The writing of an article about possible condensed matter applications of TGD led to a considerable progress in TGD itself and in the following I shall briefly summarize also this progress.
It is perhaps good to explain what TGD is not and what it is or hoped to be.
 "Geometro" refers to the idea about the geometrization of physics. The geometrization program of Einstein is extended to gauge fields allowing realization in terms of the geometry of surfaces so that Einsteinian spacetime as abstract Riemann geometry is replaced with submanifold geometry. The basic motivation is the loss of classical conservation laws in General Relativity Theory (GRT). Also the interpretation as a generalization of string models by replacing string with 3D surface is natural.
Standard model symmetries uniquely fix the choice of 8D space in which spacetime surfaces live to H=M^{4}× CP_{2}. Also the notion of twistor is geometrized in terms of surface geometry and the existence of twistor lift fixes the choice of H completely so that TGD is unique. The geometrization applies even to the quantum theory itself and the space of spacetime surfaces  "world of classical worlds" (WCW)  becomes the basic object endowed with Kähler geometry. General Coordinate Invariance (GCI) for spacetime surfaces has dramatic implications. Given 3surface fixes the spacetime surface almost completely as analog of Bohr orbit (preferred extremal).This implies holography and leads to zero energy ontology (ZEO) in which quantum states are superpositions of spacetime surfaces.
 Consider next the attribute "Topological". In condensed matter physical topological physics has become a standard topic. Typically one has fields having values in compact spaces, which are topologically nontrivial. In the TGD framework spacetime topology itself is nontrivial as also the topology of H=M^{4}× CP_{2}.
The spacetime as 4surface X^{4} ⊂ H has a nontrivial topology in all scales and this together with the notion of manysheeted spacetime brings in something completely new. Topologically trivial Einsteinian spacetime emerges only at the QFT limit in which all information about topology is lost.
Practically any GCI action has the same universal basic extremals: CP_{2} type extremals serving basic building bricks of elementary particles, cosmic strings and their thickenings to flux tubes defining a fractal hierarchy of structure extending from CP_{2} scale to cosmic scales, and massless extremals (MEs) define spacetime correletes for massless particles. World as a set or particles is replaced with a network having particles as nodes and flux tubes as bonds between them serving as correlates of quantum entanglement.
"Topological" could refer also to padic number fields obeying padic local topology differing radically from the real topology.
 Adelic physics fusing real and various padic physics are part of the number theoretic vision, which provides a kind of dual description for the description based on spacetime geometry and the geometry of "world of classical" orders. Adelic physics predicts two fractal length scale hierarchies: padic length scale hierarchy and the hierarchy of dark length scales labelled by h_{eff}=nh_{0}, where n is the dimension of extension of rational. The interpretation of the latter hierarchy is as phases of ordinary matter behaving like dark matter. Quantum coherence is possible in all scales.
The concrete realization of the number theoretic vision is based on M^{8}H duality. The physics in the complexification of M^{8} is algebraic  field equations as partial differential equations are replaced with algebraic equations associating to a polynomial with rational coefficients a X^{4} mapped to H by M^{8}H duality. The dark matter hierarchy corresponds to a hierarchy of algebraic extensions of rationals inducing that for adeles and has interpretation as an evolutionary hierarchy.
M^{8}H duality provides two complementary visions about physics, and can be seen as a generalization of the qp duality of wave mechanics, which fails to generalize to quantum field theories (QFTs).
 In Zero energy ontology (ZEO), the superpositions of spacetime surfaces inside causal diamond (CD) having their ends at the opposite lightlike boundaries of CD, define quantum states. CDs form a scale hierarchy.
Quantum jumps occur between these and the basic problem of standard quantum measurement theory disappears. Ordinary state function reductions (SFRs) correspond to "big" SFRs (BSFRs) in which the arrow of time changes. This has profound thermodynamic implications and the question about the scale in which the transition from classical to quantum takes place becomes obsolete. BSFRs can occur in all scales but from the point of view of an observer with an opposite arrow of time they look like smooth time evolutions.
In "small" SFRs (SSFRs) as counterparts of "weak measurements" the arrow of time does not change and the passive boundary of CD and states at it remain unchanged (Zeno effect).
The writing of the article summarizing TGD and its possible condensed matter applications led to considerable progress in several aspects of TGD and also forced to challenge some aspects of the earlier picture.
 The mutual entanglement of fermions (bosons) as elementary particles is always maximal so that only fermionic and bosonic degrees can entangle in QFTs. The replacement of pointlike particles with 3surfaces forces us to reconsider the notion of identical particles from the category theoretical point of view. The number theoretic definition of particle identity seems to be the most natural and implies that the new degrees of freedom make possible geometric entanglement.
Also the notion particle generalizes: also manyparticle states can be regarded as particles with the constraint that the operators creating and annihilating them satisfy commutation/anticommutation relations. This leads to a close analogy with the notion of infinite prime.
 The understanding of the details of the M^{8}H duality forces us to modify the earlier view. The notion of causal diamond (CD) central to zero energy ontology (ZEO) emerges as a prediction at the level of H. The preimage of CD at the level of M^{8} is a region bounded by two mass shells rather than CD. M^{8}H duality maps the points of cognitive representations as momenta of quarks with fixed mass in M^{8} to either boundary of CD in H.
 Galois confinement at the level of M^{8} is understood at the level of momentum space and is found to be necessary. Galois confinement implies that quark momenta in suitable units are algebraic integers but integers for Galois singlet just as in ordinary quantization for a particle in a box replaced by CD. Galois confinement could provide a universal mechanism for the formation of all bound states.
 There is considerable progress in the understanding of the quantum measurement theory based on ZEO. From the point of view of cognition BSFRs would be like heureka moments and the sequence of SSFRs would correspond to an analysis having as a correlate the decay of 3surface to smaller 3surfaces.
The improved vision allows us to develop the TGD interpretation for various condensed matter notions.
 TGD is analogous to hydrodynamics in the sense that field equations at the level of H reduce to conservation laws for isometry charges. The preferred extremal property meaning that spacetime surfaces are simultaneous extremals of volume action and Kähler action allows interpretation in terms of induced gauge fields. The generalized Beltrami property implies the existence of an integrable flow serving as a correlate for quantum coherence. Conserved Beltrami flows currents correspond to gradient flows. At the QFT limit this simplicity would be lost.
 The fields H, M, B and D, P, E needed in the applications of Maxwell's theory could emerge at the fundamental level in the TGD framework and reflect the deviation between Maxwellian and the TGD based view about gauge fields due to CP_{2} topology.
 The understanding of macroscopic quantum phases improves. The role of the magnetic body carrying dark matter is central. The understanding of the role of WCW degrees of freedom improves considerably in the case of BoseEinstein condensates of bosonic particles such as polaritons. M^{8} picture allows us to understand the notion of skyrmion. The formation of Cooper pairs and analogous states with higher energy would correspond to a formation of Galois singlets liberating energy used to increase h_{eff}. What is new is that energy feed makes possible supraphases and their analogs above the critical temperature.
 Fermi surface emerges as a fundamental notion at the level of M^{8} but has a counterpart also at the level of H. Galois groups would be crucial for understanding braids, anyons and fractional Quantum Hall effect. Spacetime surface could be seen as a curved quasicrystal associated with the lattice of M^{8} defined by algebraic integers in an extension of rationals. Also the TGD analogs of condensed matter Majorana fermions emerge.
See the chapter The recent view about TGD and applications to condensed matter or the article with the same title.
