We study the changes in the short-distance quark structure of the Nambu-Goldstone boson when the long-distance symmetry-breaking scales are depleted controllably. We achieve this by studying the valence parton distribution function (PDF) of pion in $2+1$ dimensional two-color QCD, with the number $N$ of massless quarks as the tunable parameter that slides the theory from being strongly broken for $N=0$ to the conformal window for $N>4$, where the theory is gapped by the fixed finite volume. We perform our study nonperturbatively using lattice simulations with $N=0$, 2, 4, 8 flavors of nearly massless two-component Wilson-Dirac sea quarks and employ the leading-twist formalism (LaMET/SDF) to compute the PDF of pion at a fixed valence mass. We find that the relative variations in the first few PDF moments are only mild compared to the changes in decay constant, but the shape of the reconstructed $x$-dependent PDF itself dramatically changes from being broad in the scale-broken sector to being sharply peaked in the near-conformal region, best reflected in PDF shape observables such as the cumulants.

The axial charge of the triton is investigated using lattice quantum chromodynamics (QCD). Extending previous work at heavier quark masses, calculations are performed using three ensembles of gauge field configurations generated with quark masses corresponding to a pion mass of 450 MeV and a single value of the lattice spacing. Finite-volume energy levels for the triton, as well as for the deuteron and diproton systems, are extracted from analysis of correlation functions computed on these ensembles, and the corresponding energies are extrapolated to infinite volume using finite-volume pionless effective field theory (FVEFT). It is found with high likelihood that there is a compact bound state with the quantum numbers of the triton at these quark masses. The axial current matrix elements are computed using background field techniques on one of the ensembles and FVEFT is again used to determine the axial charge of the proton and triton. A simple quark mass extrapolation of these results and earlier calculations at heavier quark masses leads to a value of the ratio of the triton to proton axial charges at the physical quark masses of $g_A^{{}^3\mathrm{H}}/g_A^p={0.91}_{-0.09}^{+0.07}$. This result is consistent with the ratio determined from experiment and prefers values less than unity (in which case the triton axial charge would be unmodified from that of the proton), thereby demonstrating that QCD can explain the modification of the axial charge of the triton.

By an unquenched quark model, we predict a charmed-strange baryon state, namely, the ${\mathrm{\Omega }}_{c0}^d(1P,1/2^{-})$. Its mass is predicted to be 2945 MeV, which is below the ${\mathrm{\Xi }}_c\overline{K}$ threshold due to the nontrivial coupled-channel effect. So the ${\mathrm{\Omega }}_{c0}^d(1P,1/2^{-})$ state could be regarded as the analog of the charmed-strange meson $D_{s0}^{*}(2317)$. It is a good opportunity for the running Belle II experiment to search for this state in the ${\mathrm{\Omega }}_c^{(*)}\gamma$ mass spectrum experiment in the future.

We explore the feasibility of the measurement of charm-jet cross sections in charged-current deep-inelastic scattering at the future Electron-Ion Collider. This channel provides clean sensitivity to the strangeness content of the nucleon in the high-$x$ region. We estimate charm-jet tagging performance with parametrized detector simulations. We show the expected sensitivity to various scenarios for strange parton distribution functions. We argue that this measurement will be key to future QCD global analyses, so it should inform EIC detector designs and luminosity requirements.

We present a study of fits to exclusive $B^0\to D^{*-}{\ell }^{+}{\nu }_{\ell }$ measurements for the determination of the Cabibbo-Kobayashi-Maskawa matrix element magnitude $|V_{cb}|$, based on the most recent Belle untagged measurement. Results are obtained with the Caprini-Lellouch-Neubert (CLN) and Boyd-Grinstein-Lebed (BGL) form factor parametrizations, with and without the inclusion of preliminary lattice QCD (LQCD) measurements of form factors at nonzero hadronic recoil from the JLQCD Collaboration. The CLN and BGL fits are also studied in different scenarios with reduced theoretical assumptions and at higher-order expansions, respectively. To avoid bias from high systematic error correlations, we employ a novel technique in the field of $B$-physics phenomenology with a toy Monte Carlo method using a Cholesky decomposition of the covariance matrix. Using additional input from lattice QCD calculations of form factors at nonzero recoil, in collaboration with JLQCD, allows for well-defined fit results with reduced model dependence in CLN and BGL. The results obtained are consistent between different configurations, ultimately providing a method for a more model-independent exclusive measurement of $|V_{cb}|$. Using preliminary LQCD inputs and assuming a value of $\mathcal{F}(1)=0.904\pm 0.012$, we find $|V_{cb}|=(38.48\pm 0.32\pm 0.97\pm 0.46)\times {10}^{-3}$ in BGL(2,2,2) and $(38.42\pm 0.35\pm 1.05\pm 0.46)\times {10}^{-3}$ in CLNnoHQS, where the errors are statistical, systematic, and related to $\mathcal{F}(1)$, respectively.

We consider mixed three-point correlation functions of the supercurrent and flavor current in three-dimensional $1\le \mathcal{N}\le 4$ superconformal field theories. Our method is based on the decomposition of the relevant tensors into irreducible components to guarantee that all possible tensor structures are systematically taken into account. We show that only parity-even structures appear in the correlation functions. In addition to the previous results obtained in [E. I. Buchbinder et al.J. High Energy Phys. 06 (2015) 138], it follows that supersymmetry forbids parity-odd structures in three-point functions involving the supercurrent and flavor current multiplets.

The linearized Einstein field equations provide a low-energy wave equation for the propagation of gravitational fields which may originate from a high-energy source. Motivated by loop quantum gravity, we propose the polymer quantization scheme to derive the effective propagation of such waves on a classical Friedmann-Lemaître-Robertson-Walker spacetime. To overcome the challenge of polymer quantizing a time-dependent Hamiltonian, we rewrite such a Hamiltonian in a time-independent manner in the extended phase space, polymerize it, and then transform it back to the usual phase space. In this way, we obtain a time-dependent polymer Hamiltonian for the gravitational waves. We then derive the effective equations of motion and show that (i) the form of the waves is modified, (ii) the speed of the waves depends on their frequencies, and (iii) quantum effects become more apparent as waves traverse longer distances.

We develop a number of novel “black-bounce” spacetimes. These are specific regular black holes where the area radius always remains nonzero, thereby leading to a “throat” that is either timelike (corresponding to a traversable wormhole), spacelike (corresponding to a “bounce” into a future universe), or null (corresponding to a “one-way wormhole”). We first perform a general analysis of the regularity conditions for such a spacetime and then consider a number of specific examples. The examples are constructed using a mass function similar to that of Fan-Wang and fall into several particular cases, such as the original Simpson-Visser model, a Bardeen-type model, and other generalizations thereof. We analyze the regularity, energy conditions, and causal structure of these models. The main results are several new geometries, more complex than before, with two or more horizons, with the possibility of an extremal case. We derive a general theorem regarding static spacetime regularity and another general theorem regarding (non)satisfaction of the classical energy conditions.

We propose that the dynamics of a scalar $\varphi$ of mass $\mathcal{O}(10)\mathrm{MeV}$ that is weakly coupled to the Higgs can lead to a first-order electroweak phase transition, fulfilling a key requirement for baryogenesis. The stability of the model near the weak scale requires a suppressed—possibly vanishing—top Yukawa coupling to the Higgs before the transition which rises to the Standard Model value afterwards. This can be accomplished through the dynamics of $\varphi$ via a dimension-five operator. We conjecture that the entire Standard Model flavor structure could turn on, mutatis mutandis, after the electroweak phase transition, via dimension-five interactions of $\varphi$ suppressed by scales ranging from $\mathcal{O}(10^3)\mathrm{TeV}$ to near the Planck mass. Due to its suppressed couplings, $\varphi$ is long lived and can lead to missing energy signals in rare kaon decays, which can be probed by the KOTO experiment.

We present the cosmological implications from final measurements of clustering using galaxies, quasars, and $\mathrm{Ly}\alpha$ forests from the completed Sloan Digital Sky Survey (SDSS) lineage of experiments in large-scale structure. These experiments, composed of data from SDSS, SDSS-II, BOSS, and eBOSS, offer independent measurements of baryon acoustic oscillation (BAO) measurements of angular-diameter distances and Hubble distances relative to the sound horizon, $r_d$, from eight different samples and six measurements of the growth rate parameter, $f{\sigma }_8$, from redshift-space distortions (RSD). This composite sample is the most constraining of its kind and allows us to perform a comprehensive assessment of the cosmological model after two decades of dedicated spectroscopic observation. We show that the BAO data alone are able to rule out dark-energy-free models at more than eight standard deviations in an extension to the flat, $\mathrm{\Lambda }\mathrm{CDM}$ model that allows for curvature. When combined with Planck Cosmic Microwave Background (CMB) measurements of temperature and polarization, under the same model, the BAO data provide nearly an order of magnitude improvement on curvature constraints relative to primary CMB constraints alone. Independent of distance measurements, the SDSS RSD data complement weak lensing measurements from the Dark Energy Survey (DES) in demonstrating a preference for a flat $\mathrm{\Lambda }\mathrm{CDM}$ cosmological model when combined with Planck measurements. The combined BAO and RSD measurements indicate ${\sigma }_8=0.85\pm 0.03$, implying a growth rate that is consistent with predictions from Planck temperature and polarization data and with General Relativity. When combining the results of SDSS BAO and RSD, Planck, Pantheon Type Ia supernovae (SNe Ia), and DES weak lensing and clustering measurements, all multiple-parameter extensions remain consistent with a $\mathrm{\Lambda }\mathrm{CDM}$ model. Regardless of cosmological model, the precision on each of the three parameters, ${\mathrm{\Omega }}_{\mathrm{\Lambda }}$, $H_0$, and ${\sigma }_8$, remains at roughly 1%, showing changes of less than 0.6% in the central values between models. In a model that allows for free curvature and a time-evolving equation of state for dark energy, the combined samples produce a constraint ${\mathrm{\Omega }}_k=-0.0022\pm 0.0022$. The dark energy constraints lead to $w_0=-0.909\pm 0.081$ and $w_a=-0.49_{-0.30}^{+0.35}$, corresponding to an equation of state of $w_p=-1.018\pm 0.032$ at a pivot redshift $z_p=0.29$ and a Dark Energy Task Force Figure of Merit of 94. The inverse distance ladder measurement under this model yields $H_0=68.18\pm 0.79\mathrm{km}{\mathrm{s}}^{-1}{\mathrm{Mpc}}^{-1}$, remaining in tension with several direct determination methods; the BAO data allow Hubble constant estimates that are robust against the assumption of the cosmological model. In addition, the BAO data allow estimates of $H_0$ that are independent of the CMB data, with similar central values and precision under a $\mathrm{\Lambda }\mathrm{CDM}$ model. Our most constraining combination of data gives the upper limit on the sum of neutrino masses at $\sum m_{\nu }<0.115\mathrm{eV}$ (95% confidence). Finally, we consider the improvements in cosmology constraints over the last decade by comparing our results to a sample representative of the period 2000–2010. We compute the relative gain across the five dimensions spanned by $w$, ${\mathrm{\Omega }}_k$, $\sum m_{\nu }$, $H_0$, and ${\sigma }_8$ and find that the SDSS BAO and RSD data reduce the total posterior volume by a factor of 40 relative to the previous generation. Adding again the Planck, DES, and Pantheon SN Ia samples leads to an overall contraction in the five-dimensional posterior volume of 3 orders of magnitude.

We investigate features of the deconfinement phase transition in an $SU(N_c)$ gauge theory as revealed by fluctuations of the order parameter. The tool of choice is an effective model built from one-loop expressions of the field determinants of gluon and ghost, in the presence of a Polyakov loop background field. We show that the curvature masses associated with the Cartan angles, which serve as a proxy to study the $A_0$-gluon screening mass, show a characteristic dip in the vicinity of the transition temperature. The strength of the observables, which reflects a competition between the confining and the deconfining forces, is sensitive to assumptions of dynamics, and thus provides an interesting link between the $Z(N_c)$ vacuum structure and the properties of gluon and ghost propagators.

We investigate the electromagnetic transitions of the singly charmed baryons with spin $3/2$, based on a pion mean-field approach, also known as the chiral quark-soliton model, taking into account the rotational $1/N_c$ corrections and the effects of flavor SU(3) symmetry breaking. We examine the valence- and sea-quark contributions to the electromagnetic transition form factors and find that the quadrupole form factors of the sea-quark contributions dominate over those of the valence-quark ones in the smaller $Q^2$ region, whereas the sea quarks only provide marginal contributions to the magnetic dipole transition form factors of the baryon sextet with spin $3/2$. The effects of the flavor SU(3) symmetry breaking are in general very small except for the forbidden transition ${\mathrm{\Xi }}_c^0\gamma \to {\mathrm{\Xi }}_c^{*0}$ by $U$-spin symmetry. We also discuss the widths of the radiative decays for the baryon sextet with spin $3/2$, comparing the present results with those from other works.

We present a concise derivation of geometric optics in the presence of axionic fields in a curved spacetime. Whenever light can be described via geometric optics (the eikonal approximation), the only difference to the situation without axionic field is the phenomenon of achromatic birefringence. Consequently, redshift of light and distance estimates based on propagating light rays, as well as shear and magnification due to gravitational lensing are not affected by the interaction of light with an axionic field.

Despite the great observational success of the standard cosmological model some discrepancies in the inferred parameter constraints have manifested among a number of cosmological data sets. These include a tension between the expansion rate of our Cosmos as inferred from the cosmic microwave background (CMB) and as found from local measurements, the preference for an enhanced amplitude of CMB lensing, a somewhat low quadrupole moment of the CMB fluctuations as well as a preference for a lower amplitude of matter fluctuations in large-scale structure surveys than inferred from the CMB. We analyze these observational tensions under the addition of spatial curvature and a free CMB background temperature that may deviate from its locally measured value. With inclusion of these parameters, we observe a trend in the parameter constraints from CMB and baryon acoustic oscillation data towards an open and hotter universe with larger current expansion rate, standard CMB lensing amplitudes, lower amplitude of matter fluctuations, and marginally lower CMB quadrupole moment, consistently reducing the individual tensions among the cosmological data sets. Combining this data with local distance measurements, we find a preference for an open and hotter universe beyond the 99.7% confidence level. Finally, we briefly discuss a local void as a possible source for a deviation of the locally measured CMB temperature from its background value and as mimic of spatial curvature for CMB photons. This interpretation implies a $\sim 20\%$ underdensity in our local neighborhood of $\sim 10–100\mathrm{Mpc}$ in diameter, which is well within cosmic variance.

We investigate the geometry of a quantum universe with the topology of the four-torus. The study of noncontractible geodesic loops reveals that a typical quantum geometry consists of a small semiclassical toroidal bulk part, dressed with many outgrowths, which contain most of the four-volume and which have almost spherical topologies, but nevertheless are quite fractal.

Recently it was shown that the scaling dimension of the operator ${\varphi }^n$ in $\lambda (\overline{\varphi }\varphi {)}^2$ theory may be computed semiclassically at the Wilson-Fisher fixed point in $d=4-\epsilon$, for generic values of $\lambda n$, and this was verified to two loop order in perturbation theory at leading and subleading $n$. In subsequent work, this result was generalized to operators of fixed charge $\overline{Q}$ in $O(N)$ theory and verified up to three loops in perturbation theory at leading and subleading $\overline{Q}$. Here we extend this verification to four loops in $O(N)$ theory, once again at leading and subleading $\overline{Q}$. We also investigate the strong-coupling regime.

We trace what happens with asymptotically free behavior of the running coupling in ${\varphi }^3$ theory in six-dimensional spacetime, if to compactify two spatial dimensions on a 2D closed manifold. The result can be considered as an effective 4D theory of infinitely many KK-type scalar fields with triple interactions. The effective dimensional coupling constant inherits running to zero at high mass scales in a modified form depending on the size of the compact manifold. Some physical implications are discussed.

The procedure underlying the matching of 1-form (tetrad) fields in theories possessing absolute parallelism—$f(T)$ gravity being within this category—is addressed and exemplified. We show that the remnant symmetries of the intervening spaces play a central role in the process, because the knowledge of the remnant group of local Lorentz transformations enables one to perform rotations and/or boosts in order to ${\mathcal{C}}^1$-match the corresponding tetrads on the junction surface. This automatically ensures the continuity of the Weitzenböck scalar there, even though this proves to be just a necessary condition in order to obtain a global parallelization of the spacetime.

We explore the cosmological viability of a theory of gravity defined by the Lagrangian $f(\mathcal{R})={\mathcal{R}}^{n(\mathcal{R})}$ in the Palatini formalism, where $n(\mathcal{R})$ is a dimensionless function of the Palatini scalar curvature $\mathcal{R}$ that interpolates between general relativity when $n(\mathcal{R})=1$ and a locally scale-invariant and superficially renormalizable theory when $n(\mathcal{R})=2$. We refer to this model as asymptotically Weyl-invariant gravity (AWIG). We analyze perhaps the simplest possible implementation of AWIG. A phase space analysis yields three fixed points with effective equations of state corresponding to de Sitter-, radiation-, and matter-dominated phases. An analysis of the deceleration parameter suggests our model is consistent with an early and late period of accelerated cosmic expansion, with an intermediate period of decelerated expansion. We show that the model contains no obvious curvature singularities. Therefore, AWIG appears to be cosmologically viable, at least for the simple implementation explored.