This paper is a continuation and complement for previous works on selective covering properties. We introduce the novel concept of the nearly Menger property in a bitopological context. We demonstrate its interrelations with existing covering properties and construct certain equivalences between those. We also investigate various properties of nearly Menger bitopological spaces by considering it under subspaces, products, and certain type of mappings.
Citation: Necati Can Açıkgöz, Ceren Sultan Elmalı. Nearly Menger covering property via bitopological spaces[J]. AIMS Mathematics, 2024, 9(12): 34042-34066. doi: 10.3934/math.20241623
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This paper is a continuation and complement for previous works on selective covering properties. We introduce the novel concept of the nearly Menger property in a bitopological context. We demonstrate its interrelations with existing covering properties and construct certain equivalences between those. We also investigate various properties of nearly Menger bitopological spaces by considering it under subspaces, products, and certain type of mappings.
Fibonacci polynomials and Lucas polynomials are important in various fields such as number theory, probability theory, numerical analysis, and physics. In addition, many well-known polynomials, such as Pell polynomials, Pell Lucas polynomials, Tribonacci polynomials, etc., are generalizations of Fibonacci polynomials and Lucas polynomials. In this paper, we extend the linear recursive polynomials to nonlinearity, that is, we discuss some basic properties of the bi-periodic Fibonacci and Lucas polynomials.
The bi-periodic Fibonacci {fn(t)} and Lucas {ln(t)} polynomials are defined recursively by
f0(t)=0,f1(t)=1,fn(t)={ayfn−1(t)+fn−2(t)n≡0(mod2),byfn−1(t)+fn−2(t)n≡1(mod2),n≥2, |
and
l0(t)=2,l1(t)=at,ln(t)={byln−1(t)+ln−2(t)n≡0(mod2),ayln−1(t)+ln−2(t)n≡1(mod2),n≥2, |
where a and b are nonzero real numbers. For t=1, the bi-periodic Fibonacci and Lucas polynomials are, respectively, well-known bi-periodic Fibonacci {fn} and Lucas {ln} sequences. We let
ς(n)={0n≡0(mod2),1n≡1(mod2),n≥2. |
In [1], the scholars give the Binet formulas of the bi-periodic Fibonacci and Lucas polynomials as follows:
fn(t)=aς(n+1)(ab)⌊n2⌋(σn(t)−τn(t)σ(t)−τ(t)), | (1.1) |
and
ln(t)=aς(n)(ab)⌊n+12⌋(σn(t)+τn(t)), | (1.2) |
where n≥0, σ(t), and τ(t) are zeros of λ2−abtλ−ab. This is σ(t)=abt+√a2b2t2+4ab2 and τ(t)=abt−√a2b2t2+4ab2. We note the following algebraic properties of σ(t) and τ(t):
σ(t)+τ(t)=abt,σ(t)−τ(t)=√a2b2t2+4ab,σ(t)τ(t)=−ab. |
Many scholars studied the properties of bi-periodic Fibonacci and Lucas polynomials; see [2,3,4,5,6]. In addition, many scholars studied the power sums problem of second-order linear recurrences and its divisible properties; see [7,8,9,10].
Taking a=b=1 and t=1, we obtain the Fibonacci {Fn} or Lucas {Ln} sequence. Melham [11] proposed the following conjectures:
Conjecture 1. Let m≥1 be an integer, then the sum
L1L3L5⋯L2m+1n∑k=1F2m+12k |
can be represented as (F2n+1−1)2R2m−1(F2n+1), including R2m−1(t) as a polynomial with integer coefficients of degree 2m−1.
Conjecture 2. Let m≥1 be an integer, then the sum
L1L3L5⋯L2m+1n∑k=1L2m+12k |
can be represented as (L2n+1−1)Q2m(L2n+1), where Q2m(t) is a polynomial with integer coefficients of degree 2m.
In [12], the authors completely solved the Conjecture 2 and discussed the Conjecture 1. Using the definition and properties of bi-periodic Fibonacci and Lucas polynomials, the power sums problem and their divisible properties are studied in this paper. The results are as follows:
Theorem 1. We get the identities
n∑k=1f2m+12k(t)=a2m+1b(a2b2t2+4ab)mm∑j=0(−1)m−j(2m+1m−j)(f(2n+1)(2j+1)(t)−f2j+1(t)l2j+1(t)), | (1.3) |
n∑k=1f2m+12k+1(t)=(ab)m(a2b2t2+4ab)mm∑j=0(2m+1m−j)(f(2n+2)(2j+1)(t)−f2(2j+1)(t)l2j+1(t)), | (1.4) |
n∑k=1l2m+12k(t)=m∑j=0(2m+1m−j)(l(2n+1)(2j+1)(t)−l2j+1(t)l2j+1(t)), | (1.5) |
n∑k=1l2m+12k+1(t)=am+1bm+1m∑j=0(−1)m−j(2m+1m−j)(l(2n+2)(2j+1)(t)−l2(2j+1)(t)l2j+1(t)), | (1.6) |
where n and m are positive integers.
Theorem 2. We get the identities
n∑k=1f2m2k(t)=a2m(a2b2t2+4ab)mm∑j=0(−1)m−j(2mm−j)f2j(2n+1)(t)f2j(t)−a2m(a2b2t2+4ab)m(2mm)(−1)m(n+12), | (1.7) |
n∑k=1f2m2k+1(t)=(ab)m(a2b2t2+4ab)mm∑j=0(2mm−j)(f2j(2n+2)(t)−f4j(t)f2j(t))−(ab)m(a2b2t2+4ab)m(2mm)n, | (1.8) |
n∑k=1l2m2k(t)=m∑j=0(2mm−j)f2j(2n+1)(t)l2j+1(t)−22m−1−(2mm)(n+12), | (1.9) |
n∑k=1l2m2k+1(t)=ambmm∑j=0(−1)m−j(2mm−j)(f2j(2n+2)(t)−f4j(t)f2j(t))−ambm(2mm)(−1)mn, | (1.10) |
where n and m are positive integers.
As for application of Theorem 1, we get the following:
Corollary 1. We get the congruences:
bl1(t)l3(t)⋯l2m+1(t)n∑k=1f2m+12k(t)≡0(modf2n+1(t)−1), | (1.11) |
and
al1(t)l3(t)⋯l2m+1(t)n∑k=1l2m+12k(t)≡0(modl2n+1(t)−at), | (1.12) |
where n and m are positive integers.
Taking t=1 in Corollary 1, we have the following conclusions for bi-periodic Fibonacci {fn} and Lucas {ln} sequences.
Corollary 2. We get the congruences:
bl1l3⋯l2m+1n∑k=1f2m+12k≡0(modf2n+1−1), | (1.13) |
and
al1l3⋯l2m+1n∑k=1l2m+12k≡0(modl2n+1−a), | (1.14) |
where n and m are nonzero real numbers.
Taking a=b=1 and t=1 in Corollary 1, we have the following conclusions for bi-periodic Fibonacci {Fn} and Lucas {Ln} sequences.
Corollary 3. We get the congruences:
L1L3⋯L2m+1n∑k=1F2m+12k≡0(modF2n+1−1), | (1.15) |
and
L1L3⋯L2m+1n∑k=1L2m+12k≡0(modL2n+1−1), | (1.16) |
where n and m are nonzero real numbers.
To begin, we will give several lemmas that are necessary in proving theorems.
Lemma 1. We get the congruence
f(2n+1)(2j+1)(t)−f2j+1(t)≡0(modf2n+1(t)−1), |
where n and m are nonzero real numbers.
Proof. We prove it by complete induction for j≥0. This clearly holds when j=0. If j=1, we note that abf3(2n+1)(t)=(a2b2t2+4ab)f32n+1(t)−3abf2n+1(t) and we obtain
f3(2n+1)(t)−f3(t)=(abt2+4)f32n+1(t)−3f2n+1(t)−(abt2+4)f31(t)+3f1(t)=(abt2+4)(f2n+1(t)−f1(t))(f22n+1(t)+f2n+1(t)f1(t)+f21(t))−3(f2n+1(t)−f1(t))=(abt2+4)(f2n+1(t)−1)(f22n+1(t)+f2n+1(t)f1(t)+f21(t))−3(f2n+1(t)−1)≡0(modf2n+1(t)−1). |
This is obviously true when j=1. Assuming that Lemma 1 holds if j=1,2,…,k, that is,
f(2n+1)(2j+1)(t)−f2j+1(t)≡0(modf2n+1(t)−1). |
If j=k+1≥2, we have
l2(2n+1)(t)f(2n+1)(2j+1)(t)=f(2n+1)(2j+3)(t)+abf(2n+1)(2j−1)(t), |
and
abl2(2n+1)(t)=(a2b2t2+4ab)f22n+1(t)−2ab≡(a2b2t2+4ab)f21(t)−2ab(modf2n+1(t)−1). |
We have
f(2n+1)(2k+3)(t)−f2k+3(t)=l2(2n+1)(t)f(2n+1)(2k+1)(t)−abf(2n+1)(2k−1)(t)−l2(t)f2k+1(t)+abf2k−1(t)≡((abt2+4)f21(t)−2)f(2n+1)(2k+1)(t)−abf(2n+1)(2k−1)(t)−((abt2+4)f21(t)−2)f2k+1(t)+abf2k−1(t)≡((abt2+4)f21(t)−2)(f(2n+1)(2k+1)(t)−f2k+1(t))−ab(f(2n+1)(2k−1)(t)−f2k−1(t))≡0(modf2n+1(t)−1). |
This completely proves Lemma 1.
Lemma 2. We get the congruence
al(2n+1)(2j+1)(t)−al2j+1(t)≡0(modl2n+1(t)−at), |
where n and m are nonzero real numbers.
Proof. We prove it by complete induction for j≥0. This clearly holds when j=0. If j=1, we note that al3(2n+1)(t)=bl32n+1(t)+3al2n+1(t) and we obtain
al3(2n+1)(t)−al3(t)=bl32n+1(t)+3al2n+1(t)−bl31(t)−3al1(t)=(l2n+1(t)−l1(t))(bl22n+1(t)+bl2n+1(t)l1(t)+bl21(t))−3a(l2n+1(t)−l1(t))=(l2n+1(t)−at)(bl22n+1(t)+bayl2n+1(t)+ba2t2)−3a(l2n+1(t)−at)≡0(modl2n+1(t)−at). |
This is obviously true when j=1. Assuming that Lemma 2 holds if j=1,2,…,k, that is,
al(2n+1)(2j+1)(t)−al2j+1(t)≡0(modl2n+1(t)−at). |
If j=k+1≥2, we have
l2(2n+1)(t)l(2n+1)(2j+1)(t)=l(2n+1)(2j+3)(t)+l(2n+1)(2j−1)(t), |
and
al2(2n+1)(t)=bl22n+1(t)+2a≡bl21(t)+2a(modl2n+1(t)−at). |
We have
al(2n+1)(2k+3)(t)−al(2k+3)(t)=a(l2(2n+1)(t)l(2n+1)(2k+1)(t)−l(2n+1)(2k−1)(t))−a(l2(t)l2k+1(t)−l2k−1(t))≡(bl21(t)+2a)l(2n+1)(2k+1)(t)−al(2n+1)(2k−1)(t)−(bl21(t)+2a)l2k+1(t)+al2k−1(t)≡(abt2+2)(al(2n+1)(2k+1)(t)−al2k+1(t))−(al(2n+1)(2k−1)(t)−al2k−1(t))≡0(modl2n+1(t)−at). |
This completely proves Lemma 2.
Proof of Theorem 1. We only prove (1.3), and the proofs for other identities are similar.
n∑k=1f2m+12k(t)=n∑k=1(aς(2k+1)(ab)⌊2k2⌋⋅(σ2k(t)−τ2k(t)σ(t)−τ(t)))2m+1=a2m+1(σ(t)−τ(t))2m+1n∑k=1(σ2k(t)−τ2k(t))2m+1(ab)(2m+1)k=a2m+1(σ(t)−τ(t))2m+1n∑k=12m+1∑j=0(−1)j(2m+1j)σ2k(2m+1−j)(t)τ2kj(t)(ab)(2m+1)k=a2m+1(σ(t)−τ(t))2m+12m+1∑j=0(−1)j(2m+1j)(1−σ2n(2m+1−2j)(t)(ab)(2m+1−2j)n(ab)2m+1−2jσ2(2m+1−2j)(t)−1)=a2m+1(σ(t)−τ(t))2m+1m∑j=0(−1)j(2m+1j)(1−σ2n(2m+1−2j)(t)(ab)(2m+1−2j)n(ab)2m+1−2jσ2(2m+1−2j)(t)−1−1−σ2n(2j−1−2m)(t)(ab)(2j−1−2m)n(ab)2j−1−2mσ2(2j−1−2m)(t)−1)=a2m+1(σ(t)−τ(t))2m+1m∑j=0(−1)j(2m+1j)(σ2(2m+1−2j)(t)(ab)2m+1−2j−σ(2n+2)(2m+1−2j)(t)(ab)(n+1)(2m+1−2j)+1−σ2n(2j−1−2m)(t)(ab)(2j−1−2m)n1−σ2(2m+1−2j)(t)(ab)(2m+1−2j))=a2m+1(σ(t)−τ(t))2m+1m∑j=0(−1)j(2m+1j)×(σ2m+1−2j(t)−τ2m+1−2j(t)−σ(2n+1)(2m+1−2j)(t)(ab)(2m+1−2j)n+τ(2n+1)(2m+1−2j)(t)(ab)(2m+1−2j)n−σ2m+1−2j(t)−τ2m+1−2j(t))=a2m+1b(a2b2t2+4ab)mm∑j=0(−1)m−j(2m+1m−j)(f(2n+1)(2j+1)(t)−f2j+1(t)l2j+1(t)). |
Proof of Theorem 2. We only prove (1.7), and the proofs for other identities are similar.
n∑k=1f2m2k(t)=n∑k=1(aς(2k+1)(ab)⌊2k2⌋⋅(σ2k(t)−τ2k(t)σ(t)−τ(t)))2m=a2m(σ(t)−τ(t))2mn∑k=1(σ2k(t)−τ2k(t))2m(ab)2mk=a2m(σ(t)−τ(t))2mn∑k=12m∑j=0(−1)j(2mj)σ2k(2m−j)(t)τ2kj(t)(ab)2mk=a2m(σ(t)−τ(t))2m2m∑j=0(−1)j(2mj)(1−σ2n(2m−2j)(t)(ab)(2m−2j)n(ab)2m−2jσ2(2m−2j)(t)−1) |
=a2m(σ(t)−τ(t))2mm∑j=0(−1)j(2mj)(1−σ2n(2m−2j)(t)(ab)(2m−2j)n(ab)2m−2jσ2(2m−2j)(t)−1+1−σ2n(2j−2m)(t)(ab)(2j−2m)n(ab)2j−2mσ2(2j−2m)(t)−1)+a2m(σ(t)−τ(t))2m(−1)m+1(2mm)n=a2m(σ(t)−τ(t))2mm∑j=0(−1)j(2mj)(σ2(2m−2j)(t)(ab)2m−2j−σ(2n+2)(2m−2j)(t)(ab)(n+1)(2m−2j)−1+σ2n(2j−2m)(t)(ab)(2j−2m)n1−σ2(2m−2j)(t)(ab)2m−2j)+a2m(σ(t)−τ(t))2m(−1)m+1(2mm)n=a2m(σ(t)−τ(t))2mm∑j=0(−1)j(2mj)(σ2m−2j(t)−τ2m−2j(t)−σ(2n+1)(2m−2j)(t)(ab)n(2m−2j)+τ(2n+1)(2m−2j)(t)(ab)n(2m−2j)τ2m−2j(t)−σ2m−2j(t))+a2m(σ(t)−τ(t))2m(−1)m+1(2mm)n=a2m(a2b2t2+4ab)mm∑j=0(−1)m−j(2mm−j)(f2j(2n+1)(t)−f2j(t)f2j(t))+a2m(a2b2t2+4ab)m(−1)m+1(2mm)n. |
Proof of Corollary 1. First, from the definition of fn(t) and binomial expansion, we easily prove (f2n+1(t)−1,a2b2t2+4ab)=1. Therefore, (f2n+1(t)−1,(a2b2t2+4ab)m)=1. Now, we prove (1.11) by Lemma 1 and (1.3):
bl1(t)l3(t)⋯l2m+1(t)n∑k=1f2m+12k(t)=l1(t)l3(t)⋯l2m+1(t)(a2m+1(σ(t)−τ(t))2mm∑j=0(−1)m−j(2m+1m−j)(f(2n+1)(2j+1)(t)−f2j+1(t)l2j+1(t)))≡0(modf2n+1(t)−1). |
Now, we use Lemma 2 and (1.5) to prove (1.12):
al1(t)l3(t)⋯l2m+1(t)n∑k=1l2m+12k(t)=l1(t)l3(t)⋯l2m+1(t)(m∑j=0(2m+1m−j)(al(2n+1)(2j+1)(t)−al2j+1(t)l2j+1(t)))≡0(modl2n+1(t)−at). |
In this paper, we discuss the power sums of bi-periodic Fibonacci and Lucas polynomials by Binet formulas. As corollaries of the theorems, we extend the divisible properties of the sum of power of linear Fibonacci and Lucas sequences to nonlinear Fibonacci and Lucas polynomials. An open problem is whether we extend the Melham conjecture to nonlinear Fibonacci and Lucas polynomials.
The authors declare that they did not use Artificial Intelligence (AI) tools in the creation of this paper.
The authors would like to thank the editor and referees for their helpful suggestions and comments, which greatly improved the presentation of this work. All authors contributed equally to the work, and they have read and approved this final manuscript. This work is supported by Natural Science Foundation of China (12126357).
The authors declare that there are no conflicts of interest regarding the publication of this paper.
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