1,086 research outputs found
On the relation between boundary proposals and hidden symmetries of the extended pre-big bang quantum cosmology
A framework associating quantum cosmological boundary conditions to
minisuperspace hidden symmetries has been introduced in \cite{7}. The scope of
the application was, notwithstanding the novelty, restrictive because it lacked
a discussion involving realistic matter fields. Therefore, in the herein
letter, we extend the framework scope to encompass elements from a
scalar-tensor theory in the presence of a cosmological constant. More
precisely, it is shown that hidden minisuperspace symmetries present in a
pre-big bang model suggest a process from which boundary conditions can be
selected.Comment: 15 pages, no figures, to appear in European Physical Journal
Evaluation of the growth potential of Paulownia furtunei in Guilan Province
Paulownia furtunei is a fast-growing tree which under optimal conditions can produce useful timber in five to six years. The wood of this species has properties suited for a variety of applications. This species is highly adaptable with regard to planting site, and is widely distributed. Its natural distribution ranges from tropical through to temperate climates. P. furtunei is cultivated in many locations including in the Golestan Province of Northern Iran. To evaluate diameter and height growth potential of P. furtunei in Guilan in order to use this species in forest farming or cultivated forests with the purpose of rapid exploitation of timber in Guilan Province, an area of about 3000 m2 was selected in Shanderman Nursery and was planted at a 4 m by 4 m spacing. The diameter at breast height (dbh) and total height were measured after planting and again in the second and third year to estimate diameter and height growth potential and some important characteristics were analyzed. Growth measurements will be continued for at least five or six years. The dbh and height annual increment of P. fortunei were 3.24 cm and 1.88 m in the second year and 4.87 cm and 3.23 m in the third year, respectively. The mean dbh and annual height increment were 4.12 cm and 2.61 m up to the third year. A parabloid relationship between height and dbh was estimated. If the current growth rate continues, it seems that growth of P. fortunei in Guilan Province is suitable and comparable to its natural distribution areas
EFT Compatible PBHs: Effective Spawning of the Seeds for Primordial Black Holes during Inflation
Most of the inflationary scenarios that try to explain the origin of
Primordial Black Holes (PBHs) from the enhancements of the power spectrum to
values of order one, at the relevant scales, run into clashes with the
Effective Field Theory (EFT) criteria or fail to enhance the power spectrum to
such large amplitudes. In this paper, we unravel a mechanism for enhancing the
power spectrum during inflation that does not use the flattening of the
potential or reduction of the sound speed of scalar perturbations. The
mechanism is based on this observation in the formalism of Extended EFT of
inflation (EEFToI) with the sixth order polynomial dispersion relation for
scalar perturbations that if the quartic coefficient in the dispersion relation
is negative and smaller than a certain threshold, the amplitude of the power
spectrum is enhanced substantially. The instability mechanism must arrange to
kick in at the scales of interest related to the mass of the PBHs one would
like to produce, which can be ten(s) of solar mass PBHs, suitable for LIGO
events, or solar mass PBHs, which can comprise the whole
dark matter energy density. We argue that the strong coupling is avoided for
the range of parameters that the mechanisms enhance the power spectrum to the
required amount.Comment: v1:1+18 pages, 5 figures; v2: 1+21 pages, 5 figures, matched the JHEP
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