- Research
- Open access
- Published:
Existence and multiplicity of solutions for boundary value problem of singular two-term fractional differential equation with delay and sign-changing nonlinearity
Boundary Value Problems volume 2023, Article number: 114 (2023)
Abstract
In this paper, we consider the existence of solutions for a boundary value problem of singular two-term fractional differential equation with delay and sign-changing nonlinearity. By means of the Guo–Krasnosel’skii fixed point theorem and the Leray–Schauder nonlinear alternative theorem, we obtain some results on the existence and multiplicity of solutions, respectively.
1 Introduction
In this paper, we study the following two-term fractional differential equation with delay:
where \(n-1<\alpha <n\), \(n=[\alpha ]+1\), \(n\geq 3\) (\(n\in N\)), \(a>0\), \(D^{\alpha}_{0^{+}}\) is the standard Riemann–Liouville fractional derivative, λ is a positive constant, \(f(t,x):(0,1)\times R^{+} \rightarrow R\) is continuous, may change sign, and be singular at \(t=0\), \(t=1\), and \(x=0\), where \(R^{+}=(0,+\infty )\), \(\eta \in C[-\tau ,0]\), and \(\eta (t)>0\) for \(t\in [-\tau ,0)\), \(\eta (0)=0\).
Recently, fractional differential equations have been extensively studied, among which the existence of positive solutions to fractional differential equations was considered in [1, 8, 10–12, 15, 16, 19, 20] and [6, 22]. In particular, the nonlinear terms of the problems studied in [8, 10–12, 19] can change sign and are singular at time or space variables. In practical problems, delay is a nonnegligible factor, which can reasonably express the influence of the past on the present. Therefore the delay differential equation has a wide range of applications in control theory, signal processing, biology, finance, and many other fields [4, 10, 12, 14, 21]. In addition, unlike the above research problems, the fractional differential equations of two terms are studied in [2, 3, 17, 18].
Mu et al. [12] investigated the singular boundary value problems for the following nonlinear fractional differential equations with delay by the Guo–Krasnosel’skii fixed point theorem:
where \(2<\alpha \leq 3\), \(D^{\alpha}\) is the standard Riemann–Liouville derivative, λ is a positive constant, and \(f(t,x)\) may change sign and be singular at \(t=1\), \(t=0\), and \(x=0\).
Liu and Zhang [10] considered the existence of a positive solution for the following problem:
where \(n-1<\alpha \leq n\), \(n=[\alpha ]+1\), \(D^{\alpha}_{0^{+}}\) is the standard Riemann–Liouville fractional derivative, \(\tau \in (0,1)\), \(f(t,x):(0,1)\times R^{+} \rightarrow R\) is continuous, may change sign, and be singular at \(t=0\), \(t=1\), and \(x=0\), where \(R^{+}=(0,+\infty )\), \(\eta \in C[-\tau ,0]\), \(\eta (t)>0\) for \(t\in [-\tau ,0)\), and \(\eta (0)=0\).
Wang [17] considered a class of Riemann–Liouville type two-term fractional boundary value problems:
where \(2<\alpha <3\), \(a>0\), and \(D^{\alpha}_{0^{+}}\) is the standard Riemann–Liouville derivative. Some positive properties of the Green’s function are deduced by using techniques of analysis, and two applications are given by the Guo–Krasnosel’skii fixed point theorem and monotone iterative technique.
Compared with problems (1.2) and (1.3), we discuss the two-term fractional differential equation and show that problem (1.1) has at least two positive solutions. Problem (1.1) is a generalization of the problem studied in [17] when \(\tau =0\) and \(n=3\). By means of the Guo–Krasnosel’skii fixed point theorem and the Leray–Schauder nonlinear alternative theorem we obtaim the existence of at least two positive solutions or three nontrivial solutions of (1.1), respectively.
This paper is organized as follows. In Sect. 2, we introduce some definitions and give preliminary results to be used in the proof of our main theorems. In Sect. 3, we establish the existence and multiplicity of solutions for problem (1.1) based on some fixed point theorems.
2 Basic definitions and preliminaries
In this section, we introduce some basic definitions, theorems, and lemmas.
Definition 2.1
([13]) The Riemann–Liouville fractional integral of order \(\alpha >0\) for a function f is defined as
provided that the right-hand side is pointwise defined on \((0,+\infty )\), where Γ is the gamma function defined by
Definition 2.2
([13]) The Riemann–Liouville fractional derivative of order α (\(n-1<\alpha <n\)) for a function f is defined as
provided that the right-hand side is pointwise defined on \((0,+\infty )\), where \(n=[\alpha ]+1\), \([\alpha ]\) denotes the integer part of number α, and Γ is the gamma function.
For convenience, we give the following notations:
where
is the Mittag-Leffler function.
By (2.1) we know that h is strictly increasing on \([0,+\infty )\), \(h(0)<0\), and
Then h has a unique positive root \(a^{*}\), that is, \(h(a^{*})=0\).
- \((\textbf{H}_{1})\):
-
\(a\in (0,a^{*}]\) is a constant.
Lemma 2.3
([9]) Let \(n-1<\alpha \leq n\) (\(n\in \mathbb{N}\)), let \(\lambda \in \mathbb{R}\), and let y be a real function on \(\mathbb{R}\). Then the equation
is solvable, and its general solution is given by
with arbitrary \(c_{j}\in \mathbb{R}\), \(j=1,\dots , n\), where \(E_{\alpha ,\beta}\) is the Mittag-Leffler function.
Lemma 2.4
Let \(n-1<\alpha \leq n\) and \(y\in L^{1}[0,1]\cap C(0,1)\). Then the unique solution of the two-term boundary value problem
is given by
where
Proof
By Lemma 2.3 we know that the general solution of the equation
can be expressed by
Since \(u(0)=u'(0)=\cdots =u^{(n-1)}(0)=0\), we deduce that \(c_{n}=c_{n-1}=\cdots =c_{2}=0\).
It follows from \(u(1)=0\) that
Therefore the solution of (2.4) is
This completes the proof. □
Lemma 2.5
For \(0\leq s\leq t\leq 1\), we have \(g_{n-2}(t)g_{n-2}(1-s)\geq g_{n-2}(t-s)g_{n-2}(1)\).
Proof
For \(t>0\), by (2.3) we have
Therefore \(g_{n-2}(t)\) is strictly increasing on \([0,1]\).
By calculation we have
Then \(g'_{n-2}(t)\) is strictly decreasing on \([0,1]\), and
Therefore we get
that is,
This completes the proof. □
Lemma 2.6
The Green’s function \(G(t,s)\) satisfies the following properties:
-
(1)
\(G(t,s)>0\), \(t,s\in (0,1)\);
-
(2)
\(G(t,s)=G(1-s,1-t)\), \(t,s\in [0,1]\);
-
(3)
\(G(t,s)\geq M_{1}s(1-s)^{\alpha -1}(1-t)t^{\alpha -1}\), \(t,s \in [0,1]\);
-
(4)
\(G(t,s)\leq M_{2}s(1-s)^{\alpha -1}\) \(t,s\in [0,1]\).
where
and \(s^{*}\in (0,1)\) satisfies \(s^{*}=(1-s^{*})^{\alpha -2}\).
Proof
Since (2) is obviously true, (1) can be deduced from (3), and the proof for (4) is the same as that in [17], so that we just verify (3).
(3) For \(t\in [0,1]\), by (2.3) we have
For \(0\leq t\leq s\leq 1\), the proof is similar to that in [17], and we omit it here.
For \(0\leq s\leq t\leq 1\), in view of (2.2), (2.3), and Lemma 2.5, we have that
and then
This completes the proof. □
Remark 2.7
\(G(t,s)\leq M_{2}(1-t)t^{\alpha -1}\), \(t,s\in [0,1]\).
Lemma 2.8
([7]) Let E be a Banach space, and let \(K\subset E\) be a cone. Let \(\Omega _{1}\) and \(\Omega _{2}\) be open bounded subsets of E with \(\theta \in \Omega _{1}\) such that \(\overline{\Omega}_{1}\subset \Omega _{2}\), and let \(T:K\cap (\overline{\Omega}_{2}\backslash \Omega _{1})\rightarrow K\) be a completely continuous operator such that
-
(i)
\(\Vert Tu\Vert \leq \Vert u\Vert \), \(u\in K \cap \partial \Omega _{1}\), and \(\Vert Tu\Vert \geq \Vert u\Vert \), \(u\in K\cap \partial \Omega _{2}\);
or
-
(ii)
\(\Vert Tu\Vert \geq \Vert u\Vert \), \(u\in K \cap \partial \Omega _{1}\), and \(\Vert Tu\Vert \leq \Vert u\Vert \), \(u\in K\cap \partial \Omega _{2}\).
Then T has a fixed point in \(K\cap (\overline{\Omega}_{2}\backslash \Omega _{1})\).
Lemma 2.9
([5]) Let Ω be a relatively open subset of a convex set C in a Banach space E. Let \(T:\overline{\Omega}\rightarrow C\) be a compact map, and let \(p\in \Omega \). Then either
-
(1)
T has a fixed point in Ω̅,
or
-
(2)
there are \(x\in \partial \Omega \) and \(\lambda \in (0,1)\) such that \(x=(1-\lambda )p+\lambda Tx\).
3 Main results
In this section, we discuss the existence and multiplicity of positive solutions for the boundary value problem (1.1).
For convenience, we always suppose that the following two conditions hold:
- \((\textbf{H}_{2})\):
-
There exists a nonnegative function \(\rho \in C(0,1)\cap L[0,1]\) such that \(\int ^{1}_{0}\rho (s)\,ds>0\),
$$ f(t,x)>-\rho (t), $$and
$$ \varphi _{2}(t)h_{2}(x)\leq f(t,x)+\rho (t)\leq \varphi _{1}(t) \bigl(J(x)+h_{1}(x)\bigr),\quad (t,x) \in (0,1)\times R^{+}, $$where \(\varphi _{1}, \varphi _{2}\in L[0,1]\) are nonnegative, \(h_{1}, h_{2}\in C(R^{+}_{0},R^{+})\) are nondecreasing, \(J\in C(R^{+},R^{+})\) is nonincreasing (\(R^{+}_{0}=[0,+\infty )\));
- \((\textbf{H}_{3})\):
-
$$ 0< \int ^{\tau}_{0}s(1-s)^{\alpha -1}\varphi _{1}(s)J\bigl(\eta (s-\tau )\bigr)\,ds< + \infty , $$
and there exists a constant \(b>0\) such that
$$ \int _{\tau}^{1}s(1-s)^{\alpha -1}\varphi _{1}(s)J\biggl((s-\tau )^{\alpha -1}\bigl[1-(s- \tau )\bigr] \frac{3M_{1}b}{4M_{2}}\biggr)\,ds< +\infty , $$where \(M_{1}\) and \(M_{2}\) are as in Lemma 2.6.
Remark 3.1
Let \(A=\max_{-\tau \leq t\leq 0}\eta (t)\); when \(s\in [0,\tau ]\), we have \(-\tau \leq s-\tau \leq 0\), and then \(0\leq \eta (s-\tau )\leq A\).
Let \(X=\{x|x\in C[-\tau ,1]\}\). Then \((X,\Vert \cdot \Vert )\) is a Banach space with the maximum norm
Define the cone
and let
The restriction \(\omega | _{[0,1]}\) of ω on \([0,1]\) is the solution of the following liner equation:
Then \(\omega (t)=\lambda \int ^{1}_{0}G(t,s)\rho (s)\,ds\), and by Remark 2.7 we get
where \(c=\lambda M_{2}\int ^{1}_{0}\rho (s)\,ds\).
It is easy to see that x is a solution of boundary value problem (1.1) if and only if it satisfies
Then we consider the following operator:
Let
where \(r_{1}\), \(r_{2}\), \(r_{3}\) satisfies
Lemma 3.2
Suppose \((H_{1})\)–\((H_{3})\) hold. Then the operator \(T:K\cap (\bar{\Omega}_{r_{3}}\backslash \Omega _{r_{1}}) \rightarrow K\) is completely continuous.
Proof
Step 1. We will show that T is well-defined on \(K\cap (\bar{\Omega}_{r_{3}}\backslash \Omega _{r_{1}})\).
For any \(x\in K\cap (\bar{\Omega}_{r_{3}}\backslash \Omega _{r_{1}})\), we have \(r_{1}\leq \Vert x\Vert \leq r_{3}\), and
and by (3.2) we get
Then by \((H_{2})\), \((H_{3})\), (3.4), Remark 3.1, and Lemma 2.6 we obtain
Therefore T is well-defined on \(K\cap (\bar{\Omega}_{r_{3}}\setminus \Omega _{r_{1}})\).
Step 2. We will show that \(T:K\cap (\bar{\Omega}_{r_{3}}\backslash \Omega _{r_{1}}) \rightarrow K\).
For any \(x\in K\cap (\bar{\Omega}_{r_{3}}\backslash \Omega _{r_{1}})\) and \(t\in [-\tau ,0]\), by (3.3) we know that \(Tx(t)=0\).
For any \(x\in K\cap (\bar{\Omega}_{r_{3}}\backslash \Omega _{r_{1}})\) and \(t\in [0,1]\), we have
that is,
Hence \(T:K\cap (\bar{\Omega}_{r_{3}}\backslash \Omega _{r_{1}}) \rightarrow K\).
Step 3. Now let us prove that \(T:K\cap (\bar{\Omega}_{r_{3}}\backslash \Omega _{r_{1}}) \rightarrow K\) is a continuous operator.
For all \(x_{n}, x\in K\cap (\bar{\Omega}_{r_{3}}\backslash \Omega _{r_{1}})\), \(n=1,2, \dots \) with \(\Vert x_{n}-x\Vert _{[-\tau ,1]}\rightarrow 0\) as \(n\rightarrow +\infty \), we have
and for any \(t\in [0,1]\),
By \((H_{2})\) we get that
and, similarly,
Then
and
By the Lebesgue dominated convergence theorem it follows that
which implies that \(\Vert Tx_{n}-Tx\Vert _{[-\tau ,1]}\rightarrow 0\) as \(n\rightarrow +\infty \). Hence T is a continuous operator.
Step 4. Finally, we will prove that T is a compact operator.
Let \(B\subset K\cap (\bar{\Omega}_{r_{3}}\backslash \Omega _{r_{1}})\) be any nonempty bounded set.
Firstly, we prove that \(T(B)\) is uniformly bounded.
For any \(x\in B\), by (3.5) we can easily get that
Therefore \(T(B)\) is uniformly bounded.
Secondly, we prove that \(T(B)\) is equicontinuous.
Since \(G(t,s)\) is uniformly continuous for \((t,s)\in [0,1]\times [0,1]\), it follows that for any \(\varepsilon >0\), there exists \(\delta _{0}>0\) such that for \(t_{1}, t_{2}, s\in [0,1]\), if \(| t_{1}-t_{2}| <\delta _{0}\), then
Therefore by \((H_{2})\) and Remark 3.1 we get that for any \(x\in B\),
Thus \(T(B)\) is equicontinuous.
By the Ascoli–Arzelà theorem, \(T(B)\) is a sequentially compact set, and thus T is a completely continuous operator. This completes the proof. □
It is clear that if x̃ is a fixed point of operator T in (3.3), then by Lemma 2.4 we obtain that
If
then
Let
Lemma 3.3
If \(\tilde{x}(t)=x(t)+\omega (t)-\bar{\eta}(t)\) is a positive solution of boundary value problem (3.6) and the inequality \(\tilde{x}(t)-\omega (t)+\bar{\eta}(t)\geq 0\) holds for \(t\in (0,1)\setminus \{\tau \}\), then \(x(t)\) is a positive solution of boundary value problem (1.1).
Proof
If \(\tilde{x}(t)\) is a positive solution of boundary value problem (3.6) and \(\tilde{x}(t)-\omega (t)+\bar{\eta}(t)\geq 0\) for \(t\in (0,1)\setminus \{\tau \}\), then for \(t\in [-\tau ,0]\), we have
For \(t\in (0,1)\setminus \{\tau \}\), by (3.6) and (3.8) we have
It is clear that \(x(t)\) is the solution of problem (1.1). This completes the proof. □
To prove the main results, we give the following two conditions.
- \((\textbf{H}_{4})\):
-
There exists \([d,e]\subset (\tau ,1)\) such that \(\int ^{e}_{d}s(1-s)^{\alpha -1}\varphi _{2}(s)\,ds>0\).
- \((\textbf{H}_{5})\):
-
$$ \lim_{x\rightarrow +\infty}\frac{h_{2}(x)}{x}=+\infty . $$
In view of \((H_{5})\), we know that there exists \(M>0\) such that \(h_{2}(x)\geq x\) for any \(x>M\).
For convenience, we introduce the following notations:
where \(r\in (0, +\infty )\), and \(M_{1}\) and \(M_{2}\) are as in Lemma 2.6.
In the following proofs, we always choose \(r_{2}>\max \{M+1,r_{1}+1\}\).
Theorem 3.4
Let \((H_{1})\)–\((H_{5})\) hold. Then the boundary value problem (1.1) has at least two positive solutions, provided that
where \(\lambda ^{*}=\min \{\xi _{r_{1}}^{-1}r_{1}, \xi _{r_{3}}^{-1}r_{3}\}\).
Proof
For any \(x\in \partial \Omega _{r_{1}}\) and \(t\in (0,1)\), we have \(\Vert x \Vert =r_{1}\) and
Then it follows from (3.5) that
Therefore \(\Vert Tx\Vert <\Vert x\Vert \).
On the other hand, for any \(x\in \partial \Omega _{r_{2}}\) and \(t\in (0,1)\), we have \(\Vert x \Vert =r_{2}\) and
From \((H_{2})\), \((H_{4})\), and \((H_{5})\) we obtain that
Therefore \(\Vert Tx\Vert >\Vert x\Vert \).
Then for any \(x\in \partial \Omega _{r_{3}}\) and \(t\in (0,1)\), we have \(\Vert x \Vert =r_{3}\) and
Therefore
Therefore \(\Vert Tx\Vert <\Vert x\Vert \).
Then it follows from Lemma 2.8 that T has at least two fixed points \(\tilde{x}_{1}\in K\cap (\Omega _{r_{2}}\backslash \Omega _{r_{1}})\) and \(\tilde{x}_{2}\in K\cap (\Omega _{r_{3}}\backslash \Omega _{r_{2}})\), that is, \(r_{1}<\Vert \tilde{x}_{1}\Vert <r_{2}<\Vert \tilde{x}_{2} \Vert <r_{3}\). Then we have
By Lemma 3.3 we know that \(x_{1}(t)=\tilde{x}_{1}(t)-\omega (t)+\bar{\eta}(t)\) and \(x_{2}(t)=\tilde{x}_{2}(t)-\omega (t)+\bar{\eta}(t)\) are two positive solutions of equation (1.1). The proof is completed. □
Theorem 3.5
Let \((H_{1})\)–\((H_{4})\) hold. Then the boundary value problem (1.1) has at least one nontrivial solution when \(\lambda <\xi _{r}^{-1}r\), where \(r>\max \{\frac{4cM_{2}}{M_{1}}, b\}\).
Proof
It is easy to show that exists r that satisfies
Then we can choose \(n_{0}\in \{1,2,\dots \}\) such that
For \(n\geq n_{0}\), we consider the family of integral equations
where
Let \(\Omega =\Omega _{r}=\{x\in K, \Vert x\Vert < r\}\). Then by the extension theorem of a completely continuous operator and the proof of Lemma 3.2 we get that \(T_{n}:K\cap \bar{\Omega}\rightarrow K\) is a completely continuous operator.
We consider the following operator equation:
that is,
where \(\kappa \in (0,1)\).
Then we will show that if \(x(t)\) is a solution of (3.11) for \(\kappa \in (0,1)\), then it satisfies \(\Vert x\Vert \neq r\).
Contrarily, if there exists \(\kappa \in (0,1)\) such that \(\Vert x\Vert =r\), then from (3.1) we have
and
By (3.2) we get
Therefore \(x^{*}(s-\tau )\geq \frac{1}{n}\) when n is sufficiently large.
Then by (3.12) we have
and, similarly to (3.4), we have
Then
This is a contradiction to \(\Vert x\Vert = r\), and then equation \(x=\kappa T_{n}x+(1-\kappa )\frac{1}{n}\) has no solution on \(x\in \partial (K\cap \Omega )\).
Therefore by the Lemma 2.9 we get that \(T_{n}\) have fixed points \(x_{n}\) in \(K\cap \bar{\Omega}\), that is,
and \(\Vert x_{n}\Vert \leq r\). Thus \(\{x_{n}\}\) is a uniformly bounded set on \((0,1)\).
By \((H_{2})\), \((H_{4})\), and Lemma 2.6 we have
and so \(x_{n}(t)\) has a lower bound.
Next, we will prove \(\{x_{n}\}\) is an equicontinuous set on \((0,1)\).
Since G is uniformly continuous for \(t\in [0,1]\), for any \(\varepsilon >0\), there exists \(\delta >0\) such that for \(t_{1}, t_{2}, s\in [0,1]\), if \(| t_{1}-t_{2}| <\delta \), then
and
Therefore \(\{x_{n}\}\) is an equicontinuous set on \((0,1)\), and then by the Arzelà–Ascoli theorem we get that \(\{x_{n}\}\) is a sequentially compact set and has a subsequence \(\{x_{n_{k}}\}\) (\(n_{k}\geq n\)) uniformly convergent to \(\tilde{x}\in K\cap \bar{\Omega}\), where
By the Lebesgue dominated convergence theorem we get
Therefore x̃ is a fixed point of T, and then \(x(t)=\tilde{x}(t)-\omega (t)+\bar{\eta}(t)\) is a nontrivial solution of (1.1). The proof is completed. □
Remark 3.6
Inequality (3.9) can be derived from the following condition:
- \((H_{6})\):
-
$$ \lim_{x\rightarrow +\infty}\frac{h_{1}(x)}{x}< \frac{1}{\lambda M_{2}\int _{\tau}^{1}s(1-s)^{\alpha -1}\varphi _{1}(s)\,ds}. $$
Corollary 3.7
Let \((H_{1})\)–\((H_{6})\) hold. Then the boundary value problem (1.1) has at least three nontrivial solutions.
Proof
Choose \(r=r_{1}\) in Theorem 3.5. Then it follows from Theorems 3.4 and 3.5 that the boundary value problem (1.1) has at least three nontrivial solutions. The proof is completed. □
Availability of data and materials
Not applicable.
Code availability
Not applicable.
References
Ardjouni, A.: Existence and uniqueness of positive solutions for nonlinear Caputo–Hadamard fractional differential equations. Proyecciones 40(1), 139–152 (2021)
Cabada, A., Hamdi, Z.: Existence results for nonlinear fractional Dirichlet problems on the right side of the first eigenvalue. Georgian Math. J. 24(1), 41–53 (2017)
Cabada, A., Wanassi, O.K.: Existence and uniqueness of positive solutions for nonlinear fractional mixed problems. Georgian Math. J. 28(6), 843–858 (2021)
Cui, Z., Zhou, Z.: Existence of solutions for Caputo fractional delay differential equations with nonlocal and integral boundary conditions. Fixed Point Theory Algorithms Sci. Eng. 2023(1), 1 (2023)
Granas, A., Dugundji, J.: Fixed Point Theory, vol. 14. Springer, Berlin (2003)
Gu, G., Yang, Z.: On the singularly perturbation fractional Kirchhoff equations: critical case. Adv. Nonlinear Anal. 11(1), 1097–1116 (2022)
Guo, D., Lakshmikantham, V.: Nonlinear Problems in Abstract Cones, vol. 5. Academic Press, San Diego (2014)
Henderson, J., Luca, R.: Existence of positive solutions for a singular fractional boundary value problem. Nonlinear Anal., Model. Control 22(1), 99–114 (2017)
Kilbas, A., Srivastava, H.M., Trujillo, J.J.: Theory and Applications of Fractional Differential Equations, vol. 204. Elsevier, Amsterdam (2006)
Liu, D., Zhang, K., Zhang, K.: Existence of positive solutions to a boundary value problem for a delayed singular high order fractional differential equation with sign-changing nonlinearity. J. Appl. Anal. Comput. 10(3), 1073–1093 (2020)
Luca, R.: On a class of nonlinear singular Riemann–Liouville fractional differential equations. Results Math. 73(3), 125 (2018)
Mu, Y., Sun, L., Han, Z.: Singular boundary value problems of fractional differential equations with changing sign nonlinearity and parameter. Bound. Value Probl. 2016, 1 (2016)
Podlubny, I.: Fractional Differential Equations: An Introduction to Fractional Derivatives, Fractional Differential Equations, to Methods of Their Solution and Some of Their Applications. Elsevier, Amsterdam (1998)
Su, X.: Positive solutions to singular boundary value problems for fractional functional differential equations with changing sign nonlinearity. Comput. Math. Appl. 64, 3425–3435 (2012)
Wang, Y.: Existence and multiplicity of positive solutions for a class of singular fractional nonlocal boundary value problems. Bound. Value Probl. 2019(1), 1 (2019)
Wang, Y.: Necessary conditions for the existence of positive solutions to fractional boundary value problems at resonance. Appl. Math. Lett. 97, 34–40 (2019)
Wang, Y.: The Green’s function of a class of two-term fractional differential equation boundary value problem and its applications. Adv. Differ. Equ. 2020(1), 1 (2020)
Wang, Y., Liu, L.: Positive properties of the Green function for two-term fractional differential equations and its application. J. Nonlinear Sci. Appl. 10(4), 2094–2102 (2017)
Xu, X., Zhang, H.: Multiple positive solutions to singular positone and semipositone m-point boundary value problems of nonlinear fractional differential equations. Bound. Value Probl. 2018(1), 1 (2018)
Zhang, W., Ni, J.: New multiple positive solutions for Hadamard-type fractional differential equations with nonlocal conditions on an infinite interval. Appl. Math. Lett. 118, 107165 (2021)
Zhao, K.: Triple positive solutions for two classes of delayed nonlinear fractional FDEs with nonlinear integral boundary value conditions. Bound. Value Probl. 2015(1), 1 (2015)
Zhao, X., Li, H., Yan, W.: Sobolev regularity solutions for a class of singular quasilinear ODEs. Adv. Nonlinear Anal. 11(1), 620–635 (2022)
Acknowledgements
This work was supported by National Natural Science Foundation of China (No. 62073186), Taishan Scholar Project of Shandong Province of China, and the NSF of Shandong Province ZR2021MA097.
Funding
This work was supported by National Natural Science Foundation of China (No. 62073186), Taishan Scholar Project of Shandong Province of China, and the NSF of Shandong Province ZR2021MA097.
Author information
Authors and Affiliations
Contributions
Rulan Bai, Kemei Zhang and Xue-Jun Xie wrote the main manuscript text. All authors reviewed the manuscript.
Corresponding author
Ethics declarations
Ethics approval and consent to participate
Not applicable.
Consent for publication
Not applicable.
Competing interests
The authors declare no competing interests.
Additional information
Publisher’s Note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Rights and permissions
Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.
About this article
Cite this article
Bai, R., Zhang, K. & Xie, XJ. Existence and multiplicity of solutions for boundary value problem of singular two-term fractional differential equation with delay and sign-changing nonlinearity. Bound Value Probl 2023, 114 (2023). https://doi.org/10.1186/s13661-023-01803-5
Received:
Accepted:
Published:
DOI: https://doi.org/10.1186/s13661-023-01803-5