No Arabic abstract
The popular $mathcal{AB}$/push-pull method for distributed optimization problem may unify much of the existing decentralized first-order methods based on gradient tracking technique. More recently, the stochastic gradient variant of $mathcal{AB}$/Push-Pull method ($mathcal{S}$-$mathcal{AB}$) has been proposed, which achieves the linear rate of converging to a neighborhood of the global minimizer when the step-size is constant. This paper is devoted to the asymptotic properties of $mathcal{S}$-$mathcal{AB}$ with diminishing stepsize. Specifically, under the condition that each local objective is smooth and the global objective is strongly-convex, we first present the boundedness of the iterates of $mathcal{S}$-$mathcal{AB}$ and then show that the iterates converge to the global minimizer with the rate $mathcal{O}left(1/sqrt{k}right)$. Furthermore, the asymptotic normality of Polyak-Ruppert averaged $mathcal{S}$-$mathcal{AB}$ is obtained and applications on statistical inference are discussed. Finally, numerical tests are conducted to demonstrate the theoretic results.
We use an isomorphism established by Langenbruch between some sequence spaces and weighted spaces of generalized functions to give sufficient conditions for the (Beurling type) space ${mathcal S}_{(M_p)}$ to be nuclear. As a consequence, we obtain that for a weight function $omega$ satisfying the mild condition: $2omega(t)leq omega(Ht)+H$ for some $H>1$ and for all $tgeq0$, the space ${mathcal S}_omega$ in the sense of Bjorck is also nuclear.
We study the Coulomb branch of class $mathcal{S}_k$ $mathcal{N} = 1$ SCFTs by constructing and analyzing their spectral curves.
The experimental results on the ratios of branching fractions $mathcal{R}(D) = {cal B}(bar{B} to D tau^- bar{ u}_{tau})/{cal B}(bar{B} to D ell^- bar{ u}_{ell})$ and $mathcal{R}(D^*) = {cal B}(bar{B} to D^* tau^- bar{ u}_{tau})/{cal B}(bar{B} to D^* ell^- bar{ u}_{ell})$, where $ell$ denotes an electron or a muon, show a long-standing discrepancy with the Standard Model predictions, and might hint to a violation of lepton flavor universality. We report a new simultaneous measurement of $mathcal{R}(D)$ and $mathcal{R}(D^*)$, based on a data sample containing $772 times 10^6$ $Bbar{B}$ events recorded at the $Upsilon(4S)$ resonance with the Belle detector at the KEKB $e^+ e^-$ collider. In this analysis the tag-side $B$ meson is reconstructed in a semileptonic decay mode and the signal-side $tau$ is reconstructed in a purely leptonic decay. The measured values are $mathcal{R}(D)= 0.307 pm 0.037 pm 0.016$ and $mathcal{R}(D^*) = 0.283 pm 0.018 pm 0.014$, where the first uncertainties are statistical and the second are systematic. These results are in agreement with the Standard Model predictions within $0.2$, $1.1$ and $0.8$ standard deviations for $mathcal{R}(D)$, $mathcal{R}(D^*)$ and their combination, respectively. This work constitutes the most precise measurements of $mathcal{R}(D)$ and $mathcal{R}(D^*)$ performed to date as well as the first result for $mathcal{R}(D)$ based on a semileptonic tagging method.
We report a measurement of the ratios of branching fractions $mathcal{R}(D) = {cal B}(bar{B} to D tau^- bar{ u}_{tau})/{cal B}(bar{B} to D ell^- bar{ u}_{ell})$ and $mathcal{R}(D^{ast}) = {cal B}(bar{B} to D^* tau^- bar{ u}_{tau})/{cal B}(bar{B} to D^* ell^- bar{ u}_{ell})$, where $ell$ denotes an electron or a muon. The results are based on a data sample containing $772times10^6$ $Bbar{B}$ events recorded at the $Upsilon(4S)$ resonance with the Belle detector at the KEKB $e^+ e^-$ collider. The analysis utilizes a method where the tag-side $B$ meson is reconstructed in a semileptonic decay mode, and the signal-side $tau$ is reconstructed in a purely leptonic decay. The measured values are $mathcal{R}(D)= 0.307 pm 0.037 pm 0.016$ and $mathcal{R}(D^{ast})= 0.283 pm 0.018 pm 0.014$, where the first uncertainties are statistical and the second are systematic. These results are in agreement with the Standard Model predictions within $0.2$ and $1.1$ standard deviations, respectively, while their combination agrees with the Standard Model predictions within $1.2$ standard deviations.
We propose a generalization of S-folds to 4d $mathcal{N}=2$ theories. This construction is motivated by the classification of rank one 4d $mathcal{N}=2$ super-conformal field theories (SCFTs), which we reproduce from D3-branes probing a configuration of $mathcal{N}=2$ S-folds combined with 7-branes. The main advantage of this point of view is that realizes both Coulomb and Higgs branch flows and allows for a straight forward generalization to higher rank theories.