The Mishna [Kiddushin 2a] establishes that death of the husband breaks the bond between man and wife. What is the nature of this break? Is it an active dissolution of the marriage or is it just that the husband is gone so automatically she is husband-less and free to marry someone else. In the terminology of the Heilige Rogochover is מיתה a פעולה or העדר. A possible nafka minah - If the husband comes back to life, does he need to remarry her or are they automatically back together. If it is an active פעולה they would need to remarry. If it is just that he disappeared in the meantime - נעדר - if he comes back to life they would be right back together.
The Acharonim have quite a bit of discussion on the topic [here is one article and yet another]. The Rogochover wasn't terribly interested in Achronim and he found most things in the Gemara-Rashi-Tosfos-Rambam. He noted that the two sides of the chakira are reflected in the two answers the Gemara [Kiddushin 2b] gives to the question וניתני האיש קונה ומקנה - Why does the Mishna not say האיש קונה a man acquires [instead of האשה נקנית] and האיש מקנה [instead of וקונה את עצמה]. Why do we couch the law in terms of the woman [who is passive] and not the man [who is doing the marrying and divorcing].
The Gemara's first answer is that a man is not מקנה ["freeing"] a woman when he dies. It is Hashem who is doing the הקנאה. In the Gemara's words מן שמיא הוא דמקני לה. This means that a husband isn't actively causing the woman to be unmarried but rather he was taken away by Divine will and therefore he is no longer around to make her forbidden to others. This answer takes the position that death is העדרand not an active dissolution.
The second answer is that if it would have said קונה I would have assumed that this means even against her will - by saying נקנית we understand that the woman must agree to the marriage [no forced marriages by yidden...]. This answer rejects the premise of the first answer [that it is a Divine act] but rather it is the husband who is freeing her [i.e. it is his פעולה]. This is like the first side of the chakirah we presented.
In his not-normal geonus, the Rogochover marshals more proofs which I hope to get to in future posts....:-).
לזכות נעכא גיטל בת רחל אסתר זרעא חייא וקיימא זרעא די לא יפסוק ודי לא יבטול מפתגמי אורייתא