Adelic physics corresponds to a hierarchy of extensions of rationals inducing extensions of padic number fields and the proposal is that ramified primes of extension correspond to preferred padic primes.
 Adelic physics suggests that prime p and quite generally, all preferred padic primes, could correspond to ramified primes for the extension of rationals defining the adele. Ramified prime divides discriminant D(P) of the irreducible polynomial P (monic polynomial with rational coefficients) defining the extension (see this).
Discriminant D(P) of polynomial whose, roots give rise to extension of rationals, is essentially the resultant Res(P,P') for P and its derivative P' defined as the determinant of so called Sylvester polynomial (see this). D(P) is proportional to the product of differences r_{i}r_{j}, i≠ j the roots of p and vanishes if there are two identical roots.
Remark: For second order polynomials P(x)=x^{2}+bx+c one has D= b^{2}4c.
 Ramified primes divide D. Since the matrix defining Res(P,P') is a polynomial of coefficients of p of order 2n1, the size of ramified primes is bounded and their number is finite. The larger coefficients P(x) has, the larger the value of ramified prime can be. Small discriminant means small ramified primes so that polynomials having nearly degenerate roots have also small ramifying primes. Galois ramification is of special interest: for them all primes of extension in the decomposition of p appear as same power. For instance, the polynomial P(x)=x^{2}+p has discriminant D=4p so that primes 2 and p are ramified primes.
 What does ramification mean algebraically? The ring O(K)/(p) of integers of the extension K modulo p=π_{i}^{ei} can be written as product ∏_{i} O/π_{i}^{ei} (see this). If p is ramified, one has e_{i}>1 for at least one i. Therefore there is at least one nilpotent element in O(K)/(p).
Could one interpret nilpotency quantum physically?
 For Galois extensions one has e_{i}=e>1 for ramified primes. e divides the dimension of extension. For the quadratic extensions ramified primes have e=2. Quadratic extensions are fundamental extensions  kind of conserved genes , whose further extensions give rise to physically relevant extensions.
On the other hand, fermionic oscillator operators and Grassmann number used to describe fermions "classically" are nilpotent. Could they correspond to nilpotent elements of order e_{i}=e=2 in O(K)/(p)? Fermions are building bricks of all elementary particles in TGD. Could this number theoretic analogy for the fermionic statistics have a deeper meaning?
 What about ramified primes with e_{i}=e>2? Could they correspond to parastatistics (see this) or braid statistics (see this)?
Both parabosonic and parafermionic fields of order n have the representation Ψ=∑_{i=1}^{n} Ψ_{i}. For parafermion field one has {Ψ_{i}(x),Ψ_{i}(y)}=0
and [Ψ_{i}(x),Ψ_{j}(y)]=0, i≠ j, when x and y have spacelike separation.
For parabosons the roles of commutator and anticommutator are changed.
The states containing N identical parafermions are described by a representation of symmetric group S_{N} with N rows with at most e columns (antisymmetrization). For states containing N identical parabosons one has N columns and at most e rows. For parafermions the wave function is symmetric in horizontal direction but the modes are different so that BoseEinstein condensation is not possible.
For parafermion of order n operator ∑_{i=1}^{n} Ψ_{i} one has (∑_{i=1}^{n} Ψ_{i})^{n}= ∏ Ψ_{1} Ψ_{2}...Ψ_{n} and higher powers vanish so that one would have enilpotency. Therefore the interpretation for the nilpotent elements of order e in O(K)/(p)$ in terms of parafermion of order n=e1 might make sense.
It seems impossible to build a nilpotent operator from parabosonic field Ψ= ∑_{i}Ψ_{i}: the reason is that the powers Ψ_{i}^{n} are nonvanishing for arbitrarily high values of n.
 Braid statistics differs from parastatistics and is assigned with quantum groups. It would naturally correspond to quantum phase exp(iπ/p) assignable to the exchange of particles by braid operation regarded as a homotopy permuting braid strands. Could ramified prime p would correspond to braid statistics and the index e_{i}=e characterizing it to parastatistics of order e1? This possibility cannot be excluded since this exotic physics would be associated in TGD framework to dark matter assigned to algebraic extensions of rationals whose dimension n equals to h_{eff}/h_{0}.
Why the primes, which do not split maximally in given extension  the ramified ones  would be physically special?
 Do ramified primes possess exceptional evolutionary fitness and are ramified primes present for lowerdimensional extensions present also for higherdimensional extensions? If higher extensions are formed as extensions of already existing extensions, this is the case. Hierarchy of polynomials of polynomials would to this kind of hierarchy with ramified primes of starting point polynomials analogous to conserved genes.
 Quadratic extensions are the simplest ones and could serve as starting point extensions. Polynomials of form x^{2}c are the simplest among them. Discriminant is now D= 4c.
 Why c= M_{n}=2^{n}1 allowing p=2 and Mersenne prime p=M_{n} as ramified primes would be favored? Extension of rationals defined by x=2^{n} is nontrivial for odd n and is equivalent with extension containing 2^{1/2}. c=M_{n}=2^{n}1 as a small deformation of c=2^{n} gives an extension having both 2 as M_{n} as ramified primes.
For c=M_{n} the number of ramified primes is smallest possible and equal to 2: why minimal number of ramified primes would give rise to a fittest extension? Why smallest number of fermionic padic mass scales assignable to the ramified primes would be the fittest option?
The padic length scale corresponding ro M_{n} would be maximal and mass scale minimal. Could one think that other quadratic extension are unstable against transforming to Mersenne extensions with smallest padic mass scale?
See the chapter Quantum Arithmetics and the Relationship between Real and pAdic Physics.
