scholarly journals The Fréchet Schwartz Algebra of Uniformly Convergent Dirichlet Series

2018 ◽  
Vol 61 (4) ◽  
pp. 933-942 ◽  
Author(s):  
José Bonet
Keyword(s):  
Dirichlet Series ◽  
Half Plane ◽  
Composition Operators ◽  
Positive Real Part ◽  
Complex Numbers ◽  
Positive Real ◽  
Uniformly Convergent ◽  
Schwartz Algebra ◽  
Locally Convex Topology ◽  
Locally Convex

AbstractThe algebra of all Dirichlet series that are uniformly convergent in the half-plane of complex numbers with positive real part is investigated. When it is endowed with its natural locally convex topology, it is a non-nuclear Fréchet Schwartz space with basis. Moreover, it is a locally multiplicative algebra but not aQ-algebra. Composition operators on this space are also studied.

scholarly journals Dirichlet series with positive real part

1992 ◽  
Vol 46 (1) ◽  
pp. 159-166
Author(s):  
N. Samaris
Keyword(s):  
Dirichlet Series ◽  
Positive Real Part ◽  
Positive Real ◽  
Special Cases

We consider the sequence Λ = {0 < λ2 < λ2 < …}, for which λn → +∞. We denote by PD(Λ) the class of Dirichlet's series having the form F(s) = defined in the half plan Re s > 0 converging absolutely and Re F ≥ 0. If N0 = {0, 1,2, …} then the class PD(N0) coincides with the Caratheodory's class P. In this paper some classical results holding for the class P are generalised in any class PD(Λ). In special cases for the sequence Λ extreme problems are examined in the class PD(Λ).

scholarly journals On the Largest Disc Mapped by Sum of Convex and Starlike Functions

2013 ◽  
Vol 2013 ◽  
pp. 1-12 ◽  
Author(s):  
Rosihan M. Ali ◽  
Naveen Kumar Jain ◽  
V. Ravichandran
Keyword(s):  
Analytic Function ◽  
Half Plane ◽  
Unit Disc ◽  
Starlike Functions ◽  
Positive Real Part ◽  
Positive Real ◽  
Convex And Starlike Functions ◽  
The Right

For a normalized analytic functionfdefined on the unit disc𝔻, letϕ(f,f′,f′′;z)be a function of positive real part in𝔻,ψ(f,f′,f′′;z)need not have that property in𝔻, andχ=ϕ+ψ. For certain choices ofϕandψ, a sharp radius constantρis determined,0<ρ<1, so thatχ(ρz)/ρmaps𝔻onto a specified region in the right half-plane.

scholarly journals Toeplitz nonnegative realization of spectra via companion matrices

2019 ◽  
Vol 7 (1) ◽  
pp. 230-245
Author(s):  
Macarena Collao ◽  
Mario Salas ◽  
Ricardo L. Soto
Keyword(s):  
Eigenvalue Problem ◽  
Half Plane ◽  
Toeplitz Matrix ◽  
Toeplitz Matrices ◽  
Nonnegative Matrix ◽  
Inverse Eigenvalue Problem ◽  
Complex Numbers ◽  
Inverse Eigenvalue ◽  
Companion Matrices ◽  
Solution Matrix

Abstract The nonnegative inverse eigenvalue problem (NIEP) is the problem of finding conditions for the existence of an n × n entrywise nonnegative matrix A with prescribed spectrum Λ = {λ1, . . ., λn}. If the problem has a solution, we say that Λ is realizable and that A is a realizing matrix. In this paper we consider the NIEP for a Toeplitz realizing matrix A, and as far as we know, this is the first work which addresses the Toeplitz nonnegative realization of spectra. We show that nonnegative companion matrices are similar to nonnegative Toeplitz ones. We note that, as a consequence, a realizable list Λ= {λ1, . . ., λn} of complex numbers in the left-half plane, that is, with Re λi≤ 0, i = 2, . . ., n, is in particular realizable by a Toeplitz matrix. Moreover, we show how to construct symmetric nonnegative block Toeplitz matrices with prescribed spectrum and we explore the universal realizability of lists, which are realizable by this kind of matrices. We also propose a Matlab Toeplitz routine to compute a Toeplitz solution matrix.

scholarly journals Initial logarithmic coefficients for functions starlike with respect to symmetric points

2021 ◽  
Vol 27 (3) ◽  
Author(s):  
Paweł Zaprawa
Keyword(s):  
Exact Result ◽  
Positive Real Part ◽  
Additional Benefit ◽  
Extremal Functions ◽  
Positive Real ◽  
Logarithmic Coefficients ◽  
Symmetric Points

AbstractIn this paper, we obtain the bounds of the initial logarithmic coefficients for functions in the classes $${\mathcal {S}}_S^*$$ S S ∗ and $${\mathcal {K}}_S$$ K S of functions which are starlike with respect to symmetric points and convex with respect to symmetric points, respectively. In our research, we use a different approach than the usual one in which the coeffcients of f are expressed by the corresponding coeffcients of functions with positive real part. In what follows, we express the coeffcients of f in $${\mathcal {S}}_S^*$$ S S ∗ and $${\mathcal {K}}_S$$ K S by the corresponding coeffcients of Schwarz functions. In the proofs, we apply some inequalities for these functions obtained by Prokhorov and Szynal, by Carlson and by Efraimidis. This approach offers a additional benefit. In many cases, it is easily possible to predict the exact result and to select extremal functions. It is the case for $${\mathcal {S}}_S^*$$ S S ∗ and $${\mathcal {K}}_S$$ K S .

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