Let s ∈ R , τ ∈ [ 0 , ∞ ) , p ∈ ( 1 , ∞ ) and q ∈ ( 1 , ∞ ] . In this paper, we introduce a new class of function spaces F ˙ p , q s , τ ( R n ) which unify and generalize the Triebel–Lizorkin spaces with both p ∈ ( 1 , ∞ ) and p = ∞ and Q spaces. By establishing the Carleson measure characterization of Q space, we then determine the relationship between Triebel–Lizorkin spaces and Q spaces, which answers a question posed by Dafni and Xiao in [G. Dafni, J. Xiao, Some new tent spaces and duality theorem for fractional Carleson measures and Q α ( R n ) , J. Funct. Anal. 208 (2004) 377–422]. Moreover, via the Hausdorff capacity, we introduce a new class of tent spaces F T ˙ p , q s , τ ( R + n + 1 ) and determine their dual spaces F W ˙ p ′ , q ′ − s , τ / q ( R n ) , where s ∈ R , p , q ∈ [ 1 , ∞ ) , max { p , q } > 1 , τ ∈ [ 0 , q ( max { p , q } ) ′ ] , and t ′ denotes the conjugate index of t ∈ ( 1 , ∞ ) ; as an application of this, we further introduce certain Hardy–Hausdorff spaces F H ˙ p , q s , τ ( R n ) and prove that the dual space of F H ˙ p , q s , τ ( R n ) is just F ˙ p ′ , q ′ − s , τ / q ( R n ) when p , q ∈ ( 1 , ∞ ) .
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