group cohomology, nonabelian group cohomology, Lie group cohomology
cohomology with constant coefficients / with a local system of coefficients
differential cohomology
In string theory/M-theory, the shifted C-field flux quantization condition is a charge quantization-condition on the supergravity C-field expected in M-theory.
For the magnetic $G_4$-flux, the shifted flux quantization says that the real cohomology class of the flux density (field strength) differential 4-form $G_4 \in \Omega^4(X)$ on spacetime $X$ becomes integral after shifted by one quarter of the first Pontryagin class, hence the condition that with the shifted 4-flux density defined as
(for $\nabla_{T X}$ any affine connection on spacetime, in particular the Levi-Civita connection) we have (using the de Rham theorem to translate from de Rham cohomology to real cohomology) that $\widetilde G_4$ represents an integral cohomology-class:
This condition was originally argued for in (Witten 96a, Witten 96b) as a sufficient condition for ensuring that the prequantum line bundle for the 7d Chern-Simons theory on an M5-brane worldvolume is divisible by 2.
Proposals for encoding this condition by a Wu class-shifted variant of stable ordinary differential cohomology were considered in Hopkins-Singer 02, Diaconescu-Freed-Moore 03, FSS 12.
It turns out that the shifted flux quantization condition on the C-field is naturally implied (FSS1 19b, Prop. 4.12) by the requirement that $G_4$ is the differential form datum underlying, via Sullivan's theorem, a cocycle in unstable J- twisted Cohomotopy in degree 4 (Hypothesis H).
In the presence of non-vanishing C-field flux $G_4$, the electric flux density of M2-branes is not $G_7 \coloneqq \star G_4$ alone, but receives corrections, first due to the quadratic C-field self-interaction in D=11 supergravity, but then also due to the shifted C-field flux quantization expected in M-theory:
The 11d supergravity literature states the corrected 7-flux to be the following combination, also known as the Page charge (due to Page 83 (8), Duff-Stelle 91 (43), reviewed e.g. in BLMP 13, p. 21):
where the second term subtracts the electric flux induced by the self-intersection of the field, and also ensures that the full expression is a closed differential form if the naive 11d supergravity equations of motion hold:
But in fact (2) does not quite make general sense, for two reasons:
In general $G_4 = 0$ is not an admissible condition and is not the actual vanshing of the C-field, due to the shifted C-field flux quantization.
Even if $G_4$ happens to be intregrally quantizaed (if $\tfrac{1}{4}p_1$ is integral) the appearance of a globally defined C-field potential $C_3$ in (2),means that the total flux actually does vanish after all.
Charge-quantized $\widetilde G_7$-flux with shifted C-field flux quantization (FSS 19b, Prop. 4.3, FSS 19c, Section 4)
Both of these issues are solved if the C-field is taken to be charge quantized in J-twisted Cohomotopy (Hypothesis H). This gives the corrected formula
where
the expression lives on the homotopy pullback of the Sp(2)-parametrized quaternionic Hopf fibration
to spacetime, along the twisted Cohomotopy-cocycle that represents the C-field under Hypothesis H;
$\widetilde G_4 \coloneqq h^\ast G_4 + \tfrac{1}{4}h^\ast p_1(\nabla)$ is the integral shifted C-field pulled back to that 3-spherical fibration over spacetime;
$d H_3 = h^\ast G_4 - \tfrac{1}{4}h^\ast p_1(\nabla)$ trivializes not the C-field itself, but its pullback, and not absolutely but relative to the background charge implied by shifted C-field flux quantization.
With the corrected 7-flux in twisted Cohomotopy it becomes true that
the integral of $G_7$ around the 7-sphere linking a black M2-brane is always integer (FSS 19c, Theorem 4.6);
this integer satisfies the C-field tadpole cancellation condition (FSS 19b, Section 4.6).
The suggestion originates in
Edward Witten, On Flux Quantization In M-Theory And The Effective Action, J. Geom. Phys. 22:1-13, 1997 (arXiv:hep-th/9609122)
Edward Witten, Five-Brane Effective Action In M-Theory, J. Geom. Phys. 22:103-133, 1997 (arXiv:hep-th/9610234)
Proposals to model the condition by a Wu class-shifted variant of ordinary differential cohomology include
Michael Hopkins, Isadore Singer, Quadratic Functions in Geometry, Topology,and M-Theory J. Differential Geom. Volume 70, Number 3 (2005), 329-452. (arXiv:math.AT/0211216, euclid:1143642908)
E. Diaconescu, Dan Freed, Greg Moore, The $M$-theory 3-form and $E_8$-gauge theory, chapter in Haynes Miller, Douglas Ravenel (eds.) Elliptic Cohomology Geometry, Applications, and Higher Chromatic Analogues, Cambridge University Press 2007 (arXiv:hep-th/0312069, doi:10.1017/CBO9780511721489)
Dan Freed, Greg Moore, Setting the quantum integrand of M-theory, Communications in Mathematical Physics, Volume 263, Number 1, 89-132, (arXiv:hep-th/0409135, doi:10.1007/s00220-005-1482-7)
Greg Moore, Anomalies, Gauss laws, and Page charges in M-theory, Comptes Rendus Physique 6 (2005) 251-259 (arXiv:hep-th/0409158)
Domenico Fiorenza, Hisham Sati, Urs Schreiber, The moduli 3-stack of the C-field, Communications in Mathematical Physics, Volume 333, Issue 1 (2015), Page 117-151 (arXiv:1202.2455, doi:10.1007/s00220-014-2228-1)
The observation that the condition is implied by C-field charge quantization in J-twisted Cohomotopy (Hypothesis H) is due to
Last revised on January 22, 2020 at 12:46:39. See the history of this page for a list of all contributions to it.