2014/10/31 by Xiao-Gang Wen · 5 citations
Mathematics · Physics and Astronomy · #Black Holes and Theoretical Physics #Boundary (topology) #Cohomology #Combinatorics #Computer science #Group (periodic table) #Group cohomology #Mathematical analysis #Mathematics #Noncommutative and Quantum Gravity Theories #Physics #Pure mathematics #Quantum mechanics #Space (punctuation) #Topological Materials and Phenomena #Topology (electrical circuits) #cond-mat.str-el #hep-th
paper · pdf · doi:10.1103/physrevb.91.205101
published as Phys. Rev. B 91, 205101 (2015) · 39 pages, 10 figure. PRB version
arxiv created 2015/03/23 · openalex publication_date 2015/05/04 · arxiv updated 2015/05/13 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
It has been shown that the bosonic symmetry-protected-trivial (SPT) phases with pure gauge anomalous boundary can all be realized via nonlinear \ensuremathσ models (NL\ensuremathσMs) of the symmetry group G with various topological terms. Those SPT phases (called the pure SPT phases) can be classified by group cohomology Hd(G,ℝ/ℤ). But there are also SPT phases with mixed gauge-gravity anomalous boundary (which will be called the mixed SPT phases). Some of the mixed SPT states were also referred as the beyond-group-cohomology SPT states. In this paper, we show that those beyond-group-cohomology SPT states are actually within another type of group cohomology classification. More precisely, we show that both the pure and the mixed SPT phases can be realized by G\ifmmode×\else\texttimes\fiSO(\ensuremath∞) NL\ensuremathσMs with various topological terms. Through the group cohomology Hd[G\ifmmode×\else\texttimes\fiSO(\ensuremath∞),ℝ/ℤ], we find that the set of our constructed SPT phases in d-dimensional space-time are described by Ed(G)\ensuremath\rtimes\ensuremath\bigoplusk=1^d\ensuremath-1Hk(G,iTOL^d\ensuremath-k)\ensuremath\bigoplusHd(G,ℝ/ℤ) where G may contain time reversal. Here iTOLd is the set of the topologically ordered phases in d-dimensional space-time that have no topological excitations, and one has iTOL1=iTOL2=iTOL4=iTOL6=0,\phantom\rule0.16em0exiTOL3=ℤ,\phantom\rule0.16em0exiTOL5=ℤ2,\phantom\rule0.16em0exiTOL7=2ℤ. For G=U(1)\ensuremath\rtimesZ2T (charge conservation and time-reversal symmetry), we find that the mixed SPT phases beyond Hd[U(1)\ensuremath\rtimesZ2T,ℝ/ℤ] are described by ℤ2 in 3 + 1D, ℤ in 4 + 1D, 3ℤ2 in 5 + 1D, and 4ℤ2 in 6 + 1D. Our construction also gives us the topological invariants that fully characterize the corresponding SPT and iTO phases. Through several examples, we show how the universal physical properties of SPT phases can be obtained from those topological invariants.