function gs_author_fb()
{
if ( is_single ) {
$authorfirst = get_the_author_meta('first_name');
$authorlast = get_the_author_meta('last_name');
echo  '<meta name="author" content="'. $authorfirst . " " . $authorlast .'" />';
}
}

add_action('wp_head','gs_author_fb');