Recently, it has been shown that the vacuum state in QED is infinitely degenerate. Moreover, a transition among the degenerate vacua is induced in any nontrivial scattering process and determined from the associated soft factor. Conventional computations of scattering amplitudes in QED do not account for this vacuum degeneracy and therefore always give zero. This vanishing of all conventional QED amplitudes is usually attributed to infrared divergences. Here, we show that if these vacuum transitions are properly accounted for, the resulting amplitudes are nonzero and infrared finite. Our construction of finite amplitudes is mathematically equivalent to, and amounts to a physical reinterpretation of, the 1970 construction of Faddeev and Kulish.

We propose a model for $CP$-violating oscillations of neutral, heavy-flavor baryons into antibaryons at rates which are within a few orders of magnitude of their lifetimes. The flavor structure of the baryon violation suppresses neutron oscillations and baryon-number-violating nuclear decays to experimentally allowed rates. We also propose a scenario for producing such baryons in the early Universe via the out-of-equilibrium decays of a neutral particle, after hadronization but before nucleosynthesis. We find parameters where $CP$-violating baryon oscillations at a temperature of a few MeV could result in the observed asymmetry between baryons and antibaryons. Furthermore, part of the relevant parameter space for baryogenesis is potentially testable at Belle II via decays of heavy-flavor baryons into an exotic neutral fermion. The model introduces four new particles: three light Majorana fermions and a colored scalar. The lightest of these fermions is typically long lived on collider time scales and may be produced in decays of bottom and possibly charmed hadrons.

Nambu–Jona-Lasinio-type models are frequently employed as low-energy models in various research fields. With respect to the theory of the strong interaction, this class of models is indeed often used to analyze the structure of the phase diagram at finite temperature and quark chemical potential. The predictions from such models for the phase structure at finite quark chemical potential are of particular interest as this regime is difficult to access with lattice Monte Carlo approaches. In this work, we consider a Fierz-complete version of a Nambu–Jona-Lasinio model. By studying its renormalization group flow, we analyze in detail how Fierz-incomplete approximations affect the predictive power of such model studies. In particular, we investigate the curvature of the phase boundary at small chemical potential, the critical value of the chemical potential above which no spontaneous symmetry breaking occurs, and the possible interpretation of the underlying dynamics in terms of difermion-type degrees of freedom. We find that the inclusion of four-fermion channels other than the conventional scalar-pseudoscalar channel is not only important at large chemical potential but also leaves a significant imprint on the dynamics at small chemical potential as measured by the curvature of the finite-temperature phase boundary.

Results of a search for a long-range monopole-dipole coupling between the mass of the Earth and rubidium (Rb) nuclear spins are reported. The experiment simultaneously measures the spin precession frequencies of overlapping ensembles of ${}^{85}\mathrm{Rb}$ and ${}^{87}\mathrm{Rb}$ atoms contained within an evacuated, antirelaxation-coated vapor cell. The nuclear structure of the Rb isotopes makes the experiment particularly sensitive to spin-dependent interactions of the proton. The spin-dependent component of the gravitational energy of the proton in the Earth’s field is found to be smaller than $3\times {10}^{-18}\mathrm{eV}$, improving laboratory constraints on long-range monopole-dipole interactions by over 3 orders of magnitude.

We use public data from the CMS experiment to study the two-prong substructure of jets. The CMS open data are based on $31.8{\mathrm{pb}}^{-1}$ of 7 TeV proton-proton collisions recorded at the Large Hadron Collider in 2010, yielding a sample of 768,687 events containing a high-quality central jet with transverse momentum larger than 85 GeV. Using CMS’s particle flow reconstruction algorithm to obtain jet constituents, we extract the two-prong substructure of the leading jet using soft-drop declustering. We find good agreement between results obtained from the CMS open data and those obtained from parton shower generators, and we also compare to analytic jet substructure calculations performed to modified leading-logarithmic accuracy. Although the 2010 CMS open data do not include simulated data to help estimate systematic uncertainties, we use track-only observables to validate these substructure studies.

We investigate the universality of truncation schemes for Dyson-Schwinger equations developed for quantum chromodynamics in theories which differ from quantum chromodynamics only in the gauge group. Our specific choices are the gauge groups $SU(2)$ and $G_2$, for which lattice calculations at nonvanishing chemical potential are possible. Thus, corresponding calculations can provide benchmarks for testing calculations with functional equations. We calculate the quark and gluon propagators and determine the chiral and dual chiral condensates at vanishing density to determine the confinement/deconfinement and chiral transitions, respectively. We can reproduce the expected type of transitions in the quenched and unquenched cases. In general, all three theories react very similarly to modifications of the employed model for the quark-gluon vertex.

We find double-copy relations between classical radiating solutions in Yang-Mills theory coupled to dynamical color charges and their counterparts in a cubic bi-adjoint scalar field theory which interacts linearly with particles carrying bi-adjoint charge. The particular color-to-kinematics replacements we employ are motivated by the Bern-Carrasco-Johansson double-copy correspondence for on-shell amplitudes in gauge and gravity theories. They are identical to those recently used to establish relations between classical radiating solutions in gauge theory and in dilaton gravity. Our explicit bi-adjoint solutions are constructed to second order in a perturbative expansion, and map under the double copy onto gauge theory solutions which involve at most cubic gluon self-interactions. If the correspondence is found to persist to higher orders in perturbation theory, our results suggest the possibility of calculating gravitational radiation from colliding compact objects, directly from a scalar field with vastly simpler (purely cubic) Feynman vertices.

We report on an all-sky search for periodic gravitational waves in the frequency band 20–475 Hz and with a frequency time derivative in the range of $[-1.0,+0.1]\times {10}^{-8}\mathrm{Hz}/\mathrm{s}$. Such a signal could be produced by a nearby spinning and slightly nonaxisymmetric isolated neutron star in our galaxy. This search uses the data from Advanced LIGO’s first observational run, O1. No periodic gravitational wave signals were observed, and upper limits were placed on their strengths. The lowest upper limits on worst-case (linearly polarized) strain amplitude $h_0$ are $\sim 4\times {10}^{-25}$ near 170 Hz. For a circularly polarized source (most favorable orientation), the smallest upper limits obtained are $\sim 1.5\times {10}^{-25}$. These upper limits refer to all sky locations and the entire range of frequency derivative values. For a population-averaged ensemble of sky locations and stellar orientations, the lowest upper limits obtained for the strain amplitude are $\sim 2.5\times {10}^{-25}$.

We present an upgraded calculation of the effects of resonance-continuum interference for the Higgs boson decaying to two photons at the Large Hadron Collider, at next-to-leading order in the strong coupling ${\alpha }_{\mathrm{S}}$, $\mathcal{O}({\alpha }_{\mathrm{S}}^3)$, and including transverse-momentum ($q_T$) resummation at next-to-leading logarithmic accuracy. We study the importance of the interference contribution in different transverse-momentum regions, with a particular focus on the low-$q_T$ region $q_T^2\ll Q^2$ (with $Q^2$ being the invariant diphoton mass) where resummation becomes essential for a reliable calculation.

We present the perturbative renormalization group functions of $O(n)$-symmetric ${\varphi }^4$ theory in $4-2ϵ$ dimensions to the sixth loop order in the minimal subtraction scheme. In addition, we estimate diagrams without subdivergences up to 11 loops and compare these results with the asymptotic behavior of the beta function. Furthermore we perform a resummation to obtain estimates for critical exponents in three and two dimensions.

We study the finite temperature phase structure for three-flavor QCD with a focus on locating the critical point, which separates the crossover and the first order phase transition region in the chiral regime of the Columbia plot. In this study, we employ the Iwasaki gauge action and the nonperturvatively $\mathrm{O}(a)$ improved Wilson-Clover fermion action. We discuss the finite size scaling analysis, including the mixing of magnetizationlike and energylike observables. We carry out the continuum extrapolation of the critical point using newly generated data at the $N_{\mathrm{t}}=8$, 10 and estimate the upper bound of the critical pseudoscalar meson mass $m_{\mathrm{PS},\mathrm{E}}\lesssim 170\mathrm{MeV}$ and the critical temperature $T_{\mathrm{E}}=134(3)\mathrm{MeV}$. Our estimate of the upper bound is derived from the existence of the critical point as an edge of the first order phase transition while that of the staggered-type fermions with smearing is based on its absence.

We explore oscillations of the solar ${}^8\mathrm{B}$ neutrinos in the Earth in detail. The relative excess of night ${\nu }_e$ events (the day-night asymmetry) is computed as function of the neutrino energy and the nadir angle $\eta$ of its trajectory. The finite energy resolution of the detector causes an important attenuation effect, while the layer-like structure of the Earth density leads to an interesting parametric suppression of the oscillations. Different features of the $\eta -$ dependence encode information about the structure (such as density jumps) of the Earth density profile; thus measuring the $\eta$ distribution allows the scanning of the interior of the Earth. We estimate the sensitivity of the DUNE experiment to such measurements. About 75 neutrino events are expected per day in 40 kt. For high values of $\mathrm{\Delta }{m}_{21}^2$ and $E_{\nu }>11\mathrm{MeV}$, the corresponding D-N asymmetry is about 4% and can be measured with 15% accuracy after 5 years of data taking. The difference of the D-N asymmetry between high and low values of $\mathrm{\Delta }{m}_{21}^2$ can be measured at the $4\sigma$ level. The relative excess of the ${\nu }_e$ signal varies with the nadir angle up to 50%. DUNE may establish the existence of the dip in the $\eta -$ distribution at the $(2–3)\sigma$ level.

We report measurements by the T2K experiment of the parameters ${\theta }_{23}$ and $\mathrm{\Delta }{m}_{32}^2$ governing the disappearance of muon neutrinos and antineutrinos in the three-flavor neutrino oscillation model. Utilizing the ability of the experiment to run with either a mainly neutrino or a mainly antineutrino beam, the parameters are measured separately for neutrinos and antineutrinos. Using $7.482\times 10^{20}$ POT in neutrino running mode and $7.471\times 10^{20}$ POT in antineutrino mode, T2K obtained ${\sin }^2({\theta }_{23})=0.51_{-0.07}^{+0.08}$ and $\mathrm{\Delta }{m}_{32}^2=2.53_{-0.13}^{+0.15}\times {10}^{-3}{\mathrm{eV}}^2/{\mathrm{c}}^4$ for neutrinos, and ${\sin }^2({\overline{\theta }}_{23})=0.42_{-0.07}^{+0.25}$ and ${\mathrm{\Delta }{\overline{m}}^2}_{32}=2.55_{-0.27}^{+0.33}\times {10}^{-3}{\mathrm{eV}}^2/{\mathrm{c}}^4$ for antineutrinos (assuming normal mass ordering). No significant differences between the values of the parameters describing the disappearance of muon neutrinos and antineutrinos were observed.

We construct a generalization of Witten’s Kaluza-Klein instanton, where a higher-dimensional sphere (rather than a circle as in Witten’s instanton) collapses to zero size and the geometry terminates at a bubble of nothing, in a low energy effective theory of M theory. We use the solution to exhibit the instability of nonsupersymmetric ${\mathrm{AdS}}_5$ vacua in M theory compactified on positive Kähler-Einstein spaces, providing further evidence for the recent conjecture that any nonsupersymmetric anti–de Sitter vacuum supported by fluxes must be unstable.

We present new measurements of the free-streaming of warm dark matter (WDM) from Lyman-$\alpha$ flux-power spectra. We use data from the medium resolution, intermediate redshift XQ-100 sample observed with the X-shooter spectrograph ($z=3–4.2$) and the high-resolution, high-redshift sample used in Viel et al. (2013) obtained with the HIRES/MIKE spectrographs ($z=4.2–5.4$). Based on further improved modelling of the dependence of the Lyman-$\alpha$ flux-power spectrum on the free-streaming of dark matter, cosmological parameters, as well as the thermal history of the intergalactic medium (IGM) with hydrodynamical simulations, we obtain the following limits, expressed as the equivalent mass of thermal relic WDM particles. The XQ-100 flux power spectrum alone gives a lower limit of 1.4 keV, the re-analysis of the HIRES/MIKE sample gives 4.1 keV while the combined analysis gives our best and significantly strengthened lower limit of 5.3 keV (all $2\sigma$ C.L.). The further improvement in the joint analysis is partly due to the fact that the two data sets have different degeneracies between astrophysical and cosmological parameters that are broken when the data sets are combined, and more importantly on chosen priors on the thermal evolution. These results all assume that the temperature evolution of the IGM can be modeled as a power law in redshift. Allowing for a nonsmooth evolution of the temperature of the IGM with sudden temperature changes of up to 5000 K reduces the lower limit for the combined analysis to 3.5 keV. A WDM with smaller thermal relic masses would require, however, a sudden temperature jump of 5000 K or more in the narrow redshift interval $z=4.6–4.8$, in disagreement with observations of the thermal history based on high-resolution resolution Lyman-$\alpha$ forest data and expectations for photo-heating and cooling in the low density IGM at these redshifts.

The charge asymmetry due to higher-order QED corrections in elastic lepton-proton scattering is estimated without employing the ultrarelativistic approximation. Our calculation is performed by generalizing the soft-photon approximation approach suggested by Tsai. Corresponding loop integrals that take a form of Passarino-Veltman scalar tree-point functions are calculated analytically without neglecting the mass of the lepton. Our results provide model-independent charge asymmetry predictions for scattering of unpolarized and massive leptons on proton targets. These predictions can be used in corresponding experiments to determine the contribution coming from model-dependent hard two-photon exchange processes.

We analyze commonly used expressions for computing the nucleon electric dipole form factors (EDFF) $F_3$ and moments (EDM) on a lattice and find that they lead to spurious contributions from the Pauli form factor $F_2$ due to inadequate definition of these form factors when parity mixing of lattice nucleon fields is involved. Using chirally symmetric domain wall fermions, we calculate the proton and the neutron EDFF induced by the $CP$-violating quark chromo-EDM interaction using the corrected expression. In addition, we calculate the electric dipole moment of the neutron using a background electric field that respects time translation invariance and boundary conditions, and we find that it decidedly agrees with the new formula but not the old formula for $F_3$. Finally, we analyze some selected lattice results for the nucleon EDM and observe that after the correction is applied, they either agree with zero or are substantially reduced in magnitude, thus reconciling their difference from phenomenological estimates of the nucleon EDM.

We calculate the double-spin asymmetries $A_{\mathrm{LL}}$ for the processes $\ell N\to hX$ and $\ell N\to \text{jet}X$ at next-to-leading order accuracy in perturbative QCD. We compare our theoretical results for $A_{\mathrm{LL}}$ to data from the SLAC E155 experiment, finding only partially satisfactory agreement. We conclude that measurements of $A_{\mathrm{LL}}$ and the relevant polarized and unpolarized cross sections should be performed at the present-day fixed-target lepton scattering experiments, as well as at a future electron ion collider, in order to verify our understanding of this process. We present predictions of the longitudinal double-spin asymmetries for these experiments.

In this work we present and analyze a new class of coordinate representations of de Sitter and anti–de Sitter spacetimes for which the metrics are diagonal and (typically) static and axially symmetric. Contrary to the well-known forms of these fundamental geometries, that usually correspond to a $1+3$ foliation with the 3-space of a constant spatial curvature, the new metrics are adapted to a $2+2$ foliation, and are warped products of two 2-spaces of constant curvature. This new class of (anti–)de Sitter metrics depends on the value of cosmological constant $\Lambda$ and two discrete parameters $+1,0,-1$ related to the curvature of the 2-spaces. The class admits 3 distinct subcases for $\Lambda >0$ and 8 subcases for $\Lambda <0$. We systematically study all these possibilities. In particular, we explicitly present the corresponding parametrizations of the (anti–)de Sitter hyperboloid, visualize the coordinate lines and surfaces within the global conformal cylinder, investigate their mutual relations, present some closely related forms of the metrics, and give transformations to standard de Sitter and anti–de Sitter metrics. Using these results, we also provide a physical interpretation of $B$-metrics as exact gravitational fields of a tachyon.

The small-scale crisis, discrepancies between observations and $N$-body simulations, may imply suppressed matter fluctuations on subgalactic distance scales. Such a suppression could be caused by some early-universe mechanism (e.g., broken scale invariance during inflation), leading to a modification of the primordial power spectrum at the onset of the radiation-domination era. Alternatively, it may be due to nontrivial dark-matter properties (e.g., new dark-matter interactions or warm dark matter) that affect the matter power spectrum at late times, during radiation domination, after the perturbations reenter the horizon. We show that early- and late-time suppression mechanisms can be distinguished by measurement of the $\mu$ distortion to the frequency spectrum of the cosmic microwave background. This is because the $\mu$ distortion is suppressed, if the power suppression is primordial, relative to the value expected from the dissipation of standard nearly scale-invariant fluctuations. We emphasize that the standard prediction of the $\mu$ distortion remains unchanged in late-time scenarios even if the dark-matter effects occur before or during the era (redshifts $5\times 10^4\lesssim z\lesssim 2\times 10^6$) at which $\mu$ distortions are generated.