NEW DELHI (AP) — When the Duke and Duchess of Cambridge arrive in India on what's being called their most ambitious tour to date, they'll encounter starry-eyed giddiness along with a hint of nostalgia harkening to a 1992 visit by Princess Diana. Prince William's mother created a firestorm of attention when she posed alone in front of the Taj Mahal, the marble mausoleum known as a monument to love because it was built by a Mughal emperor to entomb his beloved wife. "Royal visits improve atmospherics, leading to better political and economic ties," said former Indian Ambassador to Germany and France, T.C.A.