Number Of Flavors Research Articles

Gravitational wave footprints from Higgs-portal scalegenesis with multiple dark chiral scalars* *Supported in part by the National Science Foundation of China (NSFC) (11747308, 11975108, 12047569), the Seeds Funding of Jilin University (S.M.), and Toyama First Bank, Ltd (H.I.)

We discuss the gravitational wave (GW) spectra predicted from the electroweak scalegenesis of the Higgs portal type with a large number of dark chiral flavors, which many flavor QCD would underlie and give the dynamical explanation of the negative Higgs portal coupling required to trigger the electroweak symmetry breaking. We employ the linear-sigma model as the low-energy description of dark many flavor QCD and show that the model undergoes ultra-supercooling due to the produced strong first-order thermal phase transition along the (approximately realized) flat direction based on the Gildener-Weinberg mechanism. Passing through evaluation of the bubble nucleation/percolation, we address the reheating and relaxation processes, which are generically non-thermal and nonadiabatic. Parametrizing the reheating epoch in terms of the e-folding number, we propose proper formulae for the redshift effects on the GW frequencies and signal spectra. It then turns out that the ultra-supercooling predicted from the Higgs-portal scalegenesis generically yields none of GW signals with the frequencies as low as nano Hz, unless the released latent heat is transported into another sector other than reheating the universe. Instead, models of this class prefer to give the higher frequency signals and still keeps the future prospected detection sensitivity, like at LISA, BBO, and DECIGO, etc. We also find that with large flavors in the dark sector, the GW signals are made further smaller and the peak frequencies higher. Characteristic phenomenological consequences related to the multiple chiral scalars include the prediction of dark pions with the mass much less than TeV scale, which is also briefly addressed.

Remarks on QCD4 with fundamental and adjoint matter

We study 4-dimensional SU(N) gauge theory with one adjoint Weyl fermion and fundamental matter — either bosonic or fermionic. Symmetries, their ’t Hooft anomalies, and the Vafa-Witten-Weingarten theorems strongly constrain the possible bulk phases. The first part of the paper is dedicated to a single fundamental fermion or boson. As long as the adjoint Weyl fermion is massless, this theory always possesses a ℤ2Nχ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {\\mathbb{Z}}_{2N}^{\\chi } $$\\end{document} chiral symmetry, which breaks spontaneously, supporting N vacua and domain walls between them for a generic mass of the matter fields. We argue, however, that the domain walls generically undergo a phase transition, and we establish the corresponding 3d gauge theories on the walls. The rest of the paper is dedicated to studying the multi-flavor fundamental matter. Here, the phases crucially depend on the ratio of the number of colors and the number of fundamental flavors. We also discuss the limiting scenarios of heavy adjoint and fundamentals, which align neatly with our current understanding of QCD and N\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\mathcal{N} $$\\end{document} = 1 super Yang-Mills theory.

Physics beyond the Standard Model with NA62

The NA62 experiment at CERN took data in 2016–2018 with the main goal of measuring the K + → νν̅ decay. The NA62 dataset is also exploited to search for light feebly interacting particles produced in kaon decays. Searches for K + → e + N and K + → μ + N decays, where N is a massive invisible particle, are performed. The N particle is assumed to be a heavy neutral lepton, and the results are expressed as upper limits of 𝒪(10-8) the neutrino mixing parameter |U14|2, where l = e,μ. Dedicated trigger lines were employed to collect di-lepton final states, which allowed stringent upper limits to be established for the rates lepton flavor and lepton number violating kaon decays. Upper limits on the rates of several K + decays violating lepton flavour and lepton number conservation, obtained by analysing this dataset, are presented here.

Anomalous dimensions in hypercubic theories

We perform a comprehensive perturbative study of the operator spectrum in multi-scalar theories with hypercubic global symmetry. This includes working out symmetry representations and their corresponding tensor structures. These structures are then used to compute the anomalous dimensions of scalar operators with up to four fields and arbitrary representations to six-loop order. Moreover, we determine one-loop anomalous dimensions for a large number of low-lying operators in the spectrum which include more powers of the fundamental field and/or insertions of derivatives. As an aside we show how projectors used in the conformal bootstrap can be conveniently reused in computations of anomalous dimensions. The results of our study are of use to the conformal bootstrap. They also illuminate features of conformal perturbation theory and the large n expansion. Our results may be of interest for various crossover phenomena in statistical field theory. In total, we compute the scaling dimension of more than 300 operators, of which 16 are computed to six-loops. Our analysis is exhaustive with respect to group theory up to rank 4 for any number of flavours n, and also exhaustive with respect to which representations exist for n ⩽ 4.

Exploring Seiberg-like dualities with eight supercharges

We propose a family of IR dualities for 3d N\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\mathcal{N} $$\\end{document} = 4 U(N) SQCD with Nf fundamental flavors and P Abelian hypermultiplets i.e. P hypermultiplets in the determinant representation of the gauge group. These theories are good in the Gaiotto-Witten sense if the number of fundamental flavors obeys the constraint Nf≥ 2N − 1 with generic P ≥ 1, and in contrast to the standard U(N) SQCD, they do not admit an ugly regime. The IR dualities in question arise in the window Nf = 2N + 1, 2N, 2N − 1, with P = 1 in the first case and generic P ≥ 1 for the others. The dualities involving Nf = 2N ± 1 are characterized by an IR enhancement of the Coulomb branch global symmetry on one side of the duality, such that the rank of the emergent global symmetry group is greater than the rank of the UV global symmetry. The dual description makes the rank of this emergent global symmetry manifest in the UV. In addition, one can read off the emergent global symmetry itself from the dual quiver. We show that these dualities are related by certain field theory operations and assemble themselves into a duality web. Finally, we show that the U(N) SQCDs with Nf≥ 2N − 1 and P Abelian hypers have Lagrangian 3d mirrors, and this allows one to explicitly write down the 3d mirror associated with a given IR dual pair. This paper is the first in a series of four papers on 3d N\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\mathcal{N} $$\\end{document} = 4 Seiberg-like dualities.

The local SYK model and its triple-scaling limit

We study a model of fermions with random couplings similar to conventional SYK with N number of flavours of fermions, at large N. Unlike the conventional SYK model, which has all-to-all couplings, the model we study, which we call local SYK, has a much less number of random couplings, just N in number and with only local interactions. It is shown that there exists a limit in which the local SYK model can be solved using the chord diagram techniques, analogous to the double-scaled limit of conventional SYK. This limit corresponds to taking the size of the fermion coupling terms, q, to scale linearly with N. A further triple-scaling limit is taken to analyze the low energy limit and it is shown that the OTOCs saturate the chaos bound, paralleling the analysis in the conventional SYK.

Pauli-term-induced fixed points in d-dimensional QED

We explore the fixed-point structure of QED-like theories upon the inclusion of a Pauli spin-field coupling. We concentrate on the fate of UV-stable fixed points recently discovered in d=4\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$d=4$$\\end{document} spacetime dimensions upon generalizations to lower as well as higher dimensions for an arbitrary number of fermion flavors Nf.\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$N_{\ ext {f}}.$$\\end{document} As an overall trend, we observe that going away from d=4\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$d=4$$\\end{document} dimensions and increasing the flavor number tends to destabilize the non-Gaussian fixed points discovered in four spacetime dimensions. A notable exception is a non-Gaussian fixed point at finite Pauli spin-field coupling but vanishing gauge coupling, which also remains stable down to d=3\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$d=3$$\\end{document} dimensions and for small flavor numbers. This includes also the range of degrees of freedom used in effective theories of layered condensed-matter systems. As an application, we construct renormalization group trajectories that emanate from the non-Gaussian fixed point and approach a long-range regime in the conventional QED3\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${}_3$$\\end{document} universality class that is governed by the interacting (quasi) fixed point in the gauge coupling.

On the dynamical origin of the η′ potential and the axion mass

We investigate the dynamics responsible for generating the potential of the η′, the (would-be) Goldstone boson associated with the anomalous axial U(1) symmetry of QCD. The standard lore posits that pure QCD dynamics generates a confining potential with a branched structure as a function of the θ angle, and that this same potential largely determines the properties of the η′ once fermions are included. Here we test this picture by examining a supersymmetric extension of QCD with a small amount of supersymmetry breaking generated via anomaly mediation. For pure SU(N) QCD without flavors, we verify that there are N branches generated by gaugino condensation. Once quarks are introduced, the flavor effects qualitatively change the strong dynamics of the pure theory. For F flavors we find |N − F| branches, whose dynamical origin is gaugino condensation in the unbroken subgroup for F < N – 1, and in the dual gauge group for F > N + 1. For the special cases of F = N – 1, N, N + 1 we find no branches and the entire potential is consistent with being a one-instanton effect. The number of branches is a simple consequence of the selection rules of an anomalous U(1)R symmetry. We find that the η′ mass does not vanish in the large N limit for fixed F/N, since the anomaly is non-vanishing. The same dynamics that is responsible for the η′ potential is also responsible for the axion potential. We present a simple derivation of the axion mass formula for an arbitrary number of flavors.

Comparative study of the heavy-quark dynamics with the Fokker-Planck equation and the Plastino-Plastino equation

The Fokker-Planck Equation (FPE) is a fundamental tool for the investigation of kinematic aspects of a wide range of systems. The Plastino-Plastino Equation (PPE) is the correct generalization describing the kinematic evolution of complex systems consistent with q-statistics. In the present work, we use this particular problem to compare the results obtained with the FPE and the PPE, and discuss the different aspects of the dynamical evolution of the system according to the solutions for each equation. We observe clear differences in the solutions for all the cases studied here and discuss possible experimental investigations that can indicate which of those equations better describes the heavy-quark kinematics in the medium. The results obtained here have implications in the study of anomalous diffusion in porous and granular media, in Cosmology and Astrophysics. The obtained results reinforce the validity of the relation (q−1)−1=(11/3)Nc−(4/3)(Nf/2), where Nc and Nf are, respectively, the number of colours and the effective number of flavours. This equation was recently established in the context of a fractal approach to QCD in the non-perturbative regime.

The QCD phase diagram in the space of imaginary chemical potential via ’t Hooft anomalies

The QCD phase diagram in the space of temperature and imaginary baryon chemical potential has been an interesting subject in numerical lattice QCD simulations because of the absence of the sign problem and its deep structure related to confinement/deconfinement. We study constraints on the phase diagram by using an ’t Hooft anomaly. The relevant anomaly is an anomaly in the space of imaginary chemical potential. We compute it in the UV, and discuss how it is matched by the pion effective field theory at low temperatures. Then we study implications of the anomaly to the phase diagram. There must be a line of phase transition studied in the past by Roberge and Weiss such that the expectation value of the Polyakov loop is not smooth when we cross the line. Moreover, if the greatest common divisor of the color and flavor numbers is greater than one, the phase transition across the Roberge-Weiss line must be either a first order phase transition, or a second order phase transition described by a nontrivial interacting three-dimensional CFT.

Characterization of Ad Libitum Use Behavior of On! Nicotine Pouches.

Objectives: Actual use of nicotine pouch products is not well studied. The objectives of this study were to characterize on ® nicotine pouch (Test Products (TP)) use behavior, including association with cigarette and smokeless tobacco (ST) product use. Methods: Adults who smoke cigarettes (AS) and/or adults who use ST (ASTU) (N=1147) that were not planning to quit and had expressed interest in trying and using TP after a 5-day trial were offered ad libitum use of TPs (7 flavors at 5 nicotine levels) for 6 weeks. Results: Participants used a median of ~5-6 pouches/day of a variety of flavors and nicotine levels. In the final week of the study, 27% of AS and 71% of ASTU reported no use of cigarettes or ST respectively, while reporting continued use of TPs. Additionally, 39% of AS and 14% of ASTU reduced consumption of cigarettes or ST products respectively by 50%-99%, compared to reported use at screening. We found a statistically significant inverse relationship between TP flavor varieties and number of cigarettes/ST. Conclusions: These data suggest that TPs can be potential substitutes for cigarettes/ST products, and complete switching may offer harm reduction potential for AS and ASTU not interested in quitting.

Chiral phase transition of a dense, magnetized and rotating quark matter

We investigate the chiral symmetry restoration/breaking of a dense, magnetized and rotating quark matter within the Nambu Jona–Lasinio model including Nf=2 and Nc=3 numbers of flavors and colors, respectively. Imposing the spectral boundary conditions as well as the positiveness of energy levels lead to a correlation between the magnetic and rotation fields such that strongly magnetized plasma can not rotate anymore. We solve the gap equation at zero and finite temperature. At finite temperature and baryon chemical potential μB, we sketch the phase diagrams Tc(μB) and Tc(RΩ) in different cases. As a result, we always observe inverse-rotational catalysis mean to decrease Tc by increasing RΩ. But the magnetic field has a more complex structure in the phase diagram. For slowly rotating plasma, we find that Tc decreases by increasing eB, while in the fast rotating plasma we see that Tc increases by increasing eB. Also, we locate exactly the position of Critical End Point by solving the equations of first and second derivatives of effective action with respect to the order parameters, simultaneously.

Magnetic catalysis in the ( 2+1 )-dimensional Gross-Neveu model

We study the Gross-Neveu model in $2+1$ dimensions in an external magnetic field $B$. We first summarize known mean-field results, obtained in the limit of large flavor number $N_\mathrm{f}$, before presenting lattice results using the overlap discretization to study one reducible fermion flavor, $N_\mathrm{f}=1$. Our findings indicate that the magnetic catalysis phenomenon, i.e., an increase of the chiral condensate with the magnetic field, persists beyond the mean-field limit for temperatures below the chiral phase transition and that the critical temperature grows with increasing magnetic field. This is in contrast to the situation in QCD, where the broken phase shrinks with increasing $B$ while the condensate exhibits a non-monotonic $B$-dependence close to the chiral crossover, and we comment on this discrepancy. We do not find any trace of inhomogeneous phases induced by the magnetic field.

Enhanced nematicity emerging from higher-order Van Hove singularities

Motivated by the experimental identification of a higher-order Van Hove singularity (VHS) in $A{\text{V}}_{3}{\mathrm{Sb}}_{5}$ kagome metals, we study electronic instabilities of two-dimensional lattice models with higher-order VHS and flavor degeneracy. In contrast to conventional VHSs, the larger power-law density of states and the weaker nesting propensity of higher-order VHSs conspire together to generate distinct competing instabilities. After discussing the occurrence of higher-order VHSs on square and kagome lattice models, we perform unbiased renormalization group calculations to study competing instabilities and find a rich phase diagram containing ferromagnetism, antiferromagnetism, superconductivity, and Pomeranchuk orders. Remarkably, there is a generic transition from superconductivity to a $d$-wave Pomeranchuk order with increasing flavor number. Implications for the intriguing quantum states of $A{\text{V}}_{3}{\mathrm{Sb}}_{5}$ kagome metals are also discussed.

Anomalous dimensions from soft Regge constants

Using an effective field theory (EFT) formalism for forward scattering, we reconsider the factorization of 2 → 2 scattering amplitudes in the Regge limit. Expanding the amplitude in gauge invariant operators labelled by the number of Glauber exchanges, allows us to further factorize the standard impact factors into separate collinear and soft functions. The soft functions are universal, and describe radiative corrections to the Reggeized gluon states exchanged by the collinear projectiles. Remarkably, we find that the one-loop soft function for the single Reggeized gluon state is given to mathcal{O} (ϵ) in terms of the two-loop cusp and two-loop rapidity anomalous dimensions. We argue that this iterative structure follows from the simple action of crossing symmetry in the forward scattering limit, which in the EFT allows us to replace the divergent part of a soft loop by a much simpler Glauber loop. We use this correspondence to provide a simple calculation of the two-loop Regge trajectory using the EFT. We then explore its implications at higher perturbative orders, and derive the maximally matter dependent contributions to the Regge trajectory to all loop orders, i.e. the terms sim {alpha}_s^{k+1}{n}_f^k for any k, where nf is the number of massless flavors. These simplifications suggests that the EFT approach to the Regge limit will be helpful to explore and further understand the structure of the Regge limit.

Construction of irregular conformal/W block and flavor mass relations of [formula omitted] SUSY gauge theory from the An−1 quiver matrix model

A sequence of massive scaling limits of the β-deformed An−1 quiver matrix model that keeps the size of the matrices finite and that corresponds to the Nf=2n→2n−1,2n−2 limits on the number of flavors at 4d su(n)N=2 SUSY gauge theory side is carried out to provide us with the integral representation of su(n) irregular conformal/W block. The original paths are naturally deformed into those in the complex plane, permitting us to convert into an su(n) extension of the unitary matrix model of GWW type with a set of log potentials for all species of eigenvalues. Looking at the region in the parameter space that enjoys the maximal symmetry of the model, we derive a set of relations among the mass parameters which may serve as evidence for the existence of the Argyres-Douglas critical hypersurface.

Four-loop massive cusp anomalous dimension in QCD: A calculation from asymptotics

I present a general method for determining the massive cusp anomalous dimension in QCD to a very high degree of accuracy using its asymptotic behavior at small and large quark velocities. I show that the method works exceedingly well at two and three loops where exact results are already known. I then present a calculation of the massive cusp anomalous dimension using its asymptotics at four loops, and I provide a detailed study of the results for different values of the number of flavors and for separate color structures. The method can be further extended and applied to higher numbers of loops.

Formula omitted]) polarized heavy flavor corrections to deep-inelastic scattering at Q2 ≫ m2

We calculate the quarkonic O(αs2) massive operator matrix elements ΔAQg(N),ΔAQqPS(N) and ΔAqq,QNS(N) for the twist–2 operators and the associated heavy flavor Wilson coefficients in polarized deeply inelastic scattering in the region Q2≫m2 to O(ε) in the case of the inclusive heavy flavor contributions. The evaluation is performed in Mellin space, without applying the integration-by-parts method. The result is given in terms of harmonic sums. This leads to a significant compactification of the operator matrix elements and massive Wilson coefficients in the region Q2≫m2 derived previously in [1], which we partly confirm, and also partly correct. The results allow to determine the heavy flavor Wilson coefficients for g1(x,Q2) to O(αs2) for all but the power suppressed terms ∝(m2/Q2)k,k≥1. The results in momentum fraction z-space are also presented. We also discuss the small x effects in the polarized case. Numerical results are presented. We also compute the gluonic matching coefficients in the two–mass variable flavor number scheme to O(ε).

Searches for lepton flavour and lepton number violating K + decays at the NA62 experiment

The NA62 experiment at CERN collected the world’s largest dataset of charged kaon decays to di-lepton final states in 2016-2018, using dedicated trigger lines. Upper limits on the rates of several K + decays violating lepton flavour and lepton number conservation, obtained by analysing this dataset, are reported.

Electron-Hole Asymmetry of Quantum Collective Excitations in High-Tc Copper Oxides

We carry out a systematic study of collective spin- and charge excitations for the canonical single-band Hubbard, $t$-$J$-$U$, and $t$-$J$ models of high-temperature copper-oxide superconductors, both on electron- and hole-doped side of the phase diagram. Recently developed variational wave function approach, combined with the expansion in inverse number of fermionic flavors, is employed. All three models exhibit a substantial electron-hole asymmetry of magnetic excitations, with a robust paramagnon emerging for hole-doping, in agreement with available resonant inelastic $x$-ray scattering data for the cuprates. The $t$-$J$ model yields additional high-energy peak in the magnetic spectrum that is not unambiguously identified in spectroscopy. For all considered Hamiltonians, the dynamical charge susceptibility contains a coherent mode for both hole- and electron doping, with overall bandwidth renormalization controlled by the on-site Coulomb repulsion. Away from the strong-coupling limit, the antiferromagnetic ordering tendency is more pronounced on electron-doped side of the phase diagram.