- decision problems,
- links between group theory and formal language theory,
- the theory of automatic groups and group combings,
- the language theoretical complexity of the word problem,
- the theoretical and practical development of algorithms in group theory.
- Susan Hermiller, Derek Holt, Sarah Rees and Tim Susse, Automaticity for graphs of groups, to appear in Geometry, Groups and Dynamics.
- Derek Holt, and Sarah Rees, Biautomatic structures in systolic Artin groups, to appear in Int. J. Algebra and Computation.
- Laura Ciobanu, Derek Holt, and Sarah Rees, Equations in groups that are virtually direct products, J. Algebra 516 (2018) 149--171.
- Patrick Dehornoy, Derek F. Holt and Sarah Rees, Multifraction reduction IV: Padding and Artin-Tits monoids of sufficiently large type , J. Pure and Applied Algebra 222 (2018) 4082--4098.
- Laura Ciobanu, Derek Holt, and Sarah Rees, The generalised word problem in hyperbolic and relatively hyperbolic groups, J. Algebra 516 (2018) 149--171.
- Gabriele Nebe, Richard Parker and Sarah Rees, A method for building permutation representations of finitely presented groups, in Proceedings of Finite Simple Groups: Thirty Years of the Atlas and Beyond, Princeton 2015.
- Derek F. Holt and Sarah Rees, Some closure results for C-approximable groups, Pac. J. Math. 287-2 (2017) 393--409.
- Eddy Godelle and Sarah Rees, Rewriting systems in sufficiently large Artin-Tits groups, J. Alg. 466 (2016) 284--307.
- Laura Ciobanu, Derek Holt and Sarah Rees, Rapid decay and Baum-Connes for large type Artin groups, TAMS 368 (2016) 6103--6129.
- My review of the film The Imitation Game, which appeared in the Newsletter of the Association for Women in Mathematics (AWM), March-April 2015, 17--19.
- Laura Ciobanu, Susan Hermiller, Derek Holt, and Sarah Rees, Conjugacy languages in groups, Israel J. Math. 211 (2015) 311--347.
- Derek F. Holt and Sarah Rees, Conjugacy in Artin groups of extra-large type, J. Alg. 434 (2015) 12--26.
- Laura Ciobanu, Derek Holt and Sarah Rees, Sofic groups: graph products and graphs of groups, Pac. J. Math. 271 (2014) 53--64.
- Mark Lawson, Liam O'Carroll and Sarah Rees, David Rees 1918-2013, Semigroup Forum 88 (2014) 513-522.
- Derek F. Holt and Sarah Rees, Shortlex automaticity and geodesic regularity in Artin groups, Groups, Complexity and Cryptology 5 (2013) 1--23.
- Laura Ciobanu, Derek F. Holt and Sarah Rees, Rapid Decay is Preserved by Graph Products, Journal of Topology and Analysis 5 (2013) 225--237.
- Derek F. Holt and Sarah Rees, Generalising some results about right-angled Artin groups to graph products of groups, Journal of Algebra 371 (2012) 94--104.
- Derek F. Holt and Sarah Rees,
Artin groups of large type are shortlex automatic with regular geodesics,
*Proc. London Math. Soc 104*(2012) 486--512. - Derek F. Holt, Sarah Rees, Claas E. Röver,
Groups with Context-Free Conjugacy Problems,
*Int. J. Alg. Comput. 21*(2011) 193-216. - Derek F. Holt, Sarah Rees and Michael Shapiro,
Groups that do and do not have growing context-sensitive word problem,
*Int. J. Alg. Comput. 18*(2008) 1179-1191. - Susan Hermiller, Derek Holt and Sarah Rees,
Groups whose geodesics are locally testable,
*Int. J. Alg. Comput.*18 (2008) 911-923. - Robert H. Gilman, Susan Hermiller, Derek F. Holt and Sarah Rees,
A characterisation of virtually free groups,
*Archiv der Math.*89 (2007) 289--295 - Sarah Rees,
The automata that define representations of monomial algebras,
*Algebras and Representation Theory*11 (2008) 207--214. - Oliver Payne and Sarah Rees,
Computing subgroup presentations using
the coherence arguments of McCammond and Wise,
*J. Alg.*300 (2006) 109--133 (Leedham-Green birthday volume). - Susan Hermiller, Derek Holt and Sarah Rees,
Star-free geodesic languages for groups,
*Int. J. Alg. Comp.*17 (2007) 329--345. - Michael Batty, Sam Braunstein, Andrew Duncan and Sarah Rees, Quantum algorithms in group theory, Computational and experimental group theory, 1--62, Contemp. Math., 349, Amer. Math. Soc., Providence, RI, 2004
- Derek F. Holt, Sarah E. Rees, Claas E Röver, and Richard M. Thomas, Groups with context-free co-word problem, Journal of the London Mathematical Society 71 (2005) 643-- 657.
- Sarah Rees, How hard is the word problem?, in Proceedings of Conference for European Women in Mathematics, Varna, Bulgaria, September 2002.
- Derek F. Holt and Sarah Rees, Regularity of quasigeodesics in a hyperbolic group,, Internat. J. Alg. Comp. 13 (2003) 585--596.
- Derek F. Holt and Sarah Rees,
Solving the word problem in real time,
*J. London Math. Soc.*63 (2001), 623--639. - George Havas, Derek F. Holt, P.E.Kenne and Sarah Rees,
Some challenging group presentations,
*J. Austral. Math. Soc.*67 (1999) 137--163. - Sarah Rees and Leonard H. Soicher,
An algorithmic approach to fundamental groups and
covers of combinatorial cell complexes,
*Symb. J. Comput.*29 (2000) 59--77. - Robert H. Gilman, Derek F. Holt and Sarah Rees,
Combing nilpotent and polycyclic groups,
*Inter. J. Alg. Comput.*9 (1999) 135--155. - Derek F. Holt and Sarah Rees,
Computing with abelian sections of finitely presented groups,
*J. Algebra*214 (1999) 714--728. - Sarah Rees,
Hairdressing in groups: a survey of combings and formal languages,
*Geometry and Topology Monographs*1 (1998), The Epstein Birthday Schrift, paper no. 24, pages 493-509. - Sarah Rees,
A language theoretic analysis of combings,
*Contemp. Math.*250, 117--136 - Sarah Rees,
Automatic groups associated with word orders other than shortlex,
*Inter. J. Alg. Comput.*8 (1998), 575--598. *quotpic*, an interactive graphics package to compute and display quotients of a finitely present group, and*testisom*, which attempts to test for isomorphism between two finitely presented groups, both developed jointly with Derek Holt, and available from the Warwick mathematics ftp-archive. as a joint package*isom_quotpic*.- automata,
a suite of programs, developed with David Epstein
and Derek Holt, to constructively
verify that a finitely presented group is shortlex automatic. Now superceded
by Derek Holt's
*kbmag*package, which is available from the Warwick mathematics ftp-archive. and contains my own code to test for automaticity with respect to other word orders than shortlex. *matrix group algorithms*developed jointly with Derek Holt, Charles Leedham-Green and Eamonn O'Brien, and now part of the matrix package within the GAP system- I have contributed to the magnus system, developed by the New York Group Theory Cooperative
- Authenticated password access to Newcastle University facilities.
- My link (with password access) to canvas in Newcastle; all my material for my lecture courses is available here.
- My personal link to Ness (student marks), which has access only by password.
- Classlists for courses at Newcastle, (access only by password).
- My link to Newcastle University library. The search facility in on this page, and from that I have password access to MathSciNet, JCR, and journals to which Newcastle has electronic access.
- Newcastle's page about videoconferencing
- Newcastle's Remote application Service.
- Password access to Newcastle's e-Portfolio system.
- Password access to Newcastle's staff home page.
- Password access to Newcastle's MyImpact system.
- Password access to Newcastle's MyApps system.
- School Calendars.
- A record of School Staff Leave.
- Newcastle forms to be filled out when I am away on business.
- Certain Newcastle web requisition system forms (that is, the ones relating to travel; these should cover everything I need to book).
- School wiki, which also has access only by password.
- Newcastle myworkplace, useful for expenses claims, which also has access only by password.
- Secure entry to the the outlook e-mail service in Newcastle.
- the Newcastle lunch run.
- the North British Geometric Group Theory Seminar .
- info on the Groups Breakout Session at the BMC in Glasgow, that was scheduled for April 2020. The 2020 BMC and the Groups Breakout Session have now been postponed until 2021, due to the coronavirus crisis.
- the EPSRC's useful list of its grants on the web
- two lists of journals considered by Newcastle Research Committee to represent 3-star and 4-star quality. Essentially these lists are extracted from a list of journals ranked by 5yr impact factor.
- the arxiv
- home page for the Magic consortium of UK universities, of which Newcastle is a member, which uses distance learning techniques to supply lecture courses to educate postgraduate students in mathematics and statistics.
- home page for the London Taught Course Centre (LTCC) , which provides lecture courses for postgraduate students from a consortium of universities in an around London.

## Office hours for Newcastle studentsNormally I have regular office hours in term time for students in the modules I lead, when I am happy to see students without appointment, in my office 3.07 (Herschel building).Currently, due to the Covid-19 crisis, office hours are via zoom, and in semester 2 they are Mondays on 1530-1700, Thursdays 1030-1130. (Note that on Thursdays they are an hour later than they were in semester 1). On Monday 22ndth March, I will run my Monday office hours only from 1715 to 1800, due to a clash. The zoom link is within my course pages (in 2020/21 for MAS3710 and MAS2706) on Canvas; MAS3710 or MAS2706 students who want to see me should follow that link for password free access, I'd be happy to email the link to anyone who wants to see me who's not in that module. Students are also welcome to consult me by email, using the address above. I check email regularly, and will respond to all emails as quickly as possible.
## Research InterestsI work mainly on geometrical, combinatorial and computational aspects of group theory. In particular I am currently interested in
## My bookMy book, Groups Languages and Automata, authors Derek F. Holt, Sarah Rees, Claas E. Röver, was published by CUP in February 2017, as volume 88 of the London Mathematical Society student texts series. We three authors are maintaining a list of errors and misprints in our book as we discover them; so please let one of us know (e.g. by e-mail) if you find any problems that are not in that list.## Electronic copies of articles from 1998 onwards
## Computer packages## Useful links## within Newcastle:-(some of these are really for my personal use, others are for students) ## and outside Newcastle:- |