Abstract
We obtain a new extended description of the exceptional set in the asymptotic Borel-type relation in terms of the maximum of the integrand function for the Laplace–Stieltjes integrals. The obtained description of an exceptional set in the Borel-type relation leaves no room for improvement. In particular, we construct a corresponding measure, a function given by the Laplace–Stieltjes integral with respect to this measure, and a measurable set for which the opposite inequality to the Borel-type relation is fulfilled.
MSC:
30B50
1. Introduction
Analytic functions represented by Laplace–Stieltjes integrals [1,2] have interesting and important properties. If a function is represented by the Laplace–Stieltjes integral, then Vogl [3] has proven the uniform convergence on compacts of the Bruwier series constructed by the analytic function f and the uniform approximation of the generating function f by its Bruwier series in cones. Moreover, there are known characterizations [4] of conditionally positive definite functions on Euclidean spaces by certain Laplace–Stielties integrals. The relative growth of the Laplace–Stiltjes-type integrals and the growth properties of the maximum modulus related to the Laplace–Stiltjes-type integrals are investigated in [5,6]. The Laplace–Stieltjes transform is the simple sub-case of the Laplace–Stiltjes-type integral, but there are known inequalities concerning the abscissa of convergence, the abscissa of absolute convergence, and the abscissa of uniform convergence for the transform [7].
There are established lower and upper estimates for the Laplace–Stieltjes integrals [8] with an arbitrary abscissa of convergence. These were used to describe the relationship between the growth of the integral and the maximum of the integrand. Moreover, the lower estimates on a sequence for the maximum of the integrand of Laplace–Stieltjes integrals provide the possibility of deducing an analog of Whittaker’s theorem for a lacunary power series [9].
2. Preliminary Notations and Results
Let For we denote
Let be the support function of a measure in , which is a closed set such that and for every and .
We suppose that is a countably additive nonnegative measure on with unbounded , and is an arbitrary nonnegative -measurable function on By , we denote the -measure of a -measurable set
Under , we understand the class of the functions admitting such a representation
Let us denote by the class of nonnegative continuous functions on , such that as , by the subclass of non-decreasing functions , and by the subclass of of functions , such that
refers to the class-differentiable concave functions such that
The problem of finding asymptotic upper estimates for functions F belonging to the class by the asymptotic behavior of the supremum
was examined in [10,11] (for in [10]). The results contained only restrictions to the measure .
Theorem 6 from [10] states that if for some function and , the condition
is satisfied, then for each function it is possible to construct a set of finite Lebesgue measures, such that
as .
A similar multidimensional result for arbitrary was proven in [11,12]. The same problem for the entire Dirichlet series was studied in [13,14]. The growth cones for entire multiple Dirichlet series were first considered by Grechanyuk [15,16]. Since analytic functions are closely related with the harmonic functions, for this class of functions there are known growth estimates in a tangent cone at infinity [17].
Similar cones are base for the tubes B in from [18], for which abstract analytic functions are considered, which are Banach-space-valued or Hilber-space-valued functions. Moreover, the analytic functions can be given as the Fourier–Laplace transform applied to some vector-valued functions.
Throughout this article, each cone is a real cone with a vertex at the origin . For and a measure , we define
For and a measurable set , we denote
Theorem 1
([12]). Let K be an arbitrary cone such that its closure without origin is contained in the first p-dimensional octant, i.e., . If for a measure ν the condition
holds, then for each function there exists a set satisfies
and such that the relation
holds as and .
3. Auxiliary Statements: Growth Cones Associated with Functions of Form (1) and Measure
Let us denote by , that is, the support function of the set .
For a function F represented by the Laplace–Stieltjes integral in (1) and for , we define the following functions
Let us define the following cones in by the equalities
where is either a measure of or one of the functions F and .
The following statements are correct. Three of them will be used in the proofs of the main results. Another three lemmas characterize the relationship between the introduced notions of measure cone and growth cone.
Lemma 1
([11], Proposition 1). If F is the function of form (1), where , and ν is a countable-additive measure, the support of the measure is unbounded in p-dimensional positive real space (the first octant ), then
Lemma 2
([11], Proposition 2). For every
Lemma 3
([11], Proposition 3). If , then and .
Lemma 4
([11], Proposition 4). If , then for every
Lemma 5
([11], Proposition 5). The function is convex as a function of .
Lemma 6
([11], Proposition 5). For every cone K in p-dimensional real space whose vertex is the origin and whose closure without the vertex is a subset of the , i.e., , the asymptotic growth of the Laplace–Stieltjes integral is described as the following
Lemma 7.
If F is the function of form (1), where , and ν is a countable-additive measure having unbounded support in , then .
Proof.
On the contrary, we assume that there exists . Then, for arbitrary we obtain
where But, ; therefore,
hence, . This is a contradiction with the unboundedness of the support of the measure in . □
4. An Upper Estimate of Logarithhm of the Laplace–Stieltjes Integral in a Cone
We consider the measure that is the direct product of a probability measure P on the part of the unit sphere and the Lebesgue measure on the ray For a -measurable set we put
For the ball of radius , obviously
hence, in particular, in the case
For we define
and also
Denote . It is easy to see that from it follows that,
Lemma 8.
The set is a real positive cone.
Indeed, if , then for , , we have
thus
i.e.,
The following result is the main one in the paper. It claims that the -measure of the intersection of an exceptional set and any real cone is finite. The exceptional set is chosen so that relation (6) holds outside the set.
Theorem 2.
If , then there exists a set satisfying the condition
and such that relation (6) holds as for every and an arbitrary real cone K such that .
The next theorem immediately follows from Theorem 2. Condition (7) is not a condition, as denotations were introduced.
Theorem 3.
Proof of Theorem 3.
We put
and assume that K is an arbitrary real cone in with the vertex at the origin, such that . Let
Then, and for every
Thus,
We still need to apply the statement of Theorem 2. □
Proof of Theorem 2.
For , we define
Let . Consider the function
Without loss of generality, we suppose that
Similar to [11,12], for fixed , we examine the function By Lemma 5, the function g is convex on a real positive semi-axis. So, the right-hand derivative exists at each point and is a non-decreasing function. At the same time, the derivative exists almost everywhere. In the future, for every instance, instead of we will write .
Let us consider the probabilistic space with the probabilistic measure
and introduce the random variable on it. Let us denote by the mathematical expectation . It is easy to see that Similar to [10,11,12] by using Markov’s inequality with , we can prove that
Similarly to what was carried out in [12], for each fixed we will construct a function such that
for some .
Let , such that . We have
and . Thus, . Hence,
In addition,
For fixed , we denote
It is easy to see that , thus So, we can choose such that for all
Now, we choose a positive function increasing to as , such that the inverse function has the form
where is such that Remark, . So, , thus, by inequality (12)
and . Therefore, by relation (12), we obtain
One should observe that is non-decreasing. Then, it is possible to deduce such a lower estimate of the integral Thus, by Cauchy’s criterion, we have Therefore,
So, we obtain and (11).
Now, note that Lemma 6 implies
uniformly for , that is uniformly for .
For fixed , we denote
and
Then, for by definition of the set
It is easy to see that , and from (8), for sufficiently large . Therefore, from inequality (10) by definition of the set , we have
It means that the relation (6) is fulfilled as
Theorem 2 is completely proven. □
5. Existence of the Laplace–Stieltjes Integral with the Greater Growth than the Maximum of the Integrand Function
The necessity of condition (4) in Theorem 2 was proven for a one-dimensional case in [19]. It follows from Theorem 3 ([19]) that if is an arbitrary countably additive measure on , such that
then there exists a constant , a point and a function represented by the Laplace–Stieltjes integral such that
If the measure on is a direct product of the countably additive measures on , then the condition (4) in Theorem 2 is a necessary condition. This fact is contained in the following theorem.
Theorem 4.
Let , be the countably additive measures on , and a measure be such that . If and condition (4) is not satisfied, then there exist a constant , a measurable set E, and a function F from , represented by the Laplace–Stieltjes integral with respect to the measure μ, such that for all inequality (13) holds and
Proof.
In Theorem 2, from [12], it was proven if an improper integral in (4) is divergent and the function is bounded as then there exist a constant , a measurable set E, and a function , such that for all inequality (13) holds, where
We still now show that Let us make sure of this now. Indeed,
where
Theorem 4 is completely proved. □
6. Non-Improvability of the Description of an Exceptional Set in the Asymptotic Estimates of the Laplace–Stieltjes Integral
Many authors [20] obtained multidimensional analogs of known estimates in Wiman–Valiron’s theory without an explicit description of the exceptional sets. Filevych P. [21] examined such a problem concerning the analytic nature of the exceptional set: what is an impact of the Taylor coefficients of an entire function by the maximum modulus divided by the maximum of the real part for the function? It was discovered that the maximum modulus can have arbitrarily extreme growth with respect to the maximum of the real part or the Nevanlinna characteristic. Many relations in the theory of entire functions [22,23], meromorphic functions [24], and subharmonic functions [25] are valid for points which do not belong to some exceptional set of finite linear or logarithmic measures. Similarly, this fact remains true in the stochastic analysis for random entire functions [26]. Halburd and Korhonen proposed approaches [27] for a slight modification of certain inequalities to remove exceptional sets. For entire functions, there are known exceptional sets of other natures [28]. In particular, there are papers on the exceptional set of algebraic numbers, where a given transcendental entire function takes algebraic values. Such entire functions with rational Taylor coefficients exist for every subset of the field of algebraic numbers closed under complex conjugation [29,30,31].
Under the conditions of Theorem 2, the description (9) of an exceptional set E in the Borel-type relation (6) cannot be improved. To verify this, let us examine multiple Dirichlet series.
We consider the unit Dirac’s measure of a set G concentrated at the point and choose the measure , such that for each bounded set
We assume that is a fixed sequence, such that for and for all Then, is the class of entire Dirichlet series of the form
For and , we denote
Theorem 5.
Let be an arbitrary function. Then, there exist a countably additive measure ν on the σ-algebra of Borel sets satisfying condition (4), a function a constant , and a set such that:
and
for every measure , such that , .
Proof.
Let us consider a measure of the form (14). It is obvious that the condition (4) is equivalent to the condition
It is proved in [32] that for every there exists a sequence satisfying the condition (16), a constant , a function and a set , such that
where the set E has the form
and for
It leaves us to prove that the integral of h over the set E with respect to the measure is divergent, i.e., So, if we recall that for the set , then we obtain
where
This completes the proof of Theorem 5. □
Remark 1.
For an arbitrary set , we write
where for every . It is easy to see that
where is a probability measure on , and A is the area of , i.e., for . On the other hand, for example, in the simplest two-dimensional case we can choose a set such that and construct the set . Then, for the probabilistic measure P given by we obtain . However, it is obvious that .
Then Theorem 3 immediately implies the above-mentioned Theorem 1 ([12]), from Theorem 4, Theorem 2 in [12] follows, and Theorem 5 yields Corollary 1 in [12].
Theorem 2 also improves the relevant statements from [12,13].
7. Discussion
Given the obtained results, we can pose a natural conjecture.
Conjecture 1.
The following statement seems to be correct:
Question 1.
The example presented in Remark 1 leads to such a question:
Question 2.
Is there a function , given by the Laplace–Stieltjes integral, such that an exceptional set E in the Borel-type relation has the properties and .
We do not have an exhaustive answer to the question.
First and foremost, there are two differences that make the results of the paper more (“in-depth”) general:
- In previous results [11,13,32,33], the main estimate of the logarithm of the Laplace–Stieltjes integral is valid in the cones K such that . In the present paper, the estimate holds for the cones K, satisfying , where is a growth cone of the function i.e., it contains such points at which the lower limit of tends to positive infinity as Moreover, there is presented Lemma 7 claiming . In a general case, one has and, for example, if , the can be any angle (cone), such that Such examples were constructed in papers [15,16].
- Remark 1 claims that the description of the size of the exceptional set obtained by our predecessors [10,11,12] in follows from the description obtained in this paper, but we obtained the description in a much wider cone .
The main statements of the paper can be treated from the point of view that they provide an almost exhaustive answer to the question: what are the conditions by the measure in the Laplace–Stieltjes integral that provide the validity of the Borel-type relation on the growth cone outside a set E with ? Obviously, if the is the Lebesgue measure in , then the restrictions of the obtained theorems are satisfied.
Author Contributions
Conceptualization, O.S.; methodology, O.S.; validation, T.S.; formal analysis, D.Z.; investigation, D.Z.; writing—original draft preparation, T.S. and D.Z.; writing—review and editing, A.B.; supervision, O.S. All authors have read and agreed to the published version of the manuscript.
Funding
This research received no external funding.
Institutional Review Board Statement
Not applicable.
Informed Consent Statement
Not applicable.
Data Availability Statement
Data are contained within the article.
Conflicts of Interest
Dmytro Zikrach was employed by the Softserve, Inc. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
References
- Krainova, L.I. A Tauberian theorem for the Laplace-Stieltjes integrals. Funct. Anal. Appl. 1986, 20, 142–143. [Google Scholar] [CrossRef]
- Das, G.L. On the behavior of the function defined by a generalized Laplace-Stieltjes inregral. Proc. Koninklije Ned. Akad. Wetenschafen Ser. A-Math. Sci. 1980, 83, 119–123. [Google Scholar]
- Vogl, F. On the uniform approximation of a class of analytic functions by Bruwier series. J. Approx. Theory 2000, 107, 281–292. [Google Scholar] [CrossRef][Green Version]
- Guo, K.; Hu, S.; Sun, X. Conditionally positive-definite functions and Laplace-Stieltjes integrals. J. Approx. Theory 1993, 74, 249–265. [Google Scholar] [CrossRef][Green Version]
- Sheremeta, M. Relative Growth of Series in Systems of Functions and Laplace–Stieltjes-Type Integrals. Axioms 2021, 10, 43. [Google Scholar] [CrossRef]
- Kong, Y.; Yang, Y. On the growth properties of the Laplace–Stieltjes transform. Complex Var. Elliptic Equ. 2013, 59, 553–563. [Google Scholar] [CrossRef]
- Xu, H.Y.; Xuan, Z.X. Some inequalities on the convergent abscissas of Laplace-Stieltjes transforms. J. Math. Inequalities 2023, 17, 163–164. [Google Scholar] [CrossRef]
- Dobushovs’kyi, M.S.; Sheremeta, M.M. Estimation of the Laplace-Stieltjes Integrals. Ukr. Math. J. 2017, 68, 1694–1714. [Google Scholar] [CrossRef]
- Dobushovskyy, M.S.; Sheremeta, M.M. Analogues of Whittaker’s theorem for Laplace-Stieltles integrals. Carpathian Math. Publ. 2016, 8, 239–250. [Google Scholar] [CrossRef]
- Skaskiv, O.B. On certain relations between the maximum modulus and the maximal term of an entire Dirichlet series. Math. Notes 1999, 66, 223–232. [Google Scholar] [CrossRef]
- Skaskiv, O.B.; Trakalo, O.M. Asymptotic estimates for Laplace integrals. Mat. Stud. 2002, 18, 125–146. (In Ukrainian) [Google Scholar]
- Skaskiv, O.B.; Zikrach, D.Y. On the best possible description of an exceptional set in asymptotic estimates for Laplace–Stieltjes integrals. Mat. Stud. 2011, 35, 131–141. [Google Scholar]
- Skaskiv, O.B.; Zikrach, D.Y. The best possible description of exceptional set in Borel’s relation for multiple Dirichlet series. Mat. Stud. 2008, 30, 189–194. [Google Scholar]
- Sheremeta, M.N. Behavior of the maximum of the absolute value of an entire Dirichlet series outside an exceptional set. Math. Notes 1995, 57, 198–207. [Google Scholar] [CrossRef]
- Grechanyuk, N.I. On the cone of growth of integral double Dirichlet series. Growth cone of entire double Dirichlet series. Sov. Math. (Iz. Vuz.) 1990, 34, 19–26. [Google Scholar]
- Grechanyuk, N.I. Growth cone of entire double Dirichlet series. Russ. Math. (Iz. Vuz.) 1992, 36, 11–15. [Google Scholar]
- Huang, X.-T. Harmonic functions with polynomial growth on manifolds with nonnegative Ricci curvature. Calc. Var. Partial Differ. Equ. 2023, 62, 111. [Google Scholar] [CrossRef]
- Carmichael, R.D. Generalized Vector-Valued Hardy Functions. Axioms 2022, 11, 39. [Google Scholar] [CrossRef]
- Skaskiv, O.B.; Trakalo, O.M. On the stability of the maximum term of the entire Dirichlet series. Ukr. Math. J. 2005, 57, 686–693. [Google Scholar] [CrossRef]
- Fenton, P.C. A Note on the Wiman-Valiron Method. Proc. Edinb. Math. Soc. 1994, 37, 53–55. [Google Scholar] [CrossRef]
- Filevich, P.V. Asymptotic relations between maximums of absolute values and maximums of real parts of entire functions. Math. Notes 2004, 75, 410–417. [Google Scholar] [CrossRef]
- Huang, J.; Marques, D.; Mereb, M. Algebraic Values of Transcendental Functions at Algebraic Points. Bull. Aust. Math. Soc. 2010, 82, 322–327. [Google Scholar] [CrossRef]
- Zabolotskyj, M.V.; Mostova, M.R. Asymptotic behavior of the logarithmic derivative of entire functions of zero order. Carpathian Math. Publ. 2014, 6, 237–241. [Google Scholar] [CrossRef][Green Version]
- Korhonen, R.; Tohge, K.; Zhang, Y.; Zheng, J. A lemma on the difference quotients. Ann. Acad. Sci. Fenn.-Math. 2020, 45, 479–491. [Google Scholar] [CrossRef]
- Khabibullin, B.N. The Logarithm of the Modulus of an Entire Function as a Minorant for a Subharmonic Function outside a Small Exceptional Set. Azerbaijan J. Math. 2021, 11, 48–59. [Google Scholar]
- Nishry, A. The hole probability for Gaussian entire functions. Isr. J. Math. 2011, 186, 197–220. [Google Scholar] [CrossRef][Green Version]
- Halburd, R.G.; Korhonen, R.J. Nondecreasing functions, exceptional sets and generalized Borel lemmas. J. Aust. Math. Soc. 2010, 88, 353–361. [Google Scholar] [CrossRef]
- Bustinduy, A. Exceptional values of entire functions of finite order in one of the variables. Bull. Sci. Math. 2023, 189, 103344. [Google Scholar] [CrossRef]
- Marques, D.; Ramirez, J. On exceptional sets: The solution of a porblem posed by K. Mahler. Bull. Aust. Math. Soc. 2016, 94, 15–19. [Google Scholar] [CrossRef]
- Marques, D.; Schleishitz, J. On a problem posed by Mahler. J. Aust. Math. Soc. 2016, 100, 86–107. [Google Scholar] [CrossRef]
- Alves, D.; Lelis, J.; Marques, D.; Trojovský, P. On the exceptional set of transcendental entire functions in several variables. Bull. Aust. Math. Soc. 2024, 110, 64–71. [Google Scholar] [CrossRef]
- Zikrach, D.Y.; Skaskiv, O.B. On the description of an exceptional set in Borel’s relation for multiple Dirichlet series with upper restriction on the growth. Mat. Stud. 2009, 32, 139–147. (In Ukrainian) [Google Scholar]
- Skaskiv, O.B.; Oryshchyn, O.H. Generalization of Borel’s theorem for the multiple Dirichlet series. Mat. Stud. 1997, 8, 43–52. (In Ukrainian) [Google Scholar]
Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content. |
© 2025 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).