infrared limit
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2021 ◽  
Vol 81 (10) ◽  
Author(s):  
Milad Solbi ◽  
Kayoomars Karami

AbstractWithin the framework of inflationary model with field-dependent kinetic term for quartic and natural potentials, we investigate generation of the primordial black holes (PBHs) and induced gravitational waves (GWs). In this setup, we consider a kinetic function as $$G(\phi )=g_I(\phi )\big (1+g_{II}(\phi )\big )$$ G ( ϕ ) = g I ( ϕ ) ( 1 + g II ( ϕ ) ) and show that in the presence of first term $$g_I(\phi )$$ g I ( ϕ ) both quartic and natural potentials, in contrast to the standard model of inflation, can be consistent, with the 68% CL of Planck observations. Besides, the second term $$g_{II}(\phi )$$ g II ( ϕ ) can cause a significant enhancement in the primordial curvature perturbations at the small scales which results the PBHs formation. For the both potentials, we obtain an enhancement in the scalar power spectrum at the scales $$k\sim 10^{12}~{\mathrm{Mpc}}^{-1}$$ k ∼ 10 12 Mpc - 1 , $$10^{8}~{\mathrm{Mpc}}^{-1}$$ 10 8 Mpc - 1 , and $$10^{5}~{\mathrm{Mpc}}^{-1}$$ 10 5 Mpc - 1 , which causes PBHs production in mass scales around $$10^{-13}M_{\odot }$$ 10 - 13 M ⊙ , $$10^{-5}M_{\odot }$$ 10 - 5 M ⊙ , and $$10 M_{\odot }$$ 10 M ⊙ , respectively. Observational constraints confirm that PBHs with a mass scale of $$10^{-13}M_{\odot }$$ 10 - 13 M ⊙ can constitute the total of dark matter in the universe. Furthermore, we estimate the energy density parameter of induced GWs which can be examined by the observation. Also we conclude that it can be parametrized as a power-law function $$\Omega _{\mathrm{GW}}\sim (f/f_c)^n$$ Ω GW ∼ ( f / f c ) n , where the power index equals $$n=3-2/\ln (f_c/f)$$ n = 3 - 2 / ln ( f c / f ) in the infrared limit $$f\ll f_{c}$$ f ≪ f c .


Author(s):  
Ikfal Hanafi ◽  
Thamrin Thamrin
Keyword(s):  

Tujuan penelitian yaitu merancang hardware dan software alat perekat kantong kertas, mengkoordinir kerja alat menggunakan motor DC, mengatur gerak motor servo, mengatur sistem utama dan mengendalikan hardware melalui Arduino Mega, merancang dan membangun perangkat lunak. Rancang bangun alat perekat kantong kertas berbasis miktrokontroler ATMEGA2560 menggunakan sensor infrared, limit switch, motor servo, driver motor, motor DC, LCD 16x2, keypad dan Arduino Mega. Arduino Mega pada alat ini berfungsi sebagai pusat kendali program. Keypad adalah tombol pemilih menu proses landscape dan protrait yang ditampilkan pada LCD. Motor servo berfungsi untuk menggerakan kuas lem. Hasil penelitian ini yaitu diperoleh sebuah alat yang dapat digunakan untuk merekatkan kantong kertas pembungkus fried chicken dengan sistem terkontrol menggunakan Mikrokontroler ATMEGA2560.


2021 ◽  
Vol 36 (13) ◽  
pp. 2150074
Author(s):  
J. Gamboa ◽  
J. López-Sarrión

Spontaneous symmetry breaking is studied in the ultralocal limit of a scalar quantum field theory, that is when [Formula: see text] (or infrared limit). In this infrared approximation the theory [Formula: see text] is formally two-dimensional and its Euclidean solutions are instantons. For BPST-like solutions with [Formula: see text], the map between [Formula: see text] in two dimensions and self-dual Yang–Mills theory is carefully discussed.


2021 ◽  
Vol 81 (5) ◽  
Author(s):  
Nicolò Burzillà ◽  
Breno L. Giacchini ◽  
Tibério de Paula Netto ◽  
Leonardo Modesto

AbstractIn the present work we investigate the Newtonian limit of higher-derivative gravity theories with more than four derivatives in the action, including the non-analytic logarithmic terms resulting from one-loop quantum corrections. The first part of the paper deals with the occurrence of curvature singularities of the metric in the classical models. It is shown that in the case of local theories, even though the curvature scalars of the metric are regular, invariants involving derivatives of curvatures can still diverge. Indeed, we prove that if the action contains $$2n+6$$ 2 n + 6 derivatives of the metric in both the scalar and the spin-2 sectors, then all the curvature-derivative invariants with at most 2n covariant derivatives of the curvatures are regular, while there exist scalars with $$2n+2$$ 2 n + 2 derivatives that are singular. The regularity of all these invariants can be achieved in some classes of nonlocal gravity theories. In the second part of the paper, we show that the leading logarithmic quantum corrections do not change the regularity of the Newtonian limit. Finally, we also consider the infrared limit of these solutions and verify the universality of the leading quantum correction to the potential in all the theories investigated in the paper.


Author(s):  
Alessandro Giuliani ◽  
Vieri Mastropietro ◽  
Marcello Porta

AbstractWeyl semimetals are 3D condensed matter systems characterized by a degenerate Fermi surface, consisting of a pair of ‘Weyl nodes’. Correspondingly, in the infrared limit, these systems behave effectively as Weyl fermions in $$3+1$$ 3 + 1 dimensions. We consider a class of interacting 3D lattice models for Weyl semimetals and prove that the quadratic response of the quasi-particle flow between the Weyl nodes is universal, that is, independent of the interaction strength and form. Universality is the counterpart of the Adler–Bardeen non-renormalization property of the chiral anomaly for the infrared emergent description, which is proved here in the presence of a lattice and at a non-perturbative level. Our proof relies on constructive bounds for the Euclidean ground state correlations combined with lattice Ward Identities, and it is valid arbitrarily close to the critical point where the Weyl points merge and the relativistic description breaks down.


Author(s):  
Iosif L. Buchbinder ◽  
Ilya L. Shapiro

This chapter is devoted to the direct explicit calculations of non-local form factors in two-point functions in real scalar field theory. Two simple examples in flat spacetime demonstrate the relationship between logarithmic ultraviolet (UV) divergences in the cut-off and dimensional regularizations, which is used for deriving the form factors. The chapter then shows how one can establish the direct relation between logarithmic UV divergences and the logarithmic behavior of the momentum-dependent non-local form factors in the UV. In the low-energy (infrared) limit, it is possible to observe quadratic decoupling with respect to the mass of the quantum field. In curved space, analogous results are reproduced using the generally covariant heat-kernel solution. Calculations are given in full details.


2016 ◽  
Vol 2016 (11) ◽  
Author(s):  
Joshua Eby ◽  
Peter Suranyi ◽  
Cenalo Vaz ◽  
L. C. R. Wijewardhana
Keyword(s):  

2015 ◽  
Vol 2015 (3) ◽  
Author(s):  
Joshua Eby ◽  
Peter Suranyi ◽  
Cenalo Vaz ◽  
L. C. R. Wijewardhana
Keyword(s):  

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