611 research outputs found
Hilbert-Kunz multiplicity of three-dimensional local rings
In this paper, we investigate a lower bound (say ) on
Hilbert-Kunz multiplicities for non-regular unmixed local rings of Krull
dimension with characteristic . Especially, we focus three-dimensional
local rings. In fact, as a main result, we will prove that
and that a three-dimensional complete local ring of Hilbert-Kunz multiplicity
4/3 is isomorphic to the non-degnerate quadric hyperplanes
under mild conditions. Furthermore, we pose a
generalization of the main theorem to the case of as a
conjecture, and show that it is also true in case of using the
similar method as in the proof of the main theorem.Comment: about 21 pages, LaTe
Minimal Hilbert-Kunz multiplicity
In this paper, we ask the following question: what is the minimal value of
the difference for ideals with
? In order to answer to this question, we define the notion of
minimal Hilbert-Kunz multiplicity for strongly F-regular rings. Moreover, we
calculate this invariant for quotient singularities and for the coordinate ring
of the Segre embedding: ,
respectively.Comment: about 22 pages, AMS-Te
Good ideals and -ideals in two-dimensional normal singularities
In this paper, we introduce the notion of -ideals and -cycles,
which inherits nice properties of integrally closed ideals on rational
singularities. As an application, we prove an existence of good ideals for
two-dimensional Gorenstein normal local rings. Moreover, we classify all Ulrich
ideals for two-dimensional simple elliptic singularities with small degree.Comment: 21 pages. The proof of Proposition 5.6 of the first version has been
revise
Rees algebras and -ideals in a two-dimensional normal local domain
The authors introduced the notion of -ideals for two-dimensional
excellent normal local domain over an algebraicaly closed field in terms of
resolution of singularities. In this note, we give several ring-theoretic
characterization of -ideals. For instance, an -primary ideal is a -ideal if and only if the Rees alegbra is a
Cohen-Macaulay normal domain.Comment: 10 page
Normal reduction numbers for normal surface singularities with application to elliptic singularities of Brieskorn type
In this paper, we give a formula for normal reduction number of an integrally
closed -primary ideal of a -dimensional normal local ring
in terms of the geometric genus of . Also we
compute the normal reduction number of the maximal ideal of Brieskorn
hypersurfaces. As an application, we give a short proof of a classification of
Brieskorn hypersurfaces having elliptic singularities.Comment: 14 page
A characterization of two-dimensional rational singularities via Core of ideals
The notion of -ideals for normal surface singularities has been proved
to be very useful. On the other hand, the core of ideals has been proved to be
very important concept and also very mysterious one. However, the computation
of the core of an ideal seems to be given only for very special cases. In this
paper, we will give an explicit description of the core of -ideals of
normal surface singularities. As a consequence, we give a characterization of
rational singularities using the inclusion of the core of integrally closed
ideals.Comment: 16 pages; various corrections and improvements. To appear in Journal
of Algebr
The strong Rees property of powers of the maximal ideal and Takahashi-Dao's question
In this paper, we introduce the notion of the strong Rees property (SRP) for
-primary ideals of a Noetherian local ring and prove that any
power of the maximal ideal has its property if the associated
graded ring of satisfies . As its
application, we characterize two-dimensional excellent normal local domains so
that is a -ideal. Finally we ask what
-primary ideals have SRP and state a conjecture which
characterizes the case when are the only ideals which have
SRP
Ulrich ideals and modules over two-dimensional rational singularities
The main aim of this paper is to classify Ulrich ideals and Ulrich modules
over two-dimensional Gorenstein rational singularities (rational double points)
from a geometric point of view. To achieve this purpose, we introduce the
notion of (weakly) special Cohen-Macaulay modules with respect to ideals, and
study the relationship between those modules and Ulrich modules with respect to
good ideals.Comment: 30 page
Irregular Oscillatory-Patterns in the Early-Time Region of Coherent Phonon Generation in Silicon
Coherent phonon (CP) generation in an undoped Si crystal is theoretically
investigated to shed light on unexplored quantum-mechanical effects in the
early-time region immediately after the irradiation of ultrashort laser pulse.
One examines time signals attributed to an induced charge density of an ionic
core, placing the focus on the effects of the Rabi frequency on
the signals; this frequency corresponds to the peak electric-field of the
pulse. It is found that at specific 's where the energy of
plasmon caused by photoexcited carriers coincides with the longitudinal-optical
phonon energy, the energetically {\it resonant } interaction between these two
modes leads to striking anticrossings, revealing irregular oscillations with
anomalously enhanced amplitudes in the observed time signals. Also, the
oscillatory pattern is subject to the Rabi flopping of the excited carrier
density that is controlled by . These findings show that the
early-time region is enriched with quantum-mechanical effects inherent in the
CP generation, though experimental signals are more or less masked by the
so-called coherent artifact due to nonlinear optical effects.Comment: 5 pages, 4 figure
Polaronic-Quasiparticle Picture for Generation Dynamics of Coherent Phonons in Semiconductors: Transient and Non-Linear Fano Resonance
We examine generation dynamics of coherent phonons (CPs) in both of polar and
non-polar semiconductors -- such as GaAs and Si -- based on a
polaronic-quasiparticle (PQ) model. In the model concerned, the PQ operator is
composed of two kinds of operators. One is a quasiboson operator -- defined as
a linear combination of a set of pairs of electron operators -- and the other
is a longitudinal optical (LO) phonon operator. The problem of transient and
non-linear Fano resonance (FR) is tackled in particular; the vestige of this
quantum interference effect was observed exclusively in lightly -doped Si
immediately after carriers were excited by an ultrashort pulse-laser [M. Hase
et. al., Nature 426, 51 (2003)], though not observed yet in GaAs. It is shown
that the phonon energy state is embedded in a continuum state formed by a set
of adiabatic eigenstates of the quasiboson. This result implies the possibility
of manifestation of the transient FR in the present optically-non-linear
system.Comment: 28 pages, 13 figure
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