Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Initial Condition Problem is Intractable in Cosmology   Determining the initial state of the universe is a challenging problem in
quantum cosmology and we argue that the issue is intractable if the basic
postulates of quantum mechanics are not modified in a nontrivial way. Namely a
"standard" quantum theory of gravity is expected to resolve the big-bang
singularity either by yielding a regular past eternal evolution or by a smooth
finite beginning; in both cases the initial state can in principle be totally
arbitrary. We illustrate this point in a minisuperspace, gauge fixed,
deparametrized toy model where there is a smooth beginning of the universe
provided by the matter Hamiltonian degenerating to the zero operator. This
arbitrariness is the source of several debates in the literature, especially in
relation to inflation, which can only be solved by a new paradigm involving
initial conditions that necessarily alters the usual quantum mechanical
treatment, but we argue that this is highly improbable.

6
The categories of this paper are: astro-ph
33
The categories of this paper are: plasm-ph
23
The categories of this paper are: solv-int
16
The categories of this paper are: stat
30
The categories of this paper are: q-alg
11
The categories of this paper are: hep-lat
9
The categories of this paper are: nlin
37
The categories of this paper are: supr-con
26
The categories of this paper are: bayes-an
29
The categories of this paper are: funct-an
10
The categories of this paper are: q-bio
19
The categories of this paper are: eess
24
The categories of this paper are: dg-ga
4
The categories of this paper are: cond-mat
15
The categories of this paper are: nucl-ex
17
The categories of this paper are: q-fin