Can dark energy be expressed as a power series of the Hubble parameter?

Rezaei, Mehdi; Malekjani, M.; Peracaula, Joan Solà

doi:10.1103/physrevd.100.023539

Cited by 75 publications

(164 citation statements)

References 128 publications

(245 reference statements)

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“…Depending on whether one considers an interaction of the dynamical DE with matter or assumes self-conservation of the DE, one can favor the lower value of H 0 measured by the Planck Collaboration [1] or push this value higher. This feature has been demonstrated recently in [31], where it is shown that, upon the assumptions that the DE adopts the RVM form, and does not interact with matter, it is possible to simultaneously decrease the value of σ 8 and increase the prediction on H 0 , such that the fitted value of H 0 definitely becomes much closer to the local value determined by Riess et al [30].…”

mentioning

confidence: 56%

“…Such a form of DE leads to an overall improvement of the fit of the cosmological observations as compared to the case of a rigid Λ-term [14][15][16][17]. In addition, that dynamical component of the DE can help alleviate some of the tensions presently existing in the ΛCDM concerning σ 8 [15] and H 0 [31].…”

Section: Discussionmentioning

confidence: 99%

“…For a homogeneous and isotropic FLRW space-time, and axion field b(t), for which only the temporal derivative is non zero, we obtain from (36) We next proceed to discuss the equation of state of the KR fluid. From (31), and taking into account the generic relation for the stress-energy tensor for an observer moving with a four-velocity u µ with respect to an inertial frame…”

Section: A the Primordial Effective Action With (Gravitational) Anommentioning

confidence: 99%

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Gravitational and chiral anomalies in the running vacuum universe and matter-antimatter asymmetry

2020

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We present a model for the Universe in which quantum anomalies are argued to play an important dual rôle: they are responsible for generating matter-antimatter asymmetry in the Cosmos, but also provide time-dependent contributions to the vacuum energy density of "running-vacuum" type, which drive the Universe evolution. According to this scenario, during the inflationary phase of a string-inspired Universe, and its subsequent exit, the existence of primordial gravitational waves induce gravitational anomalies, which couple to the (Kalb-Ramond (KR)) axion field emerging from the antisymmetric tensor field of the massless gravitational multiplet of the string. Such anomalous CP violating interactions have two important effects: first, they lead to contributions to the vacuum energy density of the form appearing in the "running vacuum model" (RVM) framework, which are proportional to both, the square and the fourth power of the effective Hubble parameter, H 2 and H 4 respectively. The H 4 terms may lead to inflation, in a dynamical scenario whereby the rôle of the inflaton is played by the effective scalar-field ("vacuumon") representation of the RVM. Second, there is an undiluted KR axion at the end of inflation, which plays an important rôle in generating matter-antimatter asymmetry in the Cosmos, through baryogenesis via leptogenesis in models involving heavy right handed neutrinos. As the Universe exits inflation and enters a radiation dominated era, the generation of chiral fermionic matter is responsible for the cancellation of gravitational anomalies, thus restoring diffeomorphism invariance for the matter/radiation (quantum) theory, as required for consistency. Chiral U(1) anomalies may remain uncompensated, though, during matter/radiation dominance, providing RVM-like H 2 and H 4 contributions to the Universe energy density. Finally, in the current era, when the Universe enters a de Sitter phase again, and matter is no longer dominant, gravitational anomalies resurface, leading to RVM-like H 2 contributions to the vacuum energy density, which are however much more suppressed, as compared to their counterparts during inflation, due to the smallness of the present era's Hubble parameter H 0 . In turn, this feature endows the observed dark energy with a dynamical character that follows the RVM pattern, a fact which has been shown to improve the global fits to the current cosmological observations as compared to the concordance ΛCDM with its rigid cosmological constant , Λ > 0. Our model favours axionic Dark Matter, the source of which can be the KR axion. The uncompensated chiral anomalies in late epochs of the Universe are argued to play an important rôle in this, in the context of cosmological models characterised by the presence of large-scale cosmic magnetic fields at late eras.

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confidence: 56%

Section: Discussionmentioning

confidence: 99%

Section: A the Primordial Effective Action With (Gravitational) Anommentioning

confidence: 99%

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Gravitational and chiral anomalies in the running vacuum universe and matter-antimatter asymmetry

2020

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“…On the other hand, despite the fact that the ΛCDM model is found to be in a very good agreement with the majority of cosmological data [7], nonetheless the model seems to be currently in tension with some recent measurements [32][33][34][35], related with the Hubble constant H 0 and the present value of the mass variance at 8h −1 Mpc, namely σ 8 . Moreover, Lusso et al [1] using a combined Hubble diagram of SNIa, Quasars, and gamma-ray bursts (GRBs) found a ∼ 4σ tension between the best fit cosmographic parameters with respect to those of ΛCDM (see also [2,36]).…”

Section: Introductionmentioning

confidence: 82%

Does $$\varLambda $$CDM really be in tension with the Hubble diagram data?

Mehrabi

Basilakos

2020

Eur. Phys. J. C

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In this article, we elaborate further on the $$\varLambda $$ Λ CDM “tension”, suggested recently by the authors Lusso et al. (Astron Astrophys 628:L4, 2019) and Risaliti and Lusso (Nat Astron 3(3):272, 2019). We combine Supernovae type Ia (SNIa) with quasars (QSO) and Gamma Ray Bursts (GRB) data in order to reconstruct in a model independent way the Hubble relation to as high redshifts as possible. Specifically, in the case of either SNIa or SNIa/QSO data we find that the current values of the cosmokinetic parameters extracted from the Gaussian process are consistent with those of $$\varLambda $$ Λ CDM. Including GRBs in the analysis we find a tension, which lies between $$2\sigma $$ 2 σ and $$3\sigma $$ 3 σ levels respectively. Finally, we find that at high redshifts ($$z>1$$ z > 1 ) the corresponding cosmokinetic parameters significantly deviate from those of $$\varLambda $$ Λ CDM, hence the possibility of new Physics is not precluded by the present analysis.

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“…As it has been shown in the literature, models mimicking a time-evolving (and hence a dynamical vacuum energy density ρ ) could help in alleviating these problems, see e.g. [16][17][18][19][20][21][22][23][24][25][26][27] and [28][29][30][31][32][33][34][35][36][37][38][39][40].…”

Section: Introductionmentioning

confidence: 99%

Running vacuum in quantum field theory in curved spacetime: renormalizing $$\rho _{vac}$$ without $$\sim m^4$$ terms

2020

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The $$\Lambda $$Λ-term in Einstein’s equations is a fundamental building block of the ‘concordance’ $$\Lambda $$ΛCDM model of cosmology. Even though the model is not free of fundamental problems, they have not been circumvented by any alternative dark energy proposal either. Here we stick to the $$\Lambda $$Λ-term, but we contend that it can be a ‘running quantity’ in quantum field theory (QFT) in curved space time. A plethora of phenomenological works have shown that this option can be highly competitive with the $$\Lambda $$ΛCDM with a rigid cosmological term. The, so-called, ‘running vacuum models’ (RVM’s) are characterized by the vacuum energy density, $$\rho _{vac}$$ρvac, being a series of (even) powers of the Hubble parameter and its time derivatives. Such theoretical form has been motivated by general renormalization group arguments, which look plausible. Here we dwell further upon the origin of the RVM structure within QFT in FLRW spacetime. We compute the renormalized energy-momentum tensor with the help of the adiabatic regularization procedure and find that it leads essentially to the RVM form. This means that $$\rho _{vac}(H)$$ρvac(H) evolves as a constant term plus dynamical components $${{\mathcal {O}}}(H^2)$$O(H2) and $$\mathcal{O}(H^4)$$O(H4), the latter being relevant for the early universe only. However, the renormalized $$\rho _{vac}(H)$$ρvac(H) does not carry dangerous terms proportional to the quartic power of the masses ($$\sim m^4$$∼m4) of the fields, these terms being a well-known source of exceedingly large contributions. At present, $$\rho _{vac}(H)$$ρvac(H) is dominated by the additive constant term accompanied by a mild dynamical component $$\sim \nu H^2$$∼νH2 ($$|\nu |\ll 1$$|ν|≪1), which mimics quintessence.

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Can dark energy be expressed as a power series of the Hubble parameter?

Cited by 75 publications

References 128 publications

Gravitational and chiral anomalies in the running vacuum universe and matter-antimatter asymmetry

Gravitational and chiral anomalies in the running vacuum universe and matter-antimatter asymmetry

Does $$\varLambda $$CDM really be in tension with the Hubble diagram data?

Running vacuum in quantum field theory in curved spacetime: renormalizing $$\rho _{vac}$$ without $$\sim m^4$$ terms

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