#### Pregled bibliografske jedinice broj: 214501

## Effective equation of state for dark energy: mimicking quintessence and phantom energy through a variable Lambda

Effective equation of state for dark energy: mimicking quintessence and phantom energy through a variable Lambda

*// Physics letters. B,*

**624**(2005), 147-157 (međunarodna recenzija, članak, znanstveni)

**Naslov**

Effective equation of state for dark energy: mimicking quintessence and phantom energy through a variable Lambda

(Effective equation of state for dark energy: Mimicking quintessence and phantom energy through a variable Lambda)

**Autori**

Sola, J ; Štefančić, Hrvoje

**Izvornik**

Physics letters. B (0370-2693) **624**
(2005);
147-157

**Vrsta, podvrsta i kategorija rada**

Radovi u časopisima, članak, znanstveni

**Ključne riječi**

Dark energy; quintessence; cosmological constant

**Sažetak**

While there is mounting evidence in all fronts of experimental cosmology for a non-vanishing dark energy component in the Universe, we are still far away from understanding its ultimate nature. A fundamental cosmological constant, Lambda, is the most natural candidate, but many dynamical mechanisms to generate an effective Lambda have been devised which postulate the existence of a peculiar scalar field (so-called quintessence, and generalizations thereof). These models are essentially ad hoc, but they lead to the attractive possibility of a time-evolving dark energy with a non-trivial equation of state (EOS). Most, if not all, future experimental studies on precision cosmology (e.g. the SNAP and PLANCK projects) address very carefully the determination of an EOS parametrized ``a la quintessence''. Here we show that by fitting cosmological data to an EOS of that kind can also be interpreted as a hint of a fundamental, but time-evolving, cosmological term: Lambda=Lambda(t). We exemplify this possibility by studying the effective EOS associated to a renormalization group (RG) model for Lambda. We find that the effective EOS can correspond to both normal quintessence and phantom dark energy, depending on the value of a single parameter of the RG model. We conclude that behind a non-trivial EOS of a purported quintessence or phantom scalar field there can actually be a running cosmological term of a fundamental quantum field theory.

**Izvorni jezik**

Engleski

**Znanstvena područja**

Fizika

**POVEZANOST RADA**

**Projekt / tema**

0098002

**Ustanove**

Institut "Ruđer Bošković", Zagreb

**Autor s matičnim brojem:**

Hrvoje Štefančić, (235826)

#### Časopis indeksira:

- Current Contents Connect (CCC)
- Web of Science Core Collection (WoSCC)
- Science Citation Index Expanded (SCI-EXP)
- SCI-EXP, SSCI i/ili A&HCI
- Scopus