arXiv subjects

Youhei Morita

Publications and source records attributed to Youhei Morita.

5 recordsLinked to original sources

arXiv2026

Complete flags on flat vector bundles in positive characteristic

Let $X$ be a connected, smooth, and projective curve of genus $g$ over an algebraically closed field of characteristic $p >0$. This paper investigates a characteristic-$p$ analogue of a well-known fact concerning flat vector bundles in characteristic $0$. That is to say, we prove that the inequality $g \leq 1$ holds if and only if any flat vector bundle on $X$ admits a complete flag. We also explore a generalization of this result in a broader setting.

math.AG↗

arXiv2026

The modulo eight behavior of common factors of two hypergeometric polynomials arising from a genus three heperelliptic family

We study a one-parameter family of smooth projective genus-three hyperelliptic curves over algebraically closed fields of odd characteristic, with the parameter different from zero and one. We translate superspeciality into the simultaneous vanishing of two truncated hypergeometric polynomials arising from the Cartier operator. For their monic greatest common divisor, we prove squarefreeness and show that every irreducible factor has degree at most two. We then determine its behavior according to the characteristic modulo eight: in one residue class every nonconstant irreducible factor is quadratic; in two residue classes the greatest common divisor is trivial; and in the remaining residue class a distinguished linear factor always occurs.

math.AG↗

arXiv2026

Genus formulas for dormant modular curves and asymptotic behavior of their function fields

Towers of algebraic function fields over finite fields play a fundamental role in arithmetic geometry and coding theory. Classical examples arising from modular and Drinfeld modular curves exhibit asymptotically good behavior. In this paper, we introduce an analogous construction derived from the moduli spaces of higher-level dormant $\mathrm{PGL}_2$-opers of prescribed radii on $4$-pointed stable curves of genus $0$. These spaces, which we refer to as dormant modular curves, form projective systems under level reduction. Building on previous results in the moduli theory of dormant opers, we establish an explicit formula for computing the genera of these curves. This formula allows us to study the asymptotic behavior of the corresponding towers of function fields and to compare them with the classical modular and Drinfeld modular cases.

math.AG↗

arXiv2003

A data Grid testbed environment in Gigabit WAN with HPSS

For data analysis of large-scale experiments such as LHC Atlas and other Japanese high energy and nuclear physics projects, we have constructed a Grid test bed at ICEPP and KEK. These institutes are connected to national scientific gigabit network backbone called SuperSINET. In our test bed, we have installed NorduGrid middleware based on Globus, and connected 120TB HPSS at KEK as a large scale data store. Atlas simulation data at ICEPP has been transferred and accessed using SuperSINET. We have tested various performances and characteristics of HPSS through this high speed WAN. The measurement includes comparison between computing and storage resources are tightly coupled with low latency LAN and long distant WAN.

cs.DC↗

arXiv2003

Worldwide Fast File Replication on Grid Datafarm

The Grid Datafarm architecture is designed for global petascale data-intensive computing. It provides a global parallel filesystem with online petascale storage, scalable I/O bandwidth, and scalable parallel processing, and it can exploit local I/O in a grid of clusters with tens of thousands of nodes. One of features is that it manages file replicas in filesystem metadata for fault tolerance and load balancing. This paper discusses and evaluates several techniques to support long-distance fast file replication. The Grid Datafarm manages a ranked group of files as a Gfarm file, each file, called a Gfarm file fragment, being stored on a filesystem node, or replicated on several filesystem nodes. Each Gfarm file fragment is replicated independently and in parallel using rate-controlled HighSpeed TCP with network striping. On a US-Japan testbed with 10,000 km distance, we achieve 419 Mbps using 2 nodes on each side, and 741 Mbps using 4 nodes out of 893 Mbps with two transpacific networks.

cs.PF↗