Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Primordial scalar power spectrum from the hybrid approach in loop
  cosmologies   We compare the primordial scalar power spectra in the loop cosmological
models using the effective dynamics of the hybrid approach to cosmological
perturbations in which the background is loop quantized but the perturbations
are Fock quantized. The three loop cosmological models under consideration are
the standard LQC, the modified LQC-I (mLQC-I) and the modified LQC-II (mLQC-II)
in the spatially flat Friedmann-Lema\^itre-Robertson-Walker (FLRW) universe
with a Starobinsky potential. These models arise from different regularizations
of the classical Hamiltonian constraint in the symmetry reduced spacetimes and
aim to capture certain features of quantization in loop quantum gravity. When
applying the techniques in the hybrid approach to mLQC-I/II, we find the
effective Mukhanov-Sasaki equations take the same form as in LQC. The
difference among the three models is encoded in the unique expressions of the
effective masses in each model. We find that the relative difference in the
amplitude of power spectrum between LQC and mLQC-II is approximately $50\%$ in
the infrared and the oscillatory regimes, whereas this difference can be as
large as $100\%$ between mLQC-I and LQC/mLQC-II. Interestingly, in the infrared
and the oscillatory regimes of mLQC-I, we obtain a suppressed power spectrum
from the hybrid approach which is far below the Planck scale. This result is in
a striking contrast to the one obtained from dressed metric approach to
perturbations where the corresponding amplitude in this regime is extremely
large. Our analysis shows that while the phenomenological predictions are in
agreement between two approaches for LQC and mLQC-II, for mLQC-I the
differences between dressed and hybrid approaches can be quite significant. Our
result provides the first robust evidence of difference in predictions between
dressed and hybrid approaches due to respective underlying constructions.

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The categories of this paper are: bayes-an
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The categories of this paper are: dg-ga
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The categories of this paper are: q-bio
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The categories of this paper are: cs
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The categories of this paper are: hep-lat
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The categories of this paper are: nucl-th
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The categories of this paper are: comp-gas
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The categories of this paper are: mtrl-th
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The categories of this paper are: atom-ph
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The categories of this paper are: ao-sci
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The categories of this paper are: physics
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The categories of this paper are: math
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The categories of this paper are: alg-geom
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The categories of this paper are: solv-int
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The categories of this paper are: nucl-ex
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The categories of this paper are: cmp-lg