{"title":"ON THE MILNOR FIBRATION OF CERTAIN NEWTON DEGENERATE FUNCTIONS","authors":"C. Eyral, M. Oka","doi":"10.1017/nmj.2022.37","DOIUrl":"https://doi.org/10.1017/nmj.2022.37","url":null,"abstract":"Abstract It is well known that the diffeomorphism type of the Milnor fibration of a (Newton) nondegenerate polynomial function f is uniquely determined by the Newton boundary of f. In the present paper, we generalize this result to certain degenerate functions, namely we show that the diffeomorphism type of the Milnor fibration of a (possibly degenerate) polynomial function of the form \u0000$f=f^1cdots f^{k_0}$\u0000 is uniquely determined by the Newton boundaries of \u0000$f^1,ldots , f^{k_0}$\u0000 if \u0000${f^{k_1}=cdots =f^{k_m}=0}$\u0000 is a nondegenerate complete intersection variety for any \u0000$k_1,ldots ,k_min {1,ldots , k_0}$\u0000 .","PeriodicalId":49785,"journal":{"name":"Nagoya Mathematical Journal","volume":null,"pages":null},"PeriodicalIF":0.8,"publicationDate":"2021-08-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45906677","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"LIE ALGEBRA MODULES WHICH ARE LOCALLY FINITE AND WITH FINITE MULTIPLICITIES OVER THE SEMISIMPLE PART","authors":"V. Mazorchuk, Rafael Mrðen","doi":"10.1017/nmj.2021.8","DOIUrl":"https://doi.org/10.1017/nmj.2021.8","url":null,"abstract":"Abstract For a finite-dimensional Lie algebra \u0000$mathfrak {L}$\u0000 over \u0000$mathbb {C}$\u0000 with a fixed Levi decomposition \u0000$mathfrak {L} = mathfrak {g} ltimes mathfrak {r}$\u0000 , where \u0000$mathfrak {g}$\u0000 is semisimple, we investigate \u0000$mathfrak {L}$\u0000 -modules which decompose, as \u0000$mathfrak {g}$\u0000 -modules, into a direct sum of simple finite-dimensional \u0000$mathfrak {g}$\u0000 -modules with finite multiplicities. We call such modules \u0000$mathfrak {g}$\u0000 -Harish-Chandra modules. We give a complete classification of simple \u0000$mathfrak {g}$\u0000 -Harish-Chandra modules for the Takiff Lie algebra associated to \u0000$mathfrak {g} = mathfrak {sl}_2$\u0000 , and for the Schrödinger Lie algebra, and obtain some partial results in other cases. An adapted version of Enright’s and Arkhipov’s completion functors plays a crucial role in our arguments. Moreover, we calculate the first extension groups of infinite-dimensional simple \u0000$mathfrak {g}$\u0000 -Harish-Chandra modules and their annihilators in the universal enveloping algebra, for the Takiff \u0000$mathfrak {sl}_2$\u0000 and the Schrödinger Lie algebra. In the general case, we give a sufficient condition for the existence of infinite-dimensional simple \u0000$mathfrak {g}$\u0000 -Harish-Chandra modules.","PeriodicalId":49785,"journal":{"name":"Nagoya Mathematical Journal","volume":null,"pages":null},"PeriodicalIF":0.8,"publicationDate":"2021-08-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87837443","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"IWASAWA THEORY FOR p-TORSION CLASS GROUP SCHEMES IN CHARACTERISTIC p","authors":"J. Booher, Bryden Cais","doi":"10.1017/nmj.2022.30","DOIUrl":"https://doi.org/10.1017/nmj.2022.30","url":null,"abstract":"Abstract We investigate a novel geometric Iwasawa theory for \u0000${mathbf Z}_p$\u0000 -extensions of function fields over a perfect field k of characteristic \u0000$p>0$\u0000 by replacing the usual study of p-torsion in class groups with the study of p-torsion class group schemes. That is, if \u0000$cdots to X_2 to X_1 to X_0$\u0000 is the tower of curves over k associated with a \u0000${mathbf Z}_p$\u0000 -extension of function fields totally ramified over a finite nonempty set of places, we investigate the growth of the p-torsion group scheme in the Jacobian of \u0000$X_n$\u0000 as \u0000$nrightarrow infty $\u0000 . By Dieudonné theory, this amounts to studying the first de Rham cohomology groups of \u0000$X_n$\u0000 equipped with natural actions of Frobenius and of the Cartier operator V. We formulate and test a number of conjectures which predict striking regularity in the \u0000$k[V]$\u0000 -module structure of the space \u0000$M_n:=H^0(X_n, Omega ^1_{X_n/k})$\u0000 of global regular differential forms as \u0000$nrightarrow infty .$\u0000 For example, for each tower in a basic class of \u0000${mathbf Z}_p$\u0000 -towers, we conjecture that the dimension of the kernel of \u0000$V^r$\u0000 on \u0000$M_n$\u0000 is given by \u0000$a_r p^{2n} + lambda _r n + c_r(n)$\u0000 for all n sufficiently large, where \u0000$a_r, lambda _r$\u0000 are rational constants and \u0000$c_r : {mathbf Z}/m_r {mathbf Z} to {mathbf Q}$\u0000 is a periodic function, depending on r and the tower. To provide evidence for these conjectures, we collect extensive experimental data based on new and more efficient algorithms for working with differentials on \u0000${mathbf Z}_p$\u0000 -towers of curves, and we prove our conjectures in the case \u0000$p=2$\u0000 and \u0000$r=1$\u0000 .","PeriodicalId":49785,"journal":{"name":"Nagoya Mathematical Journal","volume":null,"pages":null},"PeriodicalIF":0.8,"publicationDate":"2021-07-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43187510","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"POSITIVELY CURVED FINSLER METRICS ON VECTOR BUNDLES","authors":"Kuang-Ru Wu","doi":"10.1017/nmj.2022.2","DOIUrl":"https://doi.org/10.1017/nmj.2022.2","url":null,"abstract":"Abstract We construct a convex and strongly pseudoconvex Kobayashi positive Finsler metric on a vector bundle E under the assumption that the symmetric power of the dual \u0000$S^kE^*$\u0000 has a Griffiths negative \u0000$L^2$\u0000 -metric for some k. The proof relies on the negativity of direct image bundles and the Minkowski inequality for norms. As a corollary, we show that given a strongly pseudoconvex Kobayashi positive Finsler metric, one can upgrade to a convex Finsler metric with the same property. We also give an extremal characterization of Kobayashi curvature for Finsler metrics.","PeriodicalId":49785,"journal":{"name":"Nagoya Mathematical Journal","volume":null,"pages":null},"PeriodicalIF":0.8,"publicationDate":"2021-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47001755","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"POWER SERIES PROOFS FOR LOCAL STABILITIES OF KÄHLER AND BALANCED STRUCTURES WITH MILD \u0000$partial overline {partial }$\u0000 -LEMMA","authors":"S. Rao, Xueyuan Wan, Quanting Zhao","doi":"10.1017/nmj.2021.4","DOIUrl":"https://doi.org/10.1017/nmj.2021.4","url":null,"abstract":"Abstract By use of a natural map introduced recently by the first and third authors from the space of pure-type complex differential forms on a complex manifold to the corresponding one on the small differentiable deformation of this manifold, we will give a power series proof for Kodaira–Spencer’s local stability theorem of Kähler structures. We also obtain two new local stability theorems, one of balanced structures on an n-dimensional balanced manifold with the \u0000$(n-1,n)$\u0000 th mild \u0000$partial overline {partial }$\u0000 -lemma by power series method and the other one on p-Kähler structures with the deformation invariance of \u0000$(p,p)$\u0000 -Bott–Chern numbers.","PeriodicalId":49785,"journal":{"name":"Nagoya Mathematical Journal","volume":null,"pages":null},"PeriodicalIF":0.8,"publicationDate":"2021-06-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1017/nmj.2021.4","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48068824","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}