We put the upper bound on the gravitational waves (GWs) induced by the scalar-field fluctuations during the inflation. In particular, we focus on the case where the scalar fluctuations get amplified within some subhorizon scales by some mechanism during the inflation. Since the energy conservation law leads to the upper bound on the energy density of the scalar fluctuations, the amplitudes of the scalar fluctuations are constrained and therefore the induced GWs are also. Taking into account this, we derive the upper bound on the induced GWs. As a result, we find that the GW power spectrum must be ${\mathcal{P}}_h\lesssim \mathcal{O}({\epsilon }^2(k/k_{*}{)}^2)$ up to the logarithmic factor, where $\epsilon$ is the slow-roll parameter and $k_{*}$ is the peak scale of the scalar-field fluctuations.

We present a consistent framework to set limits on properties of light sterile neutrinos coupled to all three active neutrinos using a combination of the latest cosmological data and terrestrial measurements from oscillations, $\beta$-decay, and neutrinoless double-$\beta$-decay ($0\nu \beta \beta$) experiments. We directly constrain the full $3+1$ active-sterile mixing matrix elements $|U_{\alpha 4}{|}^2$, with $\alpha \in (e,\mu ,\tau )$, and the mass-squared splitting $\mathrm{\Delta }{m}_{41}^2\equiv m_4^2-m_1^2$. We find that results for a $3+1$ case differ from previously studied $1+1$ scenarios where the sterile is coupled to only one of the neutrinos, which is largely explained by parameter space volume effects. Limits on the mass splitting and the mixing matrix elements are currently dominated by the cosmological datasets. The exact results are slightly prior dependent, but we reliably find all matrix elements to be constrained below $|U_{\alpha 4}{|}^2\lesssim {10}^{-3}$. Short-baseline neutrino oscillation hints in favor of eV-scale sterile neutrinos are in serious tension with these bounds, irrespective of prior assumptions. We also translate the bounds from the cosmological analysis into constraints on the parameters probed by laboratory searches, such as $m_{\beta }$ or $m_{\beta \beta }$, the effective mass parameters probed by $\beta$-decay and $0\nu \beta \beta$ searches, respectively. When allowing for mixing with a light sterile neutrino, cosmology leads to upper bounds of $m_{\beta }<0.09\mathrm{eV}$ and $m_{\beta \beta }<0.07\mathrm{eV}$ at 95% CL, more stringent than the limits from current laboratory experiments.

We reconstruct the neutrino mass as a function of redshift, $z$, from current cosmological data using both standard binned priors and linear spline priors with variable knots. Using cosmic microwave background temperature, polarization and lensing data, in combination with distance measurements from baryonic acoustic oscillations and supernovae, we find that the neutrino mass is consistent with $\sum m_{\nu }(z)=\mathrm{const}$. We obtain a larger bound on the neutrino mass at low redshifts coinciding with the onset of dark energy domination, $\sum m_{\nu }(z=0)<1.46\mathrm{eV}$ (95% CL). This result can be explained either by the well-known degeneracy between $\sum m_{\nu }$ and ${\mathrm{\Omega }}_{\mathrm{\Lambda }}$ at low redshifts, or by models in which neutrino masses are generated very late in the Universe. We finally convert our results into cosmological limits for models with nonrelativistic neutrino decay and find $\sum m_{\nu }<0.21\mathrm{eV}$ (95% CL), which would be out of reach for the KATRIN experiment.

In the model proposed by Bélanger, Delaunay, and Westhoff (BDW), a new sector consisting of vectorlike fermions and two complex scalars is charged under an extra Abelian symmetry $U(1{)}_X$. In this paper, we generalize the BDW model by introducing the kinetic mixing between the $U(1{)}_X$ and the standard model $U(1{)}_Y$ gauge fields. The new physics contributions to the muon anomalous magnetic moment and the Wilson coefficients $C_{9,10}^{{(}^{\prime })}$ are obtained analytically. We have explored the free parameter space of the model, taking into account various constraints on the muon $g-2$ using recent data from the E989 experiment at Fermilab, the lepton universality violation in terms of $R_K$ and $R_{K^{*}}$ and the branching ratios of the semileptonic decays, $B^{+}\to K^{+}{\mu }^{+}{\mu }^{-}$ and $B^0\to K^{*0}{\mu }^{+}{\mu }^{-}$, the LEP and LHC searches for sleptons and $Z^{\prime }$ boson, as well as the perturbative requirement. The viable parameter regions of the model are identified. In the presence of the gauge kinetic mixing term, those regions are enlarged and significantly deformed in comparison to the case with vanishing kinetic mixing. In the near future, the E989 experiment with the projected sensitivity will be able to test significant parts of the currently allowed parameter regions.

Dark matter searches using dual-phase xenon time-projection chambers (LXe-TPCs) rely on their ability to reject background electron recoils (ERs) while searching for signal-like nuclear recoils (NRs). ER response is typically calibrated using $\beta$-decay sources, such as tritium, but these calibrations do not characterize events accompanied by an atomic vacancy, as in solar neutrino scatters off inner-shell electrons. Such events lead to emission of x rays and Auger electrons, resulting in higher electron-ion recombination and thus a more NR-like response than inferred from $\beta$-decay calibration. We present a cross-calibration of tritium $\beta$-decays and ${}^{127}\mathrm{Xe}$ electron-capture decays (which produce inner-shell vacancies) in a small-scale LXe-TPC and give the most precise measurements to date of light and charge yields for the ${}^{127}\mathrm{Xe}$ $L$-shell electron-capture in liquid xenon. We observe a $6.9\sigma$ ($9.2\sigma$) discrepancy in the $L$-shell capture response relative to tritium $\beta$ decays, measured at a drift field of $363\pm 14\mathrm{V}/\mathrm{cm}$ ($258\pm 13\mathrm{V}/\mathrm{cm}$), when compared to simulations tuned to reproduce the correct $\beta$-decay response. In dark matter searches, use of a background model that neglects this effect leads to overcoverage (higher limits) for background-only multi-kiloton-year exposures, but at a level much less than the $1\text{−}\sigma$ experiment-to-experiment variation of the 90% C.L. upper limit on the interaction rate of a $50\mathrm{GeV}/c^2$ dark matter particle.

We investigate the consequences of elliptic leading singularities for the unitarity-based representations of two-loop amplitudes in planar, maximally supersymmetric Yang-Mills theory. We show that diagonalizing with respect to these leading singularities ensures that the integrand basis is termwise pure (suitably generalized, to the elliptic multiple polylogarithms, as necessary). We also investigate an alternative strategy based on diagonalizing a basis of integrands on differential forms; this strategy, while neither termwise Yangian-invariant nor pure, offers several advantages in terms of complexity.

We apply the new quantization scheme outlined in M. Becker and M. Reuter, Phys. Rev. D 102, 125001 (2020), to explore the influence which quantum vacuum fluctuations of the spacetime metric exert on the universes of quantum Einstein gravity, which is regarded an effective theory here. The scheme promotes the principle of background independence to the level of the regularized precursors of a quantum field theory (“approximants”) and severely constrains admissible regularization schemes. Without any tuning of parameters, we find that the zero point oscillations of linear gravitons on maximally symmetric spacetimes do not create the commonly expected cosmological constant problem of a cutoff-size curvature. On the contrary, metric fluctuations are found to reduce positive curvatures to arbitrarily tiny and ultimately vanishing values when the cutoff is lifted. This suggests that flat space could be the distinguished ground state of pure quantum gravity. Our results contradict traditional beliefs founded upon background-dependent calculations whose validity must be called into question therefore.

We study the possibility that an extended cosmic-ray leptonic and/or hadronic halo is at the origin of the large-scale gamma-ray emission detected from the Andromeda galaxy (M31). We consider a broad ensemble of nonhomogeneous diffusion scenarios and of cosmic-ray injection sources. We find that cosmic-ray electrons and protons could be, and very likely are, responsible for part, or all, of the gamma-ray emission from M31, including out to more than 100 kpc from the center of the galaxy. We also simulate possible emission from pulsars in M31 and consider the effect of regions of highly inefficient diffusion around cosmic-ray acceleration sites, as suggested by recent TeV halo observations with Cherenkov telescopes.

Quantum fluctuations can induce friction on a neutral but polarizable particle and cause it to radiate energy even if the particle is moving in free space filled with blackbody radiation and is not in contact with or close to any surface or other object. We explore the energetics of such a particle moving uniformly in vacuum, continuing our previous investigations of quantum friction. The intrinsic polarizability of the particle is considered to be purely real before it is dressed by radiation. The particle is then guaranteed to be in the nonequilibrium steady state (NESS), where it absorbs and emits energy at the same rate. We first calculate the quantum frictional power and force on the particle in the rest frame of the blackbody radiation from first principles, namely the Maxwell-Heaviside equations and the Lorentz force law. Then we provide a simpler method of obtaining the same quantities in the rest frame of the particle by using the principle of virtual work. The equivalence of the two approaches is illustrated. The formulas we derive for quantum vacuum frictional power and force are fully relativistic and applicable to finite temperature. In NESS, the quantum vacuum frictional force on the particle is shown to be a true drag, independent of the model for polarizability and the polarization state of the particle. Finally, we give an estimate of the quantum vacuum friction on a gold atom and comment on the feasibility of detecting such quantum vacuum frictional effects.

We study a model with a vector dark matter (DM) candidate interacting with the standard model (SM) charged leptons through a scalar portal. The dark matter candidate acquires mass when the complex scalar breaks an Abelian gauge symmetry spontaneously. The scalar interacts with the SM charged leptons through a dimension-6 operator. The scalar mediator induces elastic scattering of dark matter with electrons at tree level and also DM-nucleon interaction when the effects from scalar-Higgs mixing are taken into account. Given the recent results from Xenon1T upper bounds on DM-electron elastic scattering cross sections where the strongest sensitivity lies in the range $\sim \mathcal{O}(1)\mathrm{GeV}$, we find the viable space in the parameter space respecting constraints from the observed relic density, direct detection, muon $(g_{\mu }-2)$ anomaly, $e^{+}{e}^{-}$ colliders, electron beam-dump experiments and astrophysical observables. It is shown that the current upper bounds of Xenon1T on DM-electron interactions are partially sensitive to the regions in the viable parameter space which is already excluded by the electron beam-dump experiment, Orsay. We also find that there are viable DM particles with masses $\sim \mathcal{O}(1)\mathrm{GeV}$ evading the direct detection but standing well above the neutrino floor. Almost the same viable regions are found when we apply the direct detection upper limits on the DM-proton spin-independent cross section.

We provide a simple analysis of the big-bang nucleosynthesis (BBN) sensitivity to the light dark matter (DM) generated by the thermal freeze-in mechanism. It is shown that the ratio of the effective neutrino number shift $\mathrm{\Delta }{N}_{\nu }$ over the DM relic density $\omega \equiv \mathrm{\Omega }{h}^2$, denoted by $R_{\chi }\equiv \mathrm{\Delta }{N}_{\nu }/\omega$, cancels the decaying particle mass and the feeble coupling, rendering therefore a simple visualization of $\mathrm{\Delta }{N}_{\nu }$ at the BBN epoch in terms of the DM mass. This property drives one to conclude that the shift with a sensitivity of $\mathrm{\Delta }{N}_{\nu }\simeq \mathcal{O}(0.1)$ cannot originate from a single warm DM under the Lyman-$\alpha$ forest constraints. For the cold-plus-warm DM scenarios, where the Lyman-$\alpha$ constraints are diluted, the ratio $R_{\chi }$ can be potentially used to test the thermal freeze-in mechanism in generating a small warm component of DM and a possible excess at the level of $\mathrm{\Delta }{N}_{\nu }\simeq \mathcal{O}(0.01)$.

This work presents a lattice quantum chromodynamics (QCD) calculation of the nonperturbative Collins-Soper kernel, which describes the rapidity evolution of quark transverse-momentum-dependent parton distribution functions. The kernel is extracted at transverse momentum scales in the range $400\mathrm{MeV}<q_T<1.7\mathrm{GeV}$ in a calculation with dynamical fermions and quark masses corresponding to a larger-than-physical pion mass, $m_{\pi }=538(1)\mathrm{MeV}$. It is found that different approaches to extract the Collins-Soper kernel from the same underlying lattice QCD matrix elements yield significantly different results and uncertainty estimates, revealing that power corrections, such as those associated with higher-twist effects, and perturbative matching between quasi- and light-cone beam functions, cannot be neglected.

In this paper we compute masses and magnetic moments of heavy baryons and tetraquarks with one and two open heavy flavors in a unified framework of the MIT bag model. Using the parameters of the MIT bag model, we confirm that an extra binding energy, which is supposed to exist between heavy quarks ($c$ and $b$), and between heavy and strange quarks in literatures, is required to reconcile light hadrons with heavy hadrons. Numerical calculations are made for all light mesons and heavy hadrons (with one and two open heavy flavors) predicting the masses of doubly charmed baryons to be $M({\mathrm{\Xi }}_{cc})=3.604\mathrm{GeV}$, $M({\mathrm{\Xi }}_{cc}^{*})=3.714\mathrm{GeV}$, and that of the strange isosinglet tetraquark $ud\overline{s}\overline{c}$ with $J^P=0^{+}$ to be $M(ud\overline{s}\overline{c},0^{+})=2.934\mathrm{GeV}$. The state mixing due to chromomagnetic interaction is shown to be sizable for the strange scalar tetraquark $nn\overline{s}\overline{c}$.

The compressibility of magnetized quark matter is investigated in the SU(2) NJL model. The increases of the chemical potential and the temperature can reduce the compressibility, and lead to the much stiffer equation of state. The variation of the compressibility with the magnetic field will depend on the phase region. Due to the anisotropic structure, the compressibility is different in the directions parallel and perpendicular to the field. The discontinuity of longitudinal compressibility with the chemical potential and the temperature captures the signature of a first-order chiral phase transition and the crossover at high temperature. Moreover, the magnetic-field-and-temperature running coupling would have an important effect on the position of the phase transition. Under the lowest landau level approximation at zero temperature, the longitudinal compressibility has a direct inverse proportional relation to the magnetic field strength and the chemical potential square as ${\kappa }_{\mathrm{LLL},\chi }^{\parallel }\propto 1/(eB{\mu }^2)$.

We suggest to study the production mechanism and some details of the production properties to probe the structure of the $DD\pi$ resonance $T_{cc}$ recently observed by the LHCb Collaboration. If the resonance is produced as a four-quark state, one can find the corresponding signals via measurements on the production properties which are the same as those of ${\mathrm{\Xi }}_{cc}$, i.e., the similarity of $T_{cc}$ and ${\mathrm{\Xi }}_{cc}$ in the kinematics spectra, in the baryon number enhancement, and in the string effect, etc. The color connection of the preconfinement cluster in which the cc diquark pair hadronize to the $T_{cc}$ or ${\mathrm{\Xi }}_{cc}$ plays the key role for their similarity. Moreover, the production cross section of $T_{cc}$ in various rapidity regions and the production ratio between $T_{cc}$ to a different isospin state $T_{cc}^{\prime }$ (if it exists) are also important and clear tests. On the other hand, if $T_{cc}$ is produced as a hadron molecule, the measurement on the momentum correlation of $D{D}^{*}$ can be a key judgement, since it determines the production ratio. From the present available information, the calculated cross section with nonrelativistic hadron molecule model is about an order of magnitude lower than the experimental measurement.

We propose the inclusive semihard production, in proton-proton collisions, of two bottom-flavored hadrons, as well as that of a single bottom-flavored hadron accompanied by a light jet, as novel channels for the manifestation of stabilization effects of the high-energy resummation under next-to-leading-order corrections. Our formalism relies on a hybrid high-energy and collinear factorization, where the Balitsky-Fadin-Kuraev-Lipatov (BFKL) resummation of leading and next-to-leading energy logarithms is used together with collinear factorization. We present results for cross sections and azimuthal correlations differential in rapidity, which are widely recognized as standard observables used to hunt for distinctive signals of the BFKL dynamics. We propose the study of double differential distributions in the transverse momenta of final-state particles as a common basis to investigate the interplay of different kinds of resummation mechanisms.

We introduce a subsystem generalization of the spectral form factor via pseudoentropy, the von-Neumann entropy for the reduced transition matrix. We consider a transition matrix between the thermofield double state and its time-evolved state in two-dimensional conformal field theories, and study the time dependence of the pseudoentropy for a single interval. We show that the real part of the pseudoentropy behaves similarly to the spectral form factor; it starts from the thermal entropy, initially drops to the minimum, then it starts increasing, and then finally it approaches the vacuum entanglement entropy. We also study the theory dependence of its behavior by considering theories on a compact space.

The traditional clustering analyses of galaxy redshift surveys compress the clustering data into a set of late-time physical variables in a model-independent way. This approach has recently been extended by an additional shape variable encoding early-time physics information. We apply this new technique, ShapeFit, to SDSS-III BOSS data and show that it matches the constraining power of alternative, model-dependent approaches, which directly constrain the model’s parameters adopting a cosmological model ab initio. ShapeFit is $\sim 30$ times faster, model independent, naturally splits early- and late-time variables, and enables a better control of observational systematics.

In extensions of the Standard Model with no dimensionful parameters the electroweak phase transition can be delayed to temperatures of order 100 MeV. Then the chiral phase transition of QCD can proceed with six massless quarks. The top-quark condensate destabilizes the Higgs potential through the Yukawa interaction, triggering the electroweak transition. Based on the symmetries of massless QCD, it has been argued that the chiral phase transition is first order. We point out that the top-Higgs Yukawa interaction is nonperturbatively large at the QCD scale, and that its effect on the chiral phase transition may not be negligible, violating some of the symmetries of massless QCD. The remaining symmetries indicate that top quarks condense in a second-order phase transition, but top condensation might also be triggered by a first-order symmetry-breaking transition in the light-quark sector.

The concept of minimum length, widely accepted as a low-energy effect of quantum gravity, manifests itself in quantum mechanics through generalized uncertainty principles. Curved momentum space, on the other hand, is at the heart of similar applications such as doubly special relativity. We introduce a duality between theories yielding generalized uncertainty principles and quantum mechanics on nontrivial momentum space. In particular, we find canonically conjugate variables which map the former into the latter. In that vein, we explicitly derive the vielbein corresponding to a generic generalized uncertainty principle in $d$ dimensions. Assuming the predominantly used quadratic form of the modification, the curvature tensor in momentum space is proportional to the noncommutativity of the coordinates in the modified Heisenberg algebra. Yet, the metric is non-Euclidean even in the flat case corresponding to commutative space, because the resulting momentum basis is noncanonical. These insights are used to constrain the curvature and the deviation from the canonical basis.