Me and my friend in initial stages of our PhD worked on same research problems in theoretical computer science (TCS) under the same supervisor. Is it ethically acceptable in TCS community to have almost identical (50%) dissertations containing identical chapters?

Note: This question was originally asked here.

  • 1
    Unrelated to the field but I think it's important to emphasize that, unless really well explained in both your theses, one could see a case of plagiarism without having full knowledge of the context. If your university has an anti plagiarism tool, then you might want to agree with your friend to (1) write your own dissertations and (2) make sure that both your theses are checked for plagiarism to prevent for honest mistakes.
    – PatW
    Feb 6, 2016 at 8:49
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    I do not understand. You published some common papers. How many? One, two, more than two? Then you probably have to decide (with your advisor) which of those papers go to the PHD thesis of whom. You cannot put all the same papers (when they are many) on both theses.
    – Alexandros
    Feb 6, 2016 at 9:04
  • A side note: it would have been better if you had flagged the original question for migration. Feb 6, 2016 at 12:43
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    @Alexandros, why not?
    – usul
    Feb 6, 2016 at 13:51
  • @usul Your thesis should demonstrate that you have made an original contribution to your subject. Consider the extreme case where they two theses end up identical. Who did the work? At the very least I would expect an explanation of what your contribution was. But if you really are doing everything equally, you should between you still produce enough for two theses.
    – Jessica B
    Feb 10, 2016 at 8:14

1 Answer 1


The correct answer is always to check you local (faculty) rules for theses.

I'm not from TCS, but here are my 2 ct: If the same chapters are actually papers in a staple (cumulative) thesis, that is acceptable over here (the papers will appear as their print version in cumulative theses). We have rules that establish a point system depending on who is first and who is second author.

Here's an example: student T focuses more on theory and student A on an application (or maybe for TCS, on simulation?). Then 2 papers (not LPUs) are written, one focusing on theory with short application example with T 1st author and A 2nd author; the other paper discussing the application in detail and just briefly the theory. Here authorship is the other way round. Both students can take both papers into their theses, and each gains 1.5 publication points. If, say, the application example isn't worth a full paper, then only 1 paper is written and T gains 1 point, while S gains only 0.5 points (not being the first author). Both put the complete paper into their thesis.

In any case, the non-stapled parts of the theses need to be different in order to establish who did what part of the work, because the degree is given for the own work of each student. So if all work was done as team work, there will probably be trouble because the committee cannot know how to assign grades to whom.

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    TCS doesn't have "first" authors, and our papers tend to be a mixture of theory, theory, and theory.
    – JeffE
    Feb 6, 2016 at 15:10
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    @JeffE The separation between theory and application was just "an example". There is presumably some difference in emphasis between the two students, and some portions of the combined work that each considers to be their contribution. Feb 6, 2016 at 15:29

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