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DTSTAMP:20260905T204409Z
LAST-MODIFIED:20150312T135445Z
DTSTART:20150318T150000Z
DTEND:20150318T160000Z
UID:event1419@bu.edu
URL:http://physics.bu.edu/internal/events/show/1419
SUMMARY:Symmetry protection of critical phases and global anomaly in 1+1 di
	mensions
DESCRIPTION:Featuring Prof. Masaki Oshikawa\, University of Tokyo\nHosted b
	y: Claudio Chamon\n\nPart of the Condensed Matter Theory Seminar Series.\n\
	nAbstract:\nClassification of gapless quantum phases remains very much open
	.\nSymmetries are naturally expected to play an important role here\,\nas i
	n the case of gapped quantum phases.\nIn this talk\, we argue that there is
	 a protection of bulk gapless\ncritical phases by discrete symmetry.  This 
	symmetry protection is\nanalogous to that of the well-known (gapped) Symmet
	ry-Protected\nTopological (SPT) phases; here we show that the concept can b
	e\ngeneralized to bulk gapless critical phases.  We demonstrate this\nfor t
	he SU(2)-symmetric quantum antiferromagnetic chains and\ntheir effective fi
	eld theory\, SU(2) Wess-Zumino-Witten (WZW)\ntheory as an example.  The SU(
	2) WZW theory is characterized\nby a natural number k\, which is called lev
	el.\nIn the presence of the SU(2) and a certain discrete Z$_2$\nsymmetry of
	 the WZW theory\, which corresponds to the\ntranslation symmetry of the spi
	n chain\, we find that\na renormalization-group (RG) flow is possible betwe
	en SU(2)\nWZW theories only if the difference in the levels is even.\nThat 
	is\,  gapless critical phases in 1+1 dimension with the SU(2)\, the\nZ$_2$\
	, and the Lorentz symmetries are classified into the two\n"symmetry-protect
	ed'' categories: one corresponds to even levels and\nthe other to odd level
	s.\n\n(in collaboration with S. C. Furuya)
LOCATION:SCI 328\, 590 Commonwealth Avenue\, 02215
STATUS:CONFIRMED
CLASS:PUBLIC
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