Comments Regarding A Successful Defense Of A Dissertation (Input from a 2007 Physics Alum)

In 2007, Willie Merrell, a theoretical particle physics student from PROMISE at College Park, shared the following information following his doctoral defense. Willie was part of the first group of PROMISE Peer Mentors. We reprise this article which has been used as a handout for the Dissertation House, and hope that it will assist a wide range of students.


In my experience from watching dissertation defenses and from defending my own dissertation, I have observed that there are three important components to any successful defense. These components are:

1. The Presentation

2. The Original Work

3. Your Work in Context

Here are some tips I’ve learned for performing well on each component.

1)      The Presentation

This area is sometimes overlooked because it is viewed as superficial, especially when compared to the actual work that is being judged. However, just as in dating, presentation matters. In a defense, one can’t get by just on a great looking presentation, but it can help in getting the relevant information across and in eliminating unwanted questions arising from simple misunderstandings.

The key parts to having a good presentation are:

a)      Making the presentation readable. Make sure that relevant characters can be seen.

b)      Using a clear and consistent labeling scheme. Make sure that your variables, and names are used to mean only one thing. If there is community accepted double use for a label, make sure that you give a explanation of that convention.

c)       Having a clear organization. As much as possible you would like the ideas and results that you present to follow a logical and pedagogical progression of thought. A lot of questions come from this component for the simple fact that not everyone thinks alike. Sometimes, committee members will ask these types of questions just to see how well you have thought about the logic of your work. Examples are very helpful in explaining concepts. Wherever possible, use simple examples that capture the essence of the point you are trying to make.  Examples are nice in that, if you are running out of time they can be easily skipped.

d)      Eliminating distracting content. Since there are often many different and independent components of the work, multiple colors and animations are often used to help distinguish these pieces. However, one should not add something just because it looks nice. Such things tend to distract people and can introduce confusion when they expect the added fluff to be meaningful. It can be very embarrassing to have to admit that something you put in the presentation had no real value.

e)      Clearly point out your original contribution. This is not the time to be modest. Let everyone in the room know what you claim as your work with pride (But make sure you leave your arrogance at home.)

2)      The Original Work

This is your baby. You own this. You have done the research, the analysis, the implementation. You should have complete mastery over this part. That is the first reason for the defense. It is time to show others that you have mastered your work. Expect them to attack anything and everything just to see if there is a weakness in your understanding. This might seem like a daunting challenge but remember that the committee knows you are only human. There will be some things that you don’t know and that is o.k. Knowing the depths of the foundations of the principles used in your research is a lifelong challenge. For this component you want to keep two things in mind.

a)      What you want to do is make sure that you have a reasonable understanding of the principles that you have used in your work. You are expected to get the community standard concepts right. You get extra credit for understanding the strengths, the flaws, and the hidden assumptions used in your techniques and procedures and how they relate to other techniques and procedures that you didn’t use.

b)      There is a reason it is called a defense. Be prepared to defend your work and the choices made in your analysis, and procedures. It may sound like a lot but remember that you have already done most of this work when you were learning about the foundations of your research. This is where you want to go back and make sure you understand as many of those things as you can for which you said “I’ll figure it out later.”

3)       Your Work in Context

As a Ph.D.,  you are expected to have some idea of where your work fits in the broad view of your academic area and how your work relates to the work of others. Since this amount of work done by others is very large, focus on learning works directly related your work to a degree that is reasonable for your workload. Don’t be afraid of questions about works with which you are not familiar. There is a strategy for dealing with such questions. The point of the question is about how the other work relates to your work. Ask questions to find the perceived link between your work and other work referenced and comment about that link based the goals of your work and the constraints under which your work was performed. Try to be specific, but concise, about the reasons you have for the perspective you give. This will effectively demonstrate that you understand how to place your work in context as you encounter other works and expand your own work.


About the author:

Willie Merrell completed his PhD in Physics at the University of Maryland College Park.  Following receipt of the doctorate, he joined the String Theory Group at the University of Kentucky as a Lyman T. Johnson Postdoctoral Fellow. His work in supersymmetry can be summarized as follows:  

Supersymmetry is a symmetry that relates bosonic and fermionic states of a theory. It is a great theoretical tool for performing calculations that are otherwise intractable. The use of supersymmetry is also a leading candidate for solving a major theoretical problems with the standard model of particle physics, the hierarchy problem, and is a necessary part of superstring theory. His research involves using the natural mathematical language for supersymmetry, i.e. Superspace, to aid in formulating supersymmetric theories and performing calculations in supersymmetric systems relevant to superstring theory and supersymmetric field theory.

Dr. Merrell is now a scientist at NASA.

Photos of nebulae courtesy of
National Space Science Data Center


This post may be copied, but please reference “The Dissertation House —, a program of PROMISE: Maryland’s AGEP.”


The text content of this post was compiled and written by the staff of PROMISE: Maryland’s AGEP and may not be copied without referencing the PROMISE organization, as “PROMISE: Maryland’s AGEP”.

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About Renetta Garrison Tull

Dr. Renetta Garrison Tull is the Vice Chancellor for Diversity, Equity, and Inclusion (DEI) at the University of California Davis. She previously served as Associate Vice Provost for Strategic Initiatives at The Graduate School at UMBC, and was Professor of the Practice in the College of Engineering & IT. She was Special Assistant to the Sr. Vice Chancellor for Academic Affairs & Director of Graduate and Professional Pipeline Development for the University System of Maryland (12 institutions). She is the Founding Director of PROMISE: Maryland’s Alliance for Graduate Education and the Professoriate (AGEP) –, and Co-PI for the USM LSAMP. Her research on global diversity in STEM continues, and she is an international speaker, covering nearly all continents, for groups and conferences such as the World Engineering Education Forum, the International Federation of Engineering Education Societies, and the Pacific Sciences Congress. Her personal website is: Connect with her on Twitter: @Renetta_Tull;
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1 Response to Comments Regarding A Successful Defense Of A Dissertation (Input from a 2007 Physics Alum)

  1. I love these comments, particularly the statements about positioning your own work within the broader disciplinary context, and about not knowing everything. “There will be some things that you don’t know and that is o.k.” – even after just having defended, this is a welcome confirmation that I will be repeating to myself during the revisions.

    Thank you, Dr. Merrell and PROMISE

    – Alexis

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