Editing Random walk (section)

===Number of distinct sites===
The number of distinct sites visited by a single random walker <math>S(t)</math> has been studied extensively for square and cubic lattices and for fractals.<ref name="WeissRubin1982">{{cite book|last1=Weiss|first1=George H.|title=Advances in Chemical Physics|last2=Rubin|first2=Robert J.|chapter=Random Walks: Theory and Selected Applications|volume=52|year=1982| pages=363–505|doi=10.1002/9780470142769.ch5|isbn=978-0-470-14276-9}}</ref><ref name="BlumenKlafter1986">{{cite book| last1=Blumen|first1=A. |title=Optical Spectroscopy of Glasses|last2=Klafter|first2=J.|last3=Zumofen|first3=G.|chapter=Models for Reaction Dynamics in Glasses|volume=1|year=1986|pages=199–265|doi=10.1007/978-94-009-4650-7_5|bibcode = 1986PCMLD...1..199B | series=Physic and Chemistry of Materials with Low-Dimensional Structures|isbn=978-94-010-8566-3}}</ref> This quantity is useful for the analysis of problems of trapping and kinetic reactions. It is also related to the vibrational density of states,<ref name="AlexanderOrbach1982">{{cite journal|last1=Alexander|first1=S.|last2=Orbach|first2=R.|title=Density of states on fractals: " fractons "|journal=Journal de Physique Lettres|volume=43|issue=17|year=1982| pages=625–631| doi=10.1051/jphyslet:019820043017062500 |s2cid=67757791|url=https://hal.archives-ouvertes.fr/jpa-00232103/file/ajp-jphyslet_1982_43_17_625_0.pdf }}</ref><ref name="RammalToulouse1983">{{cite journal|last1=Rammal|first1=R.| last2=Toulouse|first2=G.|title=Random walks on fractal structures and percolation clusters|journal=Journal de Physique Lettres |volume=44|issue=1|year=1983|pages=13–22|doi=10.1051/jphyslet:0198300440101300|url=https://hal.archives-ouvertes.fr/jpa-00232136/document}}</ref> diffusion reactions processes<ref>{{cite journal|last=Smoluchowski|first=M.V.|journal=Z. Phys. Chem. | number=29| pages=129–168|year=1917|title=Versuch einer mathematischen Theorie der Koagulationskinetik kolloider Lösungen}},{{cite book|last=Rice|first=S.A.|title=Diffusion-Limited Reactions|url=https://books.google.com/books?id=sWiyspAjelsC&pg=PP2|access-date=13 August 2013|series=Comprehensive Chemical Kinetics|volume=25|date=1 March 1985|publisher=Elsevier | isbn=978-0-444-42354-2}}</ref>
and spread of populations in ecology.<ref name="Skellam1951">{{cite journal|last1=Skellam|first1=J. G.|title=Random Dispersal in Theoretical Populations|journal=Biometrika|volume=38|issue=1/2|year=1951|pages=196–218|doi=10.2307/2332328|jstor=2332328 | pmid=14848123}}</ref><ref>{{cite journal|last1=Skellam|first1=J. G.|title=Studies in Statistical Ecology: I. Spatial Pattern| journal=Biometrika|volume=39|issue=3/4|year=1952|pages=346–362|doi=10.2307/2334030|jstor=2334030}}</ref>