527 research outputs found
Bohr's equivalence relation in the space of Besicovitch almost periodic functions
Based on Bohr's equivalence relation which was established for general
Dirichlet series, in this paper we introduce a new equivalence relation on the
space of almost periodic functions in the sense of Besicovitch,
, defined in terms of polynomial approximations. From
this, we show that in an important subspace , where Parseval's equality and Riesz-Fischer theorem
holds, its equivalence classes are sequentially compact and the family of
translates of a function belonging to this subspace is dense in its own class.Comment: Because of a mistake detected in one of the references, the
equivalence relation which is inspired by that of Bohr is revised to adapt
correctly the situation in the general case. arXiv admin note: text overlap
with arXiv:1801.0803
A generalization of Bohr's Equivalence Theorem
Based on a generalization of Bohr's equivalence relation for general
Dirichlet series, in this paper we study the sets of values taken by certain
classes of equivalent almost periodic functions in their strips of almost
periodicity. In fact, the main result of this paper consists of a result like
Bohr's equivalence theorem extended to the case of these functions.Comment: Because of a mistake detected in one of the references, the previous
version of this paper has been modified by the authors to restrict the scope
of its application to the case of existence of an integral basi
Multifaceted Mathematicians
This report attempts to provide an overview of some of the mathematicians who have combined their mathematical knowledge with other academic and non-academic specialities. The various examples given, many of them included in the well-known MacTutor History of Mathematics archive, corroborate the fact that although the idea of the typical polymath has receded with the passage of time, until the end of the Renaissance, most well-known mathematicians were also well-versed in a number of different sciences such as philosophy, astronomy, and physics. We also highlight other, less common combinations of knowledge, in famous mathematicians who were experts in other disciplines or activities of a totally disparate nature
Evolution and excitation conditions of outflows in high-mass star-forming regions
Theoretical models suggest that massive stars form via disk-mediated
accretion, with bipolar outflows playing a fundamental role. A recent study
toward massive molecular outflows has revealed a decrease of the SiO line
intensity as the object evolves. The present study aims at characterizing the
variation of the molecular outflow properties with time, and at studying the
SiO excitation conditions in outflows associated with massive YSOs. We used the
IRAM30m telescope to map 14 massive star-forming regions in the SiO(2-1),
SiO(5-4) and HCO+(1-0) outflow lines, and in several dense gas and hot core
tracers. Hi-GAL data was used to improve the spectral energy distributions and
the L/M ratio, which is believed to be a good indicator of the evolutionary
stage of the YSO. We detect SiO and HCO+ outflow emission in all the sources,
and bipolar structures in six of them. The outflow parameters are similar to
those found toward other massive YSOs. We find an increase of the HCO+ outflow
energetics as the object evolve, and a decrease of the SiO abundance with time,
from 10^(-8) to 10^(-9). The SiO(5-4) to (2-1) line ratio is found to be low at
the ambient gas velocity, and increases as we move to high velocities,
indicating that the excitation conditions of the SiO change with the velocity
of the gas (with larger densities and/or temperatures for the high-velocity gas
component). The properties of the SiO and HCO+ outflow emission suggest a
scenario in which SiO is largely enhanced in the first evolutionary stages,
probably due to strong shocks produced by the protostellar jet. As the object
evolves, the power of the jet would decrease and so does the SiO abundance.
During this process, however, the material surrounding the protostar would have
been been swept up by the jet, and the outflow activity, traced by entrained
molecular material (HCO+), would increase with time.Comment: 31 pages, 10 figures and 5 tables (plus 2 figures and 3 tables in the
appendix). Accepted for publication in A&A. [Abstract modified to fit the
arXiv requirements.
Molecules with a peptide link in protostellar shocks: a comprehensive study of L1157
Interstellar molecules with a peptide link -NH-C(=O)-, like formamide
(NHCHO), acetamide (NHCOCH) and isocyanic acid (HNCO) are
particularly interesting for their potential role in pre-biotic chemistry. We
have studied their emission in the protostellar shock regions L1157-B1 and
L1157-B2, with the IRAM 30m telescope, as part of the ASAI Large Program.
Analysis of the line profiles shows that the emission arises from the outflow
cavities associated with B1 and B2. Molecular abundance of
and are derived for
formamide and isocyanic acid, respectively, from a simple rotational diagram
analysis. Conversely, NHCOCH was not detected down to a relative
abundance of a few . B1 and B2 appear to be among the richest
Galactic sources of HNCO and NHCHO molecules. A tight linear correlation
between their abundances is observed, suggesting that the two species are
chemically related. Comparison with astrochemical models favours molecule
formation on ice grain mantles, with NHCHO generated from hydrogenation of
HNCO.Comment: 11 pages, 9 figures. Accepted for publication in MNRAS Main Journal.
Accepted 2014 August 19, in original form 2014 July
Cohen strongly p-summing holomorphic mappings on Banach spaces
Let and be complex Banach spaces, be an open subset of and
. We introduce and study the notion of a Cohen strongly
-summing holomorphic mapping from to , a holomorphic version of a
strongly -summing linear operator. For such mappings, we establish both
Pietsch domination/factorization theorems and analyse their linearizations from
(the canonical predual of ) and
their transpositions on . Concerning the space
formed by such mappings and endowed
with a natural norm , we show that it is a regular
Banach ideal of bounded holomorphic mappings generated by composition with the
ideal of strongly -summing linear operators. Moreover, we identify the space
with the
dual of the completion of tensor product space
endowed with the Chevet--Saphar norm
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