Twenty-three mats were back in action today at the FargoDome in Fargo, N.D. as 984 freestyle wrestlers kicked off the second half of the Advocare Cadet National Championships.    Several big names highlighted today's wrestling as returning champions and 2001 Greco-Roman champions showed why they've won the gold before.    Heavyweight Patrick Barrentine of Ohio, fresh off his Cadet National Greco-Roman Championship on Monday night, continued his dominance, winning both of his matches today by technical fall, 11-1 and 15-3.    Grant Miller (209) of Illinois, who stood on the gold medal stand with Barrentine on Monday, didn't allow a point today en route to two victories; one an 11-0 technical fall and the other a pin in 24 seconds.     Eric Tannenbaum (132) of Illinois, Outstanding Wrestler and champion from the Greco-Roman finals, didn't have it quite as easy as his fellow champions.     While he breezed through his first two matches with 10-0 and 11-0 technical fall victories, he met quite a challenge in his third match against Jeff Jaggers (132) of Ohio. He squeaked by in the end, though, scoring a 3-2 victory for his third victory of the day. He took his fourth and final match by a score of 9-6.     Returning champion Charlie Falck (103.5) of Minnesota also had problems today. After scoring a 10-0 technical fall in his first bout, he narrowly made it by Micah Ferguson (103.5) of California 3-2 to finish 2-0 on the day.    Action picks up Thursday morning as the Cadets continue their run for gold, while the Juniors will kick off the first round of the Asics Junior National Championships.