Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Imprints of Relic Gravitational Waves in Cosmic Microwave Background
  Radiation   A strong variable gravitational field of the very early Universe inevitably
generates relic gravitational waves by amplifying their zero-point quantum
oscillations. We begin our discussion by contrasting the concepts of relic
gravitational waves and inflationary `tensor modes'. We explain and summarize
the properties of relic gravitational waves that are needed to derive their
effects on CMB temperature and polarization anisotropies. The radiation field
is characterized by four invariants I, V, E, B. We reduce the radiative
transfer equations to a single integral equation of Voltairre type and solve it
analytically and numerically. We formulate the correlation functions
C^{XX'}_{\ell} for X, X'= T, E, B and derive their amplitudes, shapes and
oscillatory features. Although all of our main conclusions are supported by
exact numerical calculations, we obtain them, in effect, analytically by
developing and using accurate approximations. We show that the TE correlation
at lower \ell's must be negative (i.e. an anticorrelation), if it is caused by
gravitational waves, and positive if it is caused by density perturbations.
This difference in TE correlation may be a signature more valuable
observationally than the lack or presence of the BB correlation, since the TE
signal is about 100 times stronger than the expected BB signal. We discuss the
detection by WMAP of the TE anticorrelation at \ell \approx 30 and show that
such an anticorrelation is possible only in the presence of a significant
amount of relic gravitational waves (within the framework of all other common
assumptions). We propose models containing considerable amounts of relic
gravitational waves that are consistent with the measured TT, TE and EE
correlations.

15
The categories of this paper are: nucl-ex
4
The categories of this paper are: cond-mat
21
The categories of this paper are: adap-org
34
The categories of this paper are: chem-ph
31
The categories of this paper are: ao-sci
12
The categories of this paper are: nucl-th
11
The categories of this paper are: hep-lat
25
The categories of this paper are: patt-sol
27
The categories of this paper are: comp-gas
16
The categories of this paper are: stat
33
The categories of this paper are: plasm-ph
18
The categories of this paper are: econ
17
The categories of this paper are: q-fin
22
The categories of this paper are: chao-dyn
14
The categories of this paper are: math-ph
37
The categories of this paper are: supr-con