Sharper Inequalities for Numerical Radius for Hilbert Space Operator

We give several sharp inequalities for the numerical radius of Hilbert space operators .It is shown that if A and B are bounded linear operators on complex Hilbert space H , then 1 2 1 2(1 ) 2(1 ) 2 2 2 2 1 ( ) 2 ( ) 2 r r r r r r w A B A B A B A B α α α α − − − ∗ ∗ ⎛ ⎞ + ≤ + + + + + ⎜ ⎟ ⎝ ⎠ , for 0<r 1 ≤ and ( ) 1 , 0 ∈ α , and if ( ) n A M ∈ , then 2 1 ( ) 4 w A ≤ ( ) 2 2 A A A A ∗ ∗ + + − , where (.) ω and . are the numerical radius and the usual operator norm, respectively. In addition, from the first inequality, we obtain sharp inequalities. Mathematics Subject Classification: 47A12, 47A30, 47A63