The field equations of TGD defining the space-time surfaces have interpretation as conservation laws for isometry charges and therefore have a hydrodynamics character. The hydrodynamic character is actually characterized in quite concrete ways (see this, this, and this).
Also nuclear and hadron physics suggest applications for Quantum Hydrodynamics (QHD). The basic vision about what happens in high energy nuclear and hadron collisions is that two BSFRs take place. The first BSFR creates the intermediate state with heff>h: the entire system formed by colliding systems need not be in this state. In nuclear physics this state corresponds to a dark nucleus which decays in the next BSFR to ordinary nuclei.
The basic notions are the notion of dark matter at MB and ZEO, in particular the change of the arrow of time in BSFR.
1. Cold fusion, nuclear tunnelling, ℏeff, and BSFRs
This model allows us to understand "cold fusion" in an elegant manner (see this, this, and this). The dark protons at flux tubes associated with water and created by the Pollack effect have much smaller nuclear binding energy than ordinary nucleons. This energy is compensated to a high degree by the positive Coulomb binding energy which corresponds roughly to distance given by electron Compton length.
Dark nuclear reactions between these kinds of objects do not require large collision energy to increase the value of heff and can take place at room temperature. After the reaction the dark nuclei can transform to ordinary nuclei and liberate the ordinary nuclear binding energy. One can say that in ordinary nuclear reactions one must get to the top of the energy hill and in "cold fusion" one already is at the top of the hill.
Quite generally, the mechanism creating intermediate dark regions in the system of colliding nuclei in BSFR, would be the TGD counterpart of quantum tunnelling in the description of nuclear reactions based on Schrödinger equation. This mechanism could be involved with all tunnelling phenomena.
2. QHD and hadron physics
Hadron physics suggests applications of QHD.
2.1 Quark gluon plasma and QHD
In hadron physics quark gluon plasma (see this) has turned out to be what it was thought to be originally. Instead of being like a gas of quarks and gluons with a relatively large dissipation, it has turned out to behave like almost perfect fluid. This means that the ratio η/s of viscosity and entropy is near to its minimal value proposed by string model based arguments to be η/s=ℏ/m.
To be a fluid means that the system has long range correlations whereas in gas the particles move randomly and one cannot assign to the system any velocity field or more general currents. In the TGD framework, the existence of a velocity field means at the level of the space-time geometry generalized Beltrami flow allowing to define a global coordinate varying along the flow lines (see this and this). This would be a geometric property of space-time surfaces and the finite size of the space-time surface would serve as a limitation.
In the TGD framework the replacement ℏ→ ℏeff requires that s increases in the same proportion. If the fluid flow is realized in terms of vortices controlled by pairs of monopole flux tubes defining their cores and Lagrangian flux tubes with gradient flow defining the exteriors of the cores, this situation is achieved.
In this picture entropy could but need not be associated with the monopole flux tubes with non-Beltrami flow and with non-vanishing entropy since the number of the geometric degrees of freedom is infinite which implies limiting temperature known has Hagedorn temperature TH which is about 175 MeV for hadrons, and slightly higher than pion mass. In fact, the Beltrami property holds for the flux tubes with 2-D CP2 projection, which is a complex manifold for monopole flux tubes. The fluid flow associated with (controlled by) the monopole flux tubes would have non-vanishing vorticity for monopole fluxes and could dissipate.
The monopole flux tube at the core of the vortex could therefore serve as the source of entropy. One expects that η/s as minimal value is not affected by h→ heff. One expects that s → (ℏeff/ℏ)s= ns since the dimension of the extension of rationals multiplies the Galois degrees of freedom by n.
Almost perfect fluids are known to allow almost non-interacting vortices. For a perfect fluid, the creation of vortices is impossible due to the absence of friction at the walls. This suggests that the ordinary viscosity is not the reason for the creation of vortices, and in the TGD picture the situation is indeed this. The striking prediction is that the masses of Sun and Earth appear as basic parameters in the gravitational Compton lengths Λgr determining νgr= Λgrc.
2.2 The phase transition creating quark gluon plasma
The phase transition creating what has been called quark gluon plasma is now what it was expected to be. That the outcome behaves like almost perfect fluid was the first example. TGD leads however to a proposal that since quantum criticality is involved, phases with ℏeff>h must be present.
p-Adic length scale hypothesis led to the proposal (see this and this) that this transition could allow production of so called M89 hadrons characterized by Mersenne prime M89=289-1 whereas ordinary hadrons would correspond to M107. The mass scale of M89 hadrons would be by a factor 512 higher than that of ordinary hadrons and there are indications for the existence of scaled versions of mesons.
How M89 hadrons could be created. The temperature TH= 175 MeV is by a factor 1/512 lower than the mass scale of M89 pion. Somehow the colliding nuclei or hadrons must provide the needed energy from their kinetic energy. What certainly happens is that this energy is materialized in the ordinary nuclear reaction to ordinary pions and other mesons. The mesons should correspond to closed flux tubes assignable to circular vortices of the highly turbulent hydrodynamics flow created in the collision.
Could roughly 512 mesonic flux tubes reconnect to circular but flattened long flux tubes having length of M89 meson, which is 512 times that of ordinary pions? I have proposed this kind of process, analogous to BEC, to be fundamental in both biology (see this, this, and this) and also to explain the strange findings of Eric Reiter challenging some basic assumptions of nuclear physics if taken at face value (see this).
The process generating an analog of BEC would create in the first BSFR M89 mesons having ℏeff/ℏ=512. In the second BSFR the transition ℏeff→ ℏ would take place and yield M89 mesons. It would seem that part of the matter of the composite system ends up to n M89 hadronic phase with 512 times higher TH. In the number theoretic picture, these BEC like states would be Galois confined states (see this and this).
2.3 Can the size of a quark be larger than the size of a hadron?
The Compton wavelength Λc= ℏ/m is inversely proportional to mass. This implies that the Compton length of the quark as part of the hadron is longer than the Compton length of the hadron. If one assigns to Compton length a geometric interpretation as one does in M8-H duality mapping mass shell to CD with radius given by Compton length, this sounds paradoxical. How can a part be larger than the whole? One can think of many approaches to what might look like a paradox.
One could of course argue that being a part in the sense of tensor product has nothing to with being a part in geometric sense. However, if one requires quantum classical correspondence (QCC), one could argue that a hadron is a small region to which much larger quark 3-surfaces are attached.
One could also say that Compton length characterizes the size of the MB assignable to a particle which itself has size of order CP2 length scale. In this case the strange looking situation would appear only at the level of MBs and the magnetic bodies could have sizes which increase when the particle mass decreases.
What if one takes QCC completely seriously? One can look at the situation in ZEO.