53 research outputs found
S-regular functions which preserve a complex slice
We study global properties of quaternionic slice regular functions (also
called s-regular) defined on symmetric slice domains. In particular, thanks to
new techniques and points of view, we can characterize the property of being
one-slice preserving in terms of the projectivization of the vectorial part of
the function. We also define a "Hermitian" product on slice regular functions
which gives us the possibility to express the -product of two s-regular
functions in terms of the scalar product of suitable functions constructed
starting from and . Afterwards we are able to determine, under different
assumptions, when the sum, the -product and the -conjugation of two slice
regular functions preserve a complex slice. We also study when the -power of
a slice regular function has this property or when it preserves all complex
slices. To obtain these results we prove two factorization theorems: in the
first one, we are able to split a slice regular function into the product of
two functions: one keeping track of the zeroes and the other which is
never-vanishing; in the other one we give necessary and sufficient conditions
for a slice regular function (which preserves all complex slices) to be the
symmetrized of a suitable slice regular one.Comment: 23 pages, to appear in Annali di Matematica Pura e Applicat
-exponential of slice-regular functions
According to [5] we define the -exponential of a slice-regular function,
which can be seen as a generalization of the complex exponential to
quaternions. Explicit formulas for are provided, also in terms of
suitable sine and cosine functions. We completely classify under which
conditions the -exponential of a function is either slice-preserving or
-preserving for some and show that
is never-vanishing. Sharp necessary and sufficient conditions are given in
order that , finding an exceptional and
unexpected case in which equality holds even if and do not commute. We
also discuss the existence of a square root of a slice-preserving regular
function, characterizing slice-preserving functions (defined on the
circularization of simply connected domains) which admit square roots. Square
roots of this kind of functions are used to provide a further formula for
. A number of examples is given throughout the paper.Comment: 15 pages; to appear in Proceedings of the American Mathematical
Societ
Applications of the Sylvester operator in the space of slice semi-regular functions
AbstractIn this paper we apply the results obtained in [3] to establish some outcomes of the study of the behaviour of a class of linear operators, which include the Sylvester ones, acting on slice semi-regular functions. We first present a detailed study of the kernel of the linear operator ℒf,g (when not trivial), showing that it has dimension 2 if exactly one between f and g is a zero divisor, and it has dimension 3 if both f and g are zero divisors. Afterwards, we deepen the analysis of the behaviour of the -product, giving a complete classification of the cases when the functions fv, gv and fvgv are linearly dependent and obtaining, as a by-product, a necessary and sufficient condition on the functions f and g in order their *-product is slice-preserving. At last, we give an Embry-type result which classifies the functions f and g such that for any function h commuting with f + g and f * g, we have that h commutes with f and g, too
-Logarithm for Slice Regular Functions
In this paper, we study the (possible) solutions of the equation
, where is a slice regular never vanishing function on a
circular domain of the quaternions and is the natural
generalization of the usual exponential to the algebra of slice regular
functions. Any function which satisfies is called a
-logarithm of . We provide necessary and sufficient conditions, expressed
in terms of the zero set of the ``vector'' part of , for the
existence of a -logarithm of , under a natural topological condition on
the domain . By the way, we prove an existence result if has no
non-real isolated zeroes; we are also able to give a comprehensive approach to
deal with more general cases. We are thus able to obtain an existence result
when the non-real isolated zeroes of are finite, the domain is either
the unit ball, or , or and a further condition on the
``real part'' of is satisfied (see Theorem 6.19 for a precise
statement). We also find some unexpected uniqueness results, again related to
the zero set of , in sharp contrast with the complex case. A number of
examples are given throughout the paper in order to show the sharpness of the
required conditions.Comment: 27 pages, 4 figure
A STEM Literacy Program for Students in Secondary-Tertiary Transition to Reduce the Gender Gap: a Focus on the Students' Perception
This study concerns the design and implementation of a STEM literacy program for 11th to 13th-grade high achieving students, mainly females. The program, funded by the Italian Ministry of Equal Opportunities, aims at reducing the gender gap in the STEM disciplines and at orienting students towards university studies. We carried out a qualitative analysis of the students’ perception in terms of (1) a-priori expectations about the STEM literacy program and (2) a-posteriori thoughts and reflections about the attended course. Our analysis shows that students aspiring to participate had strong motivations with respect to the program; moreover, most students who participated in the program displayed satisfaction and an increase of awareness about their learning. We put a specific focus on the mathematical sessions of the curriculum, involving students as designers of educational resources. Some differences between male and female students arose for what concerns the perception of the program and the awareness of the impact of the STEM literacy program on their own learning
INCB84344-201: Ponatinib and steroids in frontline therapy for unfit patients with Ph+ acute lymphoblastic leukemia
Tyrosine kinase inhibitors have improved survival for patients with Philadelphia chromosome-positive (Ph+) acute lymphoblastic leukemia (ALL). However, prognosis for old or unfit patients remains poor. In the INCB84344-201 (formerly GIMEMA LAL 1811) prospective, multicenter, phase 2 trial, we tested the efficacy and safety of ponatinib plus prednisone in newly diagnosed patients with Ph+ ALL 6560 years, or unfit for intensive chemotherapy and stem cell transplantation. Forty-four patients received oral ponatinib 45 mg/d for 48 weeks (core phase), with prednisone tapered to 60 mg/m2/d from days-14-29. Prophylactic intrathecal chemotherapy was administered monthly. Median age was 66.5 years (range, 26-85). The primary endpoint (complete hematologic response [CHR] at 24 weeks) was reached in 38/44 patients (86.4%); complete molecular response (CMR) in 18/44 patients (40.9%) at 24 weeks. 61.4% of patients completed the core phase. As of 24 April 2020, median event-free survival was 14.31 months (95% CI 9.30-22.31). Median overall survival and duration of CHR were not reached; median duration of CMR was 11.6 months. Most common treatment-emergent adverse events (TEAEs) were rash (36.4%), asthenia (22.7%), alanine transaminase increase (15.9%), erythema (15.9%), and \u3b3-glutamyltransferase increase (15.9%). Cardiac and vascular TEAEs occurred in 29.5% (grade 653, 18.2%) and 27.3% (grade 653, 15.9%), respectively. Dose reductions, interruptions, and discontinuations due to TEAEs occurred in 43.2%, 43.2%, and 27.3% of patients, respectively; 5 patients had fatal TEAEs. Ponatinib and prednisone showed efficacy in unfit patients with Ph+ ALL; however, a lower ponatinib dose may be more appropriate in this population. This trial was registered at www.clinicaltrials.gov as #NCT01641107
One parameter groups of volume preserving automorphisms of
Si esaminano i gruppi ad un parametro nel gruppo degli automorfismi
polinomiali di C e nel gruppo degli shears, provando che sono
coniugati a gruppi a un parametro nel gruppo degli automorfismi affini
di C o nel gruppo degli automorfismi elementari; da ciò si
deducono risultati sul comportamento asintotico del gruppo ad un parametro,
sui suoi punti periodici e sui suoi punti fissi.In this work we study the one-parameter groups in the group of all
polynomial automorphisms of C and in the group of all shears.
We prove that any such one-parameter group is conjugated to a one-parameter
group contained either in the group of all affine automorphisms of
C or in the group of elementary automorphisms. This implies
some results on the asymptotic behaviour of the one-parameter group,
on its periodic points and on its fixed points
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