Editing Metric signature (section)

==Signature change==
If a metric is regular everywhere then the signature of the metric is constant. However if one allows for metrics that are degenerate or discontinuous on some hypersurfaces, then signature of the metric may change at these surfaces.<ref>{{cite journal
|last1=Dray    |first1=Tevian
|last2=Ellis   |first2=George
|last3=Hellaby |first3=Charles
|last4=Manogue |first4=Corinne A.
|title          =Gravity and signature change
|journal        =General Relativity and Gravitation
|volume         =29
|pages          =591–597
|doi            =10.1023/A:1018895302693
|year           =1997
|issue=5
|arxiv          =gr-qc/9610063
|bibcode = 1997GReGr..29..591D |s2cid=7617543
}}</ref> Such signature changing metrics may possibly have applications in [[physical cosmology|cosmology]] and [[quantum gravity]].