On bilinear Hardy inequality and corresponding geometric mean inequality

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On bilinear Hardy inequality and corresponding geometric mean inequality Amiran Gogatishvili1

· Pankaj Jain2 · Saikat Kanjilal2

Received: 15 July 2020 / Accepted: 11 September 2020 © Università degli Studi di Napoli "Federico II" 2020

Abstract The main aim of this paper to provide several scales of equivalent conditions for the bilinear Hardy inequalities in the case 1 < q, p1 , p2 < ∞ with q ≥ max( p1 , p2 ). Keywords Hardy inequality · Bilinear Hardy inequality · Integral conditions · Equivalent conditions · Geometric mean inequality Mathematics Subject Classification 26D10 · 46E35

1 Introduction Let M denote the set of all Lebesgue measurable functions on (a, b), −∞ ≤ a < b ≤ ∞, M+ ⊂ M is the subset of all non-negative functions. p and write Let u, v, ∈ M+ , 0 < p, q ≤ ∞, p ≥ 1. Denote p  := p−1 

b

U (x) =

 u(t) dt, V (x) =

x

x



v 1− p (t) dt,

(1)

a

and assume that U (x) < ∞, V (x) < ∞ for almost everywhere (a.e.) x ∈ (a, b).

B

Amiran Gogatishvili [email protected] Pankaj Jain [email protected]; [email protected] Saikat Kanjilal [email protected]; [email protected]

1

Institute of Mathematics of the Czech Academy of Sciences, Žitná 25, 115 67 Prague 1, Czech Republic

2

Department of Mathematics, South Asian University, Chanakya Puri, New Delhi 110021, India

123

A. Gogatishvili et al.

Consider the one dimensional Hardy inequality 

b



a

x

q f (t) dt

 q1 u(x) d x



b

≤C

a

f (x)v(x) d x p

 1p

,

f ∈ M+ .

(2)

a

It is known that the inequality (2) is characterized by the Muckenhoupt condition [9] in the case 1 < p ≤ q < ∞ which is given by 1

A M := sup A M (x) = sup U q (x)V a