magnetohydronamic forces if there are primordial magnetic fields. The power spectrum for these density perturbations was first provided in 1996, but without much in the way of detail in the derivation, and there has been confusion in the intervening years about this calculation. In this brief note, we rederive this power spectrum using modern conventions, provide a simplified result, and identify some of the discrepancies in the literature.

Models of dark sectors with a mass threshold can have important cosmological signatures. If, in the era prior to recombination, a relativistic species becomes nonrelativistic and is then depopulated in equilibrium, there can be measurable impacts on the cosmic microwave background as the entropy is transferred to lighter relativistic particles. In particular, if this “step” occurs near $z\sim 20$, 000, the model can naturally accommodate larger values of $H_0$. If this stepped radiation is additionally coupled to dark matter, there can be a meaningful impact on the matter power spectrum as dark matter can be coupled via a species that becomes nonrelativistic and depleted. This can naturally lead to suppressed power at scales inside the sound horizon before the step, while leaving conventional cold dark matter signatures for power outside the sound horizon. We study these effects and show such models can naturally provide lower values of $S_8$ than scenarios without a step. This suggests these models may provide an interesting framework to address the $S_8$ tension, both in concert with the $H_0$ tension and without.

New-generation direct searches for low mass dark matter feature detection thresholds at energies well below 100 eV, much lower than the energies of commonly used x-ray calibration sources. This requires new calibration sources with sub-keV energies. When searching for nuclear recoil signals, the calibration source should ideally cause monoenergetic nuclear recoils in the relevant energy range. Recently, a new calibration method based on the radiative neutron capture on ${}^{182}\mathrm{W}$ with subsequent deexcitation via single $\gamma$-emission leading to a nuclear recoil peak at 112 eV was proposed. The CRESST-III dark matter search operated several ${\mathrm{CaWO}}_4$-based detector modules with detection thresholds below 100 eV in the past years. We report the observation of a peak around the expected energy of 112 eV in the data of three different detector modules recorded while irradiated with neutrons from different AmBe calibration sources. We compare the properties of the observed peaks with geant-4 simulations and assess the prospects of using this for the energy calibration of CRESST-III detectors.

The mass formulas and decay constants of electrically charged and strange pseudoscalar mesons are analyzed within the combined framework of the Nambu–Jona-Lasinio model and the $1/N_c$ expansion up to $\mathcal{O}(1/N_c^2)$. The light quark masses explicitly violating $SU(3{)}_L\times SU(3{)}_R$ chiral symmetry of the strong interactions are taken to be of order $\mathcal{O}(1/N_c)$. The Fock-Schwinger proper-time method and the Volterra series are used to derive the effective action. A set of sum rules is obtained that relates the phenomenological values of the masses of pseudoscalar mesons to the mass ratios of light quarks. It is shown that combining the new sum rules with the experimental data on the decay width $\eta \to 3\pi$ allows one to establish limits for the ratios: $0.47<m_u/m_d<0.59$ and $18.60<m_s/m_d<19.66$. A comparison with the results of similar calculations in $1/N_c$ chiral perturbation theory is made.