Would like to get expert advice regarding yoga to alleviate chronic lumbar pain.?

Yoga would be great. As long as you have had your chronic lumbar pain properly worked up, I am fine with yoga. Do your homework and find a yoga instruction that is familiar and has worked with low back patients. You must start at the beginner level and go slowly. Do not do painful poses and work within your range of movement. Remember when you first start, there could be muscle soreness. Go slow and easy will be fine.