When the mind cease and breathing appear automatically ;means the experience of knower ?in which jhana the consciousness is expanding?
i think "knower" is a term used by contemporary meditation teachers especially if this "knower" is used in a context outside of 5 skandhas then it might be problematic. (tho not 100% sure, if anyone can provide pali for knower then i would look it up). Unless "knower" from your question means vinnana, consciousness. according to pali texts, mind temporary ceases (while still alive) at cessation meditation level. Mind still exists even at neither perception nor non-perception level.
from what i read, consciousness expands to infinite space at non-form perception (above 4th jhana). "the sphere of infinite space perception"..