arXiv subjects

Dibyendu De

Publications and source records attributed to Dibyendu De.

10 recordsLinked to original sources

arXiv2024

A Study on Filter Version of Strongly Central Sets

Using the notions of Topological dynamics, H. Furstenberg defined central sets and proved the Central Sets Theorem. Later V. Bergelson and N. Hindman characterized central sets in terms of algebra of the Stone-Čech compactification of discrete semigroup. They found that central sets are the members of the minimal idempotents of \b{eta}S, the Stone-Čech compactification of a semigroup (S, .). Hindman and leader introduced the notion of Central set near zero algebraically. Later dynamical and combinatorial characterization have also been established. For any given filter F in S a set A is said to be a F- central set if it is a member of a minimal idempotent of a closed subsemigroup of \b{eta}S, generated by the filter F. In a recent article Bergelson, Hindman and Strauss introduced strongly central and very strongly central sets in [BHS]. They also dynamically characterized the sets in the same paper. In the present article we will characterize the strongly F- central sets dynamically and combinatorially. Here we introduce the filter version of strongly central sets and very strongly central sets. We also provide dynamical and combinatorial characterization of such sets.

math.CO↗

arXiv2024

Non commutative multidimensional stronger Central Sets Theorem

Hindman's theorem and van der Waerden's theorem are two classical Ramsey theoretic results, the first one deals with finite configurations and the second one deals with infinite configurations. The Central Sets Theorem due to Furstenberg is a strong simultaneous extension of both theorems, which also applies to general commutative semigroups. Beiglboeck provided a common extension of the Central Sets Theorem and Milliken-Taylor Theorem in commutative case. Furstenberg's original Central Sets Theorem was proved in \cite{key-2} for $\left(\mathbb{N},+\right)$ for finitely many sequences at a time. Bergelson and Hindman provided a non commutative version of this Theorem \cite{key-3}. The first author of this article jointly with Hindman and Straus provided a non-commutative version of Central Sets Theorem using arbitrary many sequence at a time \cite{key-5}. In this work we will provide a non-commutative extension of Beiglboeck's Theorem. We also provide polynomial generalization of Beiglbock's theorem.

math.CO↗

arXiv2024

Abundance of arithmetic progressions in $\mathcal{CR}$-sets

H.Furstenberg and E.Glasner proved that for an arbitrary $k\in\mathbb{N}$, any piecewise syndetic set of integers contains a $k$-term arithmetic progression and the collection of such progressions is itself piecewise syndetic in $\mathbb{Z}.$ The above result was extended for arbitrary semigroups by V. Bergelson and N. Hindman, using the algebra of the Stone-Čech compactification of discrete semigroups. However, they provided an abundance for various types of large sets. In \cite{DHS}, the first author, Neil Hindman and Dona Strauss introduced two notions of large sets, namely, $J$-set and $C$-set. In \cite{BG}, V. Bergelson and D. Glasscock introduced another notion of largeness, which is analogous to the notion of $J$-set, namely $\mathcal{CR}$- set. All these sets contain arithmetic progressions of arbitrary length. In \cite{DG}, the second author and S. Goswami proved that for any $J$-set, $A\subseteq\mathbb{N}$, the collection $\{(a,b):\,\{a,a+b,a+2b,\ldots,a+lb\}\subset A\}$ is a $J$-set in $(\mathbb{N\times\mathbb{N}},+)$. In this article, we prove the same for $\mathcal{CR}$-sets.

math.CO↗

arXiv2021

Elementary characterization of essential F-sets and its combinatorial consequences

There is a long history of studying Ramsey theory using the algebraic structure of the Stone-Čech compactification of discrete semigroup. It has been shown that various Ramsey theoretic structures are contained in different algebraic large sets. In this article we will deduce the combinatorial characterization of certain sets, that are the member of the idempotent ultrafilters of the closed subsemigroup of $βS$, arising from certain Ramsey family. In a special case when $S=\mathbb{N}$, we will deduce that sets which are the members of all idempotent ultrafilters of those semigroups contain certain additive-multiplicative structures. Later we will generalize this result for weak rings, where we will show a non-commutative version of the additive-multiplicative structure.

math.GN↗

arXiv2018

Estimation of recurrence for nilpotent group action

We estimate size of recurrence of an action of a nilpotent group by homeomorphisms of a compact space for polynomial mappings into a nilpotent group form the partial semigroup $(\mathcal{P}_{f}(\mathbb{N}),\uplus)$. To do this we have used algebraic structure of the Stone-Čech copactification partial semigroup and that of the given nilpotent group.

math.GN↗

arXiv2017

IP$^{*}$-sets in function field and mixing properties

The ring of polynomial over a finite field $F_q[x]$ has received much attention, both from a combinatorial viewpoint as in regards to its action on measurable dynamical systems. In the case of $(\mathbb{Z},+)$ we know that the ideal generated by any nonzero element is an IP$^*$-set. In the present article we first establish that the analogous result is true for $F_q[x]$. We further use this result to establish some mixing properties of the action of $(F_q[x],+)$. We shall also discuss on Khintchine's recurrence for the action of $(F_q[x]\setminus\{0\},\cdot)$.

math.DS↗

arXiv2014

Large Sets in Countable Amenable Group and its Applications

In the present paper our main objective is to extend the notion of $D$-sets in countable amenable groups and to discuss its connection with weak mixing for amenable group actions. Further we prove that *-notions are equivalent in the countable amenable group of polynomials generated by finite fields.

math.DS↗

arXiv2014

Additive and multiplicative structure of c$^{\star}$-sets

It is known that for an IP${^\star}$ set $A$ in $\mathbb{N}$ and a sequence $< x_{n}>_{n=1}^{\infty}$ there exists a sum subsystem $< y_{n}>_{n=1}^{\infty}$ of $< x_{n}>_{n=1}^{\infty}$ such that $FS(< y_n>_{n=1}^\infty)\cup FP(< y_n>_{n=1}^\infty)\subseteq A$. Similar types of results also have been proved for central* sets where the sequences have been taken from the class of minimal sequences. In this present work we will prove some analogues results for C$^{\star}$-sets for a more general class of sequences.

math.CO↗

arXiv2013

Centrally Image partition Regularity near 0

The notion of Image partition regularity near zero was first introduced by De and Hindman. It was shown there that like image partition regularity over $\mathbb{N}$ the main source of infinite image partition regular matrices near zero are Milliken- Taylor matrices. But Milliken- Taylor matrices are far apart to have images in central sets. In this regard the notion of centrally image partition regularity was introduced. In the present paper we propose the notion centrally partition regular matrices near zero for dense sub semigroup of $(\ber^+,+)$ which are different from centrally partition regular matrices unlike finite cases.

math.CO↗

arXiv2012

Combined algebraic and multiplicative properties near zero

It was proved that whenever $\mathbb{N}$ is partitioned into finitely many cells, one cell must contain arbitrary length arithmetic and geometric progression nicely intertwined, so that one cell must be rich in the sense of containing substantial combined additive and multiplicative properties. Further it is known that IP$^*$ and central$^*$ sets are also rich in substantial combined additive and multiplicative properties but not partition regular. In this article we prove that these types of results also hold near zero for dense subsemigroups $S$ of $((0,\infty),+)$ for which $(S\cap(0,1),\cdot)$.

math.CO↗