Xiao-Gang Wen Home Page

String-net condensation -- a unification of light and electrons Q: Where do light and fermions come from? A: Light and fermions come from the qubits that form the space. Q: Why do light and fermions exist? A: Light and fermions exist because the space-forming qubits form a string-net condensed state. Q: What are light and fermions? A: Light waves are collective motions of strings and fermions are ends of open strings in the string-net condensed state.

• For details, click a talk (pdf) and Theory of everything (for some universes)
• String-net unification on Big Bang Theory: Series 2 Episode 06 - The Cooper-Nowitzki Theorem (transcripts) (video)

Articles and lecture notes

Talks

Recent Publications

• Symmetry protected topological orders and the group cohomology of their symmetry group (pdf)
  Xie Chen, Zheng-Cheng Gu, Zheng-Xin Liu, and Xiao-Gang Wen
  arXiv:1106.4772
  Introduced group cohomology theory into condensed matter physics to describe short-range entangled phases with symmetry for interacting bosons.
 
• Emergence of helicity +/- 2 modes (gravitons) from qubit models (pdf)
  Zheng-Cheng Gu and Xiao-Gang Wen
  arXiv:0907.1203, Nuclear Physics B online
  .
  • Constructed two quantum spin models on a lattice which gives rise to emergent gravitons (one with ω = k and the other with ω = k^3 dispersion).
  • After 6 years, many journals (Science, PRL, PRB, NJP, JHEP, NPB), and about 30 exchanges, one of our linear quantum gravity papers finally get published in Nucl. Phys. B. Next problem: how non-linear quantum gravity can emerge from some lattice models.
  • The referee reports and our replies represent detailed discussions between parties who have different points of view on quantum gravity: emergence point of view vs geometry/gauge point of view. The exchange of opinions is important and helpful for the development of the difficult field of quantum gravity. So, I would like to share those exchanges with the researchers in the field.
    • Submit the short paper to PRL:
      2006/5/25 Report from PRL, 2006/6/8 Reply to PRL, 2006/7/28 Report from PRL, 2006/11/7 Reply to PRL, 2007/1/3 Report from PRL, 2012/5/18 A late reply to PRL.
    • Resubmit the short paper to PRL and submit the long paper to PRB:
      2009/9/22 Report from PRL, 2009/9/25 Reply to PRL, 2009/9/25 Report from PRB, 2009/9/30 Reply to PRB, 2009/10/19 Report from PRB, 2009/10/25 Reply to PRB, 2009/10/30 Report from PRL, 2009/10/31 Reply to PRL.
    • Tried to appeal the rejection decision from PRB and PRL:
      2009/11/4 Reply to PRB, 2009/11/5 Reply to PRL, 2009/12/10 Appeal report from PRB/PRL, 2010/2/8 Appeal reply to PRB/PRL.
    • Submit the long paper to NPB (and get rejected again):
      2010/3/5 Report from NPB, 2010/3/6 Reply to NPB, 2010/3/8 Report from NPB, 2010/3/10 Report from NPB, 2010/3/15 Reply to NPB, 2010/4/16 Report from NPB, 2010/4/20 Reply to NPB.
    • 2012/5: Following Hong Liu's suggestion, we moved the long introduction of the long paper to appendix and resubmited the long paper to NPB. This time, it was accepted [:-)
 
• Photons and electrons as emergent phenomena (pdf)
  Michael A. Levin and Xiao-Gang Wen
  Rev. Mod. Phys. 77, 871-879 (2005), cond-mat/0407140
  String-net condensation provides a way to unify light and electrons.
 
• String-net condensation: A physical mechanism for topological phases (pdf)
  Michael Levin and Xiao-Gang Wen
  Phys. Rev. B71, 045110 (2005). cond-mat/0404617
  Introduced tensor category theory into condensed matter physics to describe long-range entangled phases (ie topologically ordered phases) for interacting bosons.

Publications

• Theory of quantum order and string-net condensation
• Theory of everything (for some universes)
• Theory of topological order
• Topological order and quantum computation
• Gauge theory of high Tc superconductors
• Theory of fractional quantum Hall edge state
• Superfluidity/superconductivity in double-layer quantum Hall systems
• Topological superfluids

Java Simulations

Current and previous students/postdocs