Apple up 5.4%, Samsung down 5%, since Galaxy S4 event by Philip Elmer-DeWitt @FortuneMagazine March 18, 2013, 8:35 PM EDT E-mail Tweet Facebook Google Plus Linkedin Share icons FORTUNE — Who would have guessed a week ago that the thing that would lift Apple AAPL out of its winter doldrums would be the unveiling of its fiercest competitor’s whizzy new flagship device? But that’s what happened. The day after Thursday evening’s big event at Radio City Music Hall — where Samsung introduced the Galaxy S4 in a faux-Broadway production that garnered mostly negative reviews — Apple opened $5.43 higher and closed up $11.16. Apple’s shares picked up Monday where they left off Friday, gaining another $12 to close at $455.72, up $5.4% over the two-day stretch. Samsung, meanwhile, has been moving in the opposite direction, down nearly 5% since Thursday’s close.