An algebraic group is called semi-reductive if it is a semi-direct product of a reductive subgroup and the unipotent radical.Such a semi-reductive algebraic group naturally arises and also plays a key role in the stud...An algebraic group is called semi-reductive if it is a semi-direct product of a reductive subgroup and the unipotent radical.Such a semi-reductive algebraic group naturally arises and also plays a key role in the study of modular representations of non-classical finite-dimensional simple Lie algebras in positive characteristic,and some other cases.Let G be a connected semi-reductive algebraic group over an algebraically closed field F and g=Lie(G).It turns out that G has many same properties as reductive groups,such as the Bruhat decomposition.In this note,we obtain an analogue of classical Chevalley restriction theorem for g,which says that the G-invariant ring F[g]~G is a polynomial ring if g satisfies a certain“positivity”condition suited for lots of cases we are interested in.As applications,we further investigate the nilpotent cones and resolutions of singularities for semi-reductive Lie algebras.展开更多
We consider the oscillatory integral operator Ta,mf(X) f(y)dy, where the function f is a Schwartz function.In this paper, the restriction theorem on Sn-1 for this operator is obtained. Moreover, we obtain a necess...We consider the oscillatory integral operator Ta,mf(X) f(y)dy, where the function f is a Schwartz function.In this paper, the restriction theorem on Sn-1 for this operator is obtained. Moreover, we obtain a necessary condition which ensures validity of the restriction theorem.展开更多
In this paper,we investigate the generalized Sublaplacian.We give the expression of the restriction operators explicitly.By introducing the generalized λ-twisted convolutions,we obtain the estimates of the restrictio...In this paper,we investigate the generalized Sublaplacian.We give the expression of the restriction operators explicitly.By introducing the generalized λ-twisted convolutions,we obtain the estimates of the restriction operators in the mixed L^P spaces.Finally,we get a restriction theorem associated with the generalized Sublaplacian.展开更多
This paper contains a detailed, self contained and more streamlined proof of the l^2 decoupling theorem for hypersurfaces from the paper of Bourgain and Demeter in 2015. The authors hope this will serve as a good warm...This paper contains a detailed, self contained and more streamlined proof of the l^2 decoupling theorem for hypersurfaces from the paper of Bourgain and Demeter in 2015. The authors hope this will serve as a good warm up for the readers interested in understanding the proof of Vinogradov's mean value theorem from the paper of Bourgain,Demeter and Guth in 2015.展开更多
This study investigates the restriction problem for the Riesz potentials of Hardy-Hausdorff spaces HH^1-γ(R^n)and Q-type spaces Qγ(R^n).By exploiting a geometric-measure theory generated by the indicatorlike functio...This study investigates the restriction problem for the Riesz potentials of Hardy-Hausdorff spaces HH^1-γ(R^n)and Q-type spaces Qγ(R^n).By exploiting a geometric-measure theory generated by the indicatorlike functions of compact sets,it is proved that the Riesz operator Iαcontinuously maps HH^1-γ(R^n)into the weak Morrey spaces L^q,λ/μ,*induced by a Radon measureμ,which obeys a geometric condition.展开更多
基金Supported by NSFC(Grant Nos.12071136,11671138,11771279,12101544)Shanghai Key Laboratory of PMMP(Grant No.13dz2260400)the Fundamental Research Funds of Yunnan Province(Grant No.2020J0375)。
文摘An algebraic group is called semi-reductive if it is a semi-direct product of a reductive subgroup and the unipotent radical.Such a semi-reductive algebraic group naturally arises and also plays a key role in the study of modular representations of non-classical finite-dimensional simple Lie algebras in positive characteristic,and some other cases.Let G be a connected semi-reductive algebraic group over an algebraically closed field F and g=Lie(G).It turns out that G has many same properties as reductive groups,such as the Bruhat decomposition.In this note,we obtain an analogue of classical Chevalley restriction theorem for g,which says that the G-invariant ring F[g]~G is a polynomial ring if g satisfies a certain“positivity”condition suited for lots of cases we are interested in.As applications,we further investigate the nilpotent cones and resolutions of singularities for semi-reductive Lie algebras.
文摘We consider the oscillatory integral operator Ta,mf(X) f(y)dy, where the function f is a Schwartz function.In this paper, the restriction theorem on Sn-1 for this operator is obtained. Moreover, we obtain a necessary condition which ensures validity of the restriction theorem.
文摘In this paper,we investigate the generalized Sublaplacian.We give the expression of the restriction operators explicitly.By introducing the generalized λ-twisted convolutions,we obtain the estimates of the restriction operators in the mixed L^P spaces.Finally,we get a restriction theorem associated with the generalized Sublaplacian.
基金supported by the NSF Grant DMS-1301619,the NSF Grant DMS-1161752
文摘This paper contains a detailed, self contained and more streamlined proof of the l^2 decoupling theorem for hypersurfaces from the paper of Bourgain and Demeter in 2015. The authors hope this will serve as a good warm up for the readers interested in understanding the proof of Vinogradov's mean value theorem from the paper of Bourgain,Demeter and Guth in 2015.
基金supported by National Natural Science Foundation of China(Grant Nos.11871293 and 11571217)Shandong Natural Science Foundation of China(Grant Nos.ZR2017JL008 and ZR2016AM05)University Science and Technology Projects of Shandong Province(Grant No.J15LI15)。
文摘This study investigates the restriction problem for the Riesz potentials of Hardy-Hausdorff spaces HH^1-γ(R^n)and Q-type spaces Qγ(R^n).By exploiting a geometric-measure theory generated by the indicatorlike functions of compact sets,it is proved that the Riesz operator Iαcontinuously maps HH^1-γ(R^n)into the weak Morrey spaces L^q,λ/μ,*induced by a Radon measureμ,which obeys a geometric condition.