1 9 3 0 s , ▁On s ager ▁research ed ▁the ▁di pole ▁theory ▁of ▁die lect rics , ▁making ▁improvements ▁for ▁another ▁topic ▁that ▁had ▁been ▁studied ▁by ▁Peter ▁Deb ye . ▁However , ▁when ▁he ▁submitted ▁his ▁paper ▁to ▁a ▁journal ▁that ▁Deb ye ▁edited ▁in ▁ 1 9 3 6 , ▁it ▁was ▁rejected . ▁Deb ye ▁would ▁not ▁accept ▁On s ager ' s ▁ideas ▁until ▁after ▁World ▁War ▁II . ▁During ▁the ▁ 1 9 4 0 s , ▁On s ager ▁studied ▁the ▁statistical - me chan ical ▁theory ▁of ▁phase ▁trans itions ▁in ▁sol ids , ▁der iving ▁a ▁mathemat ically ▁elegant ▁theory ▁which ▁was ▁enthus iast ically ▁received . ▁In ▁what ▁is ▁widely ▁considered ▁a ▁tour ▁de ▁force ▁of ▁mathematical ▁physics , ▁he ▁obtained ▁the ▁exact ▁solution ▁for ▁the ▁two ▁dimensional ▁Is ing ▁model ▁in ▁zero ▁field ▁in ▁ 1 9 4 4 . ▁ ▁In ▁ 1 9 6 0 ▁he ▁was ▁awarded ▁an ▁honor ary ▁degree , ▁doctor ▁techn . ▁honor is ▁causa , ▁at ▁the ▁Norwegian ▁Institute ▁of ▁Technology , ▁later ▁part ▁of ▁Norwegian ▁University ▁of ▁Science ▁and ▁Technology . ▁ ▁In ▁ 1 9 4 5 , ▁On s ager ▁was ▁natural ized ▁as ▁an ▁American ▁citiz en , ▁and ▁the ▁same ▁year ▁he ▁was ▁awarded ▁the ▁title ▁of ▁J . ▁Will ard ▁Gib bs ▁Professor ▁of ▁The oret ical ▁Chem istry . ▁This ▁was ▁particularly ▁appropriate ▁because ▁On s ager , ▁like ▁Will ard ▁Gib bs , ▁had ▁been