Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Fluid phonons, protoinflationary dynamics and large-scale gravitational
  fluctuations   We explore what can be said on the effective temperature and sound speed of a
statistical ensemble of fluid phonons present at the onset of a conventional
inflationary phase. The phonons are the actual normal modes of the gravitating
and irrotational fluid that dominates the protoinflationary dynamics. The
bounds on the tensor to scalar ratio result in a class of novel constraints
involving the slow roll parameter, the sound speed of the phonons and the
temperature of the plasma prior to the onset of inflation. If the current size
of the Hubble radius coincides with the inflationary event horizon redshifted
down to the present epoch, the sound speed of the phonons can be assessed from
independent measurements of the tensor to scalar ratio and of the tensor
spectral index.

36
The categories of this paper are: cmp-lg
3
The categories of this paper are: physics
31
The categories of this paper are: ao-sci
33
The categories of this paper are: plasm-ph
22
The categories of this paper are: chao-dyn
34
The categories of this paper are: chem-ph
35
The categories of this paper are: mtrl-th
20
The categories of this paper are: acc-phys
4
The categories of this paper are: cond-mat
17
The categories of this paper are: q-fin
10
The categories of this paper are: q-bio
14
The categories of this paper are: math-ph
25
The categories of this paper are: patt-sol
15
The categories of this paper are: nucl-ex
26
The categories of this paper are: bayes-an
37
The categories of this paper are: supr-con