Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Unimodular loop quantum gravity and the problems of time   We develop the quantization of unimodular gravity in the Plebanski and
Ashtekar formulations and show that the quantum effective action defined by a
formal path integral is unimodular. This means that the effective quantum
geometry does not couple to terms in the expectation value of the
energy-momentum tensor proportional to the metric tensor. The path integral
takes the same form as is used to define spin foam models, with the additional
constraint that the determinant of the four metric is constrained to be a
constant by a gauge fixing term. We also review the proposal of Unruh, Wald and
Sorkin- that the hamiltonian quantization yields quantum evolution in a
physical time variable equal to elapsed four volume-and discuss how this may be
carried out in loop quantum gravity. This then extends the results of
arXiv:0904.4841 to the context of loop quantum gravity.

16
The categories of this paper are: stat
1
The categories of this paper are: cs
36
The categories of this paper are: cmp-lg
22
The categories of this paper are: chao-dyn
24
The categories of this paper are: dg-ga
37
The categories of this paper are: supr-con
32
The categories of this paper are: atom-ph
17
The categories of this paper are: q-fin
29
The categories of this paper are: funct-an
30
The categories of this paper are: q-alg
15
The categories of this paper are: nucl-ex
35
The categories of this paper are: mtrl-th
10
The categories of this paper are: q-bio
18
The categories of this paper are: econ
9
The categories of this paper are: nlin
20
The categories of this paper are: acc-phys