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Abstract

We derive sufficient conditions for two integral operators to be convex (univalent) provided that the factors are 𝛽-spirallike

Results & Lemmas (7)

Each result is auto-extracted from the paper via OCR - the math is shown verbatim and may carry occasional transcription artifacts. Click to expand the full statement.

Lemma 1. Lemma 1. 𝑓(𝑧) is 𝛽-spirallike if and only if there is a starlike function 𝑠(𝑧),such that 𝑓(𝑧) 𝑧 = (𝑠(𝑧) 𝑧) 𝛼 (π‘§βˆˆπ‘ˆ), Where 𝛼= π‘’βˆ’π‘–π›½cos𝛽.
Lemma 1. 𝑓(𝑧) is 𝛽-spirallike if and only if there is a starlike function 𝑠(𝑧),such that 𝑓(𝑧) 𝑧 = (𝑠(𝑧) 𝑧) 𝛼 (π‘§βˆˆπ‘ˆ), Where 𝛼= π‘’βˆ’π‘–π›½cos𝛽.
Theorem 1. Theorem 1. Let 𝐹𝑛(𝑧) be the integral operator given by (1), for π‘—βˆˆ 1,β‹…β‹…β‹…β‹…, 𝑛, if (i) 𝑓𝑗 is 𝛽-spirallike for every 𝑗,(βˆ’ πœ‹ 2 < 𝛽< πœ‹ 2). (ii)βˆ‘β€¦
Theorem 1. Let 𝐹𝑛(𝑧) be the integral operator given by (1), for π‘—βˆˆ{1,β‹…β‹…β‹…β‹…, 𝑛}, if (i) 𝑓𝑗 is 𝛽-spirallike for every 𝑗,(βˆ’ πœ‹ 2 < 𝛽< πœ‹ 2). (ii)βˆ‘ 1 cos𝛽𝑗 𝑛 𝑗=1 < 𝑛+ 1. (iii) 𝛼𝑗= 𝑒𝑖𝛽𝑗. Then 𝐹𝑛(𝑧) is convex.
Corollary 1. Corollary 1. Let 𝑓(𝑧) be 𝛽-spirallike,(βˆ’ πœ‹ 2 < 𝛽< πœ‹ 2), if (i)𝛼= 𝑒𝑖𝛽. (ii)cos𝛽> 𝑛 𝑛+1,(𝑛 is a positive integer). Then: βˆ«π‘‘ 𝑛((β„œπ›Ό)2+β„œπ›Όβˆ’1 β„œπ›Ό )…
Corollary 1. Let 𝑓(𝑧) be 𝛽-spirallike,(βˆ’ πœ‹ 2 < 𝛽< πœ‹ 2), if (i)𝛼= 𝑒𝑖𝛽. (ii)cos𝛽> 𝑛 𝑛+1,(𝑛 is a positive integer). Then: βˆ«π‘‘ 𝑛((β„œπ›Ό)2+β„œπ›Όβˆ’1 β„œπ›Ό ) (𝑓(𝑑)
Corollary 2 Corollary 2 Let 𝑓(𝑧) be 𝛽-spirallike,(βˆ’ πœ‹ 6 < 𝛽< πœ‹ 6), if 𝛼= 𝑒𝑖𝛽 Then: βˆ«π‘‘ (β„œπ›Ό)2+β„œπ›Όβˆ’1 β„œπ›Ό (𝑓(𝑑) 𝑑) 𝛼 𝑑𝑑 𝑧 0
Corollary 2 Let 𝑓(𝑧) be 𝛽-spirallike,(βˆ’ πœ‹ 6 < 𝛽< πœ‹ 6), if 𝛼= 𝑒𝑖𝛽 Then: βˆ«π‘‘ (β„œπ›Ό)2+β„œπ›Όβˆ’1 β„œπ›Ό (𝑓(𝑑) 𝑑) 𝛼 𝑑𝑑 𝑧 0
Theorem 2. Theorem 2. Let 𝐺𝑛(𝑧) be the integral operator given by (2), for π‘—βˆˆ 1,β‹…β‹…β‹…β‹…, 𝑛, if (i) 𝑓𝑗 is 𝛽-spirallike for every 𝑗,(βˆ’ πœ‹ 2 < 𝛽< πœ‹ 2). (ii)βˆ‘β€¦
Theorem 2. Let 𝐺𝑛(𝑧) be the integral operator given by (2), for π‘—βˆˆ{1,β‹…β‹…β‹…β‹…, 𝑛}, if (i) 𝑓𝑗 is 𝛽-spirallike for every 𝑗,(βˆ’ πœ‹ 2 < 𝛽< πœ‹ 2). (ii)βˆ‘ cos𝛽𝑗 𝑛 𝑗=1 < 1. (iii) 𝛼𝑗= 𝑒𝑖𝛽𝑗. Then 𝐺𝑛(𝑧) is convex.
Corollary 3. Corollary 3. Let 𝑓(𝑧) be 𝛽-spirallike,(βˆ’ πœ‹ 2 < 𝛽< πœ‹ 2), if (i)𝛼= 𝑒𝑖𝛽. (ii)cos𝛽< 1 𝑛,(𝑛 is a positive integer). Then: ∫(𝑓(𝑑) 𝑑) 𝑛𝛼 𝑑𝑑 𝑧
Corollary 3. Let 𝑓(𝑧) be 𝛽-spirallike,(βˆ’ πœ‹ 2 < 𝛽< πœ‹ 2), if (i)𝛼= 𝑒𝑖𝛽. (ii)cos𝛽< 1 𝑛,(𝑛 is a positive integer). Then: ∫(𝑓(𝑑) 𝑑) 𝑛𝛼 𝑑𝑑 𝑧
Corollary 4 Corollary 4 Let 𝑓(𝑧) be 𝛽-spirallike,(βˆ’ πœ‹ 2 < 𝛽< πœ‹ 2), if 𝛼= 𝑒𝑖𝛽 Then: ∫(𝑓(𝑑) 𝑑) 𝛼 𝑑𝑑 𝑧 0
Corollary 4 Let 𝑓(𝑧) be 𝛽-spirallike,(βˆ’ πœ‹ 2 < 𝛽< πœ‹ 2), if 𝛼= 𝑒𝑖𝛽 Then: ∫(𝑓(𝑑) 𝑑) 𝛼 𝑑𝑑 𝑧 0

Definitions (3)

Def 1. Definition 1. A function π‘“βˆˆπ‘ˆ is called 𝛽-spirallike if β„œ(𝑒𝑖𝛽𝑧𝑓′(𝑧) 𝑓(𝑧) ) > 0, (π‘§βˆˆπ‘ˆ) for a real number 𝛽(βˆ’ πœ‹ 2 < 𝛽< πœ‹ 2). Also we denote by…
Definition 1. A function π‘“βˆˆπ‘ˆ is called 𝛽-spirallike if β„œ(𝑒𝑖𝛽𝑧𝑓′(𝑧) 𝑓(𝑧) ) > 0, (π‘§βˆˆπ‘ˆ) for a real number 𝛽(βˆ’ πœ‹ 2 < 𝛽< πœ‹ 2). Also we denote by 𝐾 the class of convex functions in 𝐴 normalized by 𝑓(0) = 𝑓′(0) βˆ’1 = 0, and β„œ{𝑧𝑓′′(𝑧)
Def 2. Definition 2. Let 𝐹𝑛(𝑧) = βˆ«π‘‘ (β„œπ›Ό1)2+β„œπ›Ό1βˆ’1 β„œπ›Ό1 (𝑓1(𝑑) 𝑑 ) 𝛼1 ⋅⋅⋅⋅⋅𝑑 (β„œπ›Όπ‘›)2+β„œπ›Όπ‘›βˆ’1
Definition 2. Let 𝐹𝑛(𝑧) = βˆ«π‘‘ (β„œπ›Ό1)2+β„œπ›Ό1βˆ’1 β„œπ›Ό1 (𝑓1(𝑑) 𝑑 ) 𝛼1 ⋅⋅⋅⋅⋅𝑑 (β„œπ›Όπ‘›)2+β„œπ›Όπ‘›βˆ’1
Def 3. Definition 3. Let 𝐺𝑛(𝑧) = ∫(𝑓1(𝑑) 𝑑 ) 𝛼1 β‹…β‹…β‹…β‹…β‹…(𝑓𝑛(𝑑) 𝑑 ) 𝛼𝑛 𝑑𝑑
Definition 3. Let 𝐺𝑛(𝑧) = ∫(𝑓1(𝑑) 𝑑 ) 𝛼1 β‹…β‹…β‹…β‹…β‹…(𝑓𝑛(𝑑) 𝑑 ) 𝛼𝑛 𝑑𝑑
Function classes studied:

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