We extend our analysis of the implications of hadronic supersymmetry for heavy-light hadrons in light-front holographic QCD. Although conformal symmetry is strongly broken by the heavy quark mass, supersymmetry and the holographic embedding of semiclassical light-front dynamics derived from five-dimensional anti-de Sitter space nevertheless determine the form of the confining potential in the light-front Hamiltonian to be harmonic. The resulting light-front bound-state equations lead to a heavy-light Regge-like spectrum for both mesons and baryons. The confinement hadron mass scale and their Regge slopes depend, however, on the mass of the heavy quark in the meson or baryon as expected from heavy quark effective theory. This procedure reproduces the observed spectra of heavy-light hadrons with good precision and makes predictions for yet unobserved states.

We have studied the production and decay of the $f_1(1285)$ into $\pi a_0(980)$ and $K^{*}\overline{K}$ as a function of the mass of the resonance and find a shoulder around 1400 MeV, tied to a triangle singularity, for the $\pi a_0(980)$ mode, and a peak around 1420 MeV with about 60 MeV width for the $K^{*}\overline{K}$ mode. Both of these features agree with the experimental information on which the $f_1(1420)$ resonance is based. In addition, we find that if the $f_1(1420)$ is a genuine resonance, coupling mostly to $K^{*}\overline{K}$ as seen experimentally, one finds unavoidably about a 20% fraction for $\pi a_0(980)$ decay of this resonance, in drastic contradiction with all experiments. Altogether, we conclude that the $f_1(1420)$ is not a genuine resonance, but the manifestation of the $\pi a_0(980)$ and $K^{*}\overline{K}$ decay modes of the $f_1(1285)$ at higher energies than the nominal one.

The reaction $\gamma N\to \eta N$ is studied in the high-energy regime (with photon lab energies $E_{\gamma }^{\mathrm{lab}}>4\mathrm{GeV}$) using information from the resonance region through the use of finite-energy sum rules. We illustrate how analyticity allows one to map the $t$ dependence of the unknown Regge residue functions. We provide predictions for the energy dependence of the beam asymmetry at high energies.

As an update to our previous calculation for spin $J\le 2$, we present the angular moments for exclusive $\overline{B}\to X_J{\ell }_1{\ell }_2$, where ${\ell }_1$ is a charged massless lepton, ${\ell }_2$ is a charged or neutral massless lepton, and $X_J$ is a mesonic system with spin $J\le 4$. The expected applications include higher resonances in the [$K\pi$] system in ${\overline{B}}^0\to K^{-}{\pi }^{+}{\mu }^{-}{\mu }^{+}$ at LHCb in Run II, and in the [$\pi \pi$] system for $\overline{B}\to \pi \pi {\ell }^{-}{\overline{\nu }}_{\ell }$ at Belle II. For the $J\le 2$ case, we also provide a set of consistency relations among the measured moments observables and validate them against the latest measurements from LHCb.

Assuming that neutrinos are Majorana particles, we explore what information can be inferred from future strong limits (i.e. nonobservation) for neutrinoless double beta decay. Specifically we consider the case where the mass hierarchy is normal and the different contributions to the effective mass $⟨m{⟩}_{ee}$ partly cancel. We discuss how this fixes the two Majorana $CP$ phases simultaneously from the Majorana triangle and how it limits the lightest neutrino mass $m_1$ within a narrow window. The two Majorana $CP$ phases are in this case even better determined than in the usual case for larger $⟨m{⟩}_{ee}$. We show that the uncertainty in these predictions can be significantly reduced by the complementary measurement of reactor neutrino experiments, especially the medium baseline version JUNO/RENO-50. We also estimate the necessary precision on $⟨m{⟩}_{ee}$ to infer nontrivial Majorana $CP$ phases and the upper limit $⟨m{⟩}_{ee}\lesssim 1\mathrm{meV}$ sets a target for the design of future neutrinoless double beta decay experiments.

Nonperturbative renormalization group techniques have recently proven a powerful tool to tackle the nontrivial infrared dynamics of light scalar fields in de Sitter space. In the present article, we develop the formalism beyond the local potential approximation employed in earlier works. In particular, we consider the derivative expansion, a systematic expansion in powers of field derivatives, appropriate for long wavelength modes, that we generalize to the relevant case of a curved metric with Lorentzian signature. The method is illustrated with a detailed discussion of the so-called local potential approximation prime which, on top of the full effective potential, includes a running (but field-independent) field renormalization. We explicitly compute the associated anomalous dimension for $\mathrm{O}(N)$ theories. We find that it can take large values along the flow, leading to sizable differences as compared to the local potential approximation. However, it does not prevent the phenomenon of gravitationally induced dimensional reduction pointed out in previous studies. We show that, as a consequence, the effective potential at the end of the flow is unchanged as compared to the local potential approximation, the main effect of the running anomalous dimension being merely to slow down the flow. We discuss some consequences of these findings.

We examine a holographic model in which a $U(1)$ symmetry and translational invariance are broken spontaneously at the same time. Our construction provides an example of a system with pair-density wave order, in which the superconducting order parameter is spatially modulated but has a zero average. In addition, the charge density oscillates at twice the frequency of the scalar condensate. Depending on the choice of parameters, the model also admits a state with coexisting superconducting and charge-density wave orders, in which the scalar condensate has a uniform component.

Beam dump experiments have been used to search for new particles with null results interpreted in terms of limits on masses $m_{\varphi }$ and coupling constants $\epsilon$. However these limits have been obtained by using approximations [including the Weizsäcker-Williams (WW) approximation] or Monte-Carlo simulations. We display methods, using a new scalar boson as an example, to obtain the cross section and the resulting particle production numbers without using approximations or Monte-Carlo simulations. We show that the approximations cannot be used to obtain accurate values of cross sections. The corresponding exclusion plots differ by substantial amounts when seen on a linear scale. In the event of a discovery, we generate pseudodata (assuming given values of $m_{\varphi }$ and $\epsilon$) in the currently allowed regions of parameter space. The use of approximations to analyze the pseudodata for the future experiments is shown to lead to considerable errors in determining the parameters. Furthermore, a new region of parameter space can be explored without using one of the common approximations, $m_{\varphi }\gg m_e$. Our method can be used as a consistency check for Monte-Carlo simulations.

We explore the effects of photon induced (PI) production of a dilepton final state in the Large Hadron Collider environment. Using QED parton distribution function (PDF) sets we can treat the photons as real partons inside the protons and compare their yield directly to that of the Drell-Yan (DY) process. In particular, we concentrate on an error analysis of the two mechanisms. In order to do so, we use the neural network parton distribution functions (NNPDF) set, which comes with a set of replicas to estimate the systematic PDF error, and the CT14 set. On the one hand, we find that the PI contribution becomes dominant over DY above a dilepton invariant mass of 3 TeV. On the other hand, the PI predictions are affected by a large uncertainty coming from the QED PDFs, well above the one affecting the DY mode. We assess the impact of these uncertainties in the context of resonant and nonresonant searches for a neutral massive vector boson ($Z^{\prime }$) through the differential cross section and forward-backward asymmetry (AFB) observables as a function of the dilepton invariant mass. While the former is subject to the aforementioned significant residual errors the latter shows the systematic error cancellation expected (recall that AFB is a ratio of cross sections) even in presence of PI contributions, so that the recently emphasized key role played by AFB as a valid tool for both $Z^{\prime }$ discovery and interpretation in both resonant and nonresonant mode is further consolidated.

We study the behavior of strongly interacting matter under an external constant magnetic field in the context of nonlocal chiral quark models within the mean field approximation. We find that at zero temperature the behavior of the quark condensates shows the expected magnetic catalysis effect, our predictions being in good quantitative agreement with lattice QCD results. On the other hand, in contrast to what happens in the standard local Nambu-Jona-Lasinio model, when the analysis is extended to the case of finite temperature, our results show that nonlocal models naturally lead to the inverse magnetic catalysis effect.

Leptonic unitarity triangles (LUT) provide fundamental means to geometrically describe $CP$ violation in neutrino oscillation. In this work, we use LUT to present a new geometrical interpretation of the vacuum oscillation probability and derive a compact new oscillation formula in terms of only three independent parameters of the corresponding LUT. Then, we systematically study matter effects in the geometrical formulation of neutrino oscillation with $CP$ violation. Including nontrivial matter effects, we derive a very compact new oscillation formula by using the LUT formulation. We further demonstrate that this geometrical formula holds well for applications to neutrino oscillations in matter, including the long baseline experiments T2K, MINOS, $\mathrm{NO}\nu A$, and DUNE.

Certain models with rank-3 tensor degrees of freedom have been shown by Gurau and collaborators to possess a novel large $N$ limit, where $g^2{N}^3$ is held fixed. In this limit the perturbative expansion in the quartic coupling constant, $g$, is dominated by a special class of “melon” diagrams. We study “uncolored” models of this type, which contain a single copy of real rank-3 tensor. Its three indices are distinguishable; therefore, the models possess $O(N{)}^3$ symmetry with the tensor field transforming in the tri-fundamental representation. Such uncolored models also possess the large $N$ limit dominated by the melon diagrams. The quantum mechanics of a real anticommuting tensor therefore has a similar large $N$ limit to the model recently introduced by Witten as an implementation of the Sachdev-Ye-Kitaev (SYK) model which does not require disorder. Gauging the $O(N{)}^3$ symmetry in our quantum mechanical model removes the nonsinglet states; therefore, one can search for its well-defined gravity dual. We point out, however, that the model possesses a vast number of gauge-invariant operators involving higher powers of the tensor field, suggesting that the complete gravity dual will be intricate. We also discuss the quantum mechanics of a complex 3-index anticommuting tensor, which has $U(N{)}^2\times O(N)$ symmetry and argue that it is equivalent in the large $N$ limit to a version of SYK model with complex fermions. Finally, we discuss similar models of a commuting tensor in dimension $d$. While the quartic interaction is not positive definite, we construct the large $N$ Schwinger-Dyson equation for the two-point function and show that its solution is consistent with conformal invariance. We carry out a perturbative check of this result using the $4-\epsilon$ expansion.

We introduce the notion of fluid approximation of a quantum spherical black hole in the context of loop quantum gravity. In this limit, the microstates of the black hole are intertwiners between “large” representations $s_i$ that typically scale as $s_i\sim \sqrt{a_H}$ where $a_H$ denotes the area of the horizon in Planck units. The punctures with large colors are, for the black hole horizon, similar to what the fluid parcels are for a classical fluid. We dub them puncels. Hence, in the fluid limit, the horizon is composed by puncels that are themselves interpreted as composed (in the sense of the tensor product) by a large number of more fundamental intertwiners. We study the spectrum of the Euclidean volume acting on puncels and we compute its quantum fluctuations. Then, we propose an interpretation of black hole radiation based on the properties of the quantum fluctuations of the Euclidean volume operator. We estimate a typical temperature of the black hole and we show that it scales as the Hawking temperature.

In the present paper, we provide a scheme to probe the gradient of gravity at the nanoscale in a levitated nanomechanical resonator coupled to a cavity via two-field optical control. The enhanced sharp peak on the probe spectrum will suffer a distinct shift with the nonuniform force being taken into consideration. The nonlinear optics with very narrow bandwidth $({10}^{-8}\mathrm{Hz})$ resulting from the extremely high-quality factor will lead to a superresolution of ${10}^{-20}\mathrm{N}/\mathrm{m}$ for the measurement of gravity gradient. The improved sensitivity may offer new opportunities for detecting Yukawa moduli forces and Kaluza-Klein gravitons in extra dimensions.

In a recent paper, one of us studied spherically symmetric, asymptotically flat solutions of shape dynamics, finding that the spatial metric has characteristics of a wormhole—two asymptotically flat ends and a minimal-area sphere, or “throat,” in between. In this paper, we investigate whether that solution can emerge as a result of gravitational collapse of matter. With this goal, we study the simplest kind of spherically symmetric matter: an infinitely-thin shell of dust. Our system can be understood as a model of a star accreting a thin layer of matter. We solve the dynamics of the shell exactly and find that, indeed, as it collapses, the shell leaves in its wake the wormhole metric. In the maximal-slicing time we use for asymptotically flat solutions, the shell only approaches the throat asymptotically and does not cross it in a finite amount of time (as measured by a clock “at infinity”). This leaves open the possibility that a more realistic cosmological solution of shape dynamics might see this crossing happening in a finite amount of time (as measured by the change of relational or shape degrees of freedom).

In quantum theory it is possible to explain time, and dynamics, in terms of entanglement. This is the timeless approach to time, which assumes that the universe is in a stationary state, where two noninteracting subsystems, the “clock” and the “rest,” are entangled. As a consequence, by choosing a suitable observable of the clock, the relative state of the rest of the universe evolves unitarily with respect to the variable labeling the clock observable’s eigenstates, which is then interpreted as time. This model for an “evolution without evolution” (Page and Wootters, 1983), albeit elegant, has never been developed further, because it was criticized for generating severe ambiguities in the dynamics of the rest of the universe. In this paper we show that there are no such ambiguities; we also update the model, making it amenable to possible new applications.

We examine the cosmological sector of a gauge theory of gravity based on the SO(4,2) conformal group of Minkowski space. We allow for conventional matter coupled to the spacetime metric as well as matter coupled to the field that gauges special conformal transformations. An effective vacuum energy appears as an integration constant, and this allows us to recover the late time acceleration of the Universe. Furthermore, gravitational fields sourced by ordinary cosmological matter (i.e. dust and radiation) are significantly weakened in the very early Universe, which has the effect of replacing the big bang with a big bounce. Finally, we find that this bounce is followed by a period of nearly exponential slow roll inflation that can last long enough to explain the large scale homogeneity of the cosmic microwave background.

In many models in condensed matter and high-energy physics, one finds inhomogeneous phases at high density and low temperature. These phases are characterized by a spatially dependent condensate or order parameter. A proper calculation requires that one takes the vacuum fluctuations of the model into account. These fluctuations are ultraviolet divergent and must be regularized. We discuss different ways of consistently regularizing and renormalizing quantum fluctuations, focusing on momentum cutoff, symmetric energy cutoff, and dimensional regularization. We apply these techniques calculating the vacuum energy in the Nambu-Jona-Lasinio model in $1+1$ dimensions in the large-$N_c$ limit and in the $3+1$ dimensional quark-meson model in the mean-field approximation both for a one-dimensional chiral-density wave.

We present the next-to-leading-order (NLO) corrections to the fragmentation process of a heavy quark to a ${{}^{3}S}_1$ wave heavy quarkonium. The virtual and real corrections are calculated by using the dimensional regularization method. The divergences due to virtual NLO corrections are analytically extracted then we explain how the poles from phase-space integrals and from loop integrals are canceled by renormalization. We use the eikonal scheme to evaluate the soft real corrections in $4-2ϵ$ dimensions. Our numerical calculations show the fragmentation function (FF) at NLO is dependent on both the $\mu$ scale and the initial quark energy. These corrections have a significant effect on the shape and probability of the FF.

The question of whether there exist bound states of two heavy quarks $Q=(c,b)$ and antiquarks $\overline{Q}=(\overline{c},\overline{b})$, distinct from a pair of quark-antiquark mesons, has been debated for more than forty years. We estimate masses of $Q_1{Q}_2{\overline{Q}}_3{\overline{Q}}_4$ resonant states $X_{Q_1{Q}_2{\overline{Q}}_3{\overline{Q}}_4}$ and suggest a means of producing and observing them. We concentrate on the $cc\overline{c}\overline{c}$ channel which is most easily produced and the $bb\overline{b}\overline{b}$ channel which has a better chance of being relatively narrow. We obtain $M(X_{cc\overline{c}\overline{c}})=\mathrm{6,192}\pm 25\mathrm{MeV}$ and $M(X_{bb\overline{b}\overline{b}})=\mathrm{18,826}\pm 25\mathrm{MeV}$, for the $J^{PC}=0^{++}$ states involving charmed and bottom tetraquarks, respectively. An experimental search for these states in the predicted mass range is highly desirable.