Hagahot notes the appearance of a new study by two Tel Aviv University scholars, Arye Edrei and Doron Mendels, "A Split Jewish Diaspora: Its Dramatic Consequences," Journal for the Study of the Pseudepigrapha 16:2 (2007): 91-137, wherein the authors demonstrate
that the Jewish diaspora in Europe basically disappeared after the destruction of the Second Temple. Probably, they felt cut off from the spiritual center in Jerusalem, and eventually melded into their host culture.For those interested, the abstract of this article reads:
This is very significant for medieval Jewish history, especially those interested in the roots of Ashkenazic halakhah. The Jewish settlement along the Rhine identified itself as being rooted in Northern Italy, and when it first surfaces in literary form, the Ashkenazic halakhah is already a hoary tradition. On the other hand, while we have extensive epigraphical remains from the Jews of Roman Italy, they don't reflect what we know about rabbinic Judaism. So this theory suggests that there was a break between Roman Italy and early medieval Italy, with the later Jewish population coming from a totally different, more rabbinic culture.
This article proposes that a language divide and two systems of communication have brought to a serious gap between the western Jewish Diaspora and the eastern one. Thus the western Greek-speaking Jews lost touch with the Halakhah and the Rabbis, a condition that had far-reaching consequences on Jewish history thereafter. The Rabbis paid a high price for keeping their Halakhah in oral form, losing in consequence half of their constituency. An oral law did not develop in the western diaspora, whereas the existing eastern one was not translated into Greek. Hence it is not surprising that western Jews contributed nothing to the development of the oral law in the east. The Jewish communities that were isolated from the Rabbinic network served as a receptive basis for the development of an alternative Christian network by Paul and the apostles, which enabled it to spread throughout the Mediterranean basin. The Jews that remained ‘biblical’ surfaced in Europe in the Middle Ages.