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Quintessential Implications of the presence of AdS in the Dark Energy sector

Purba Mukherjee, Dharmendra Kumar, Anjan A Sen

Abstract

We explore the implications for an Anti-de Sitter (AdS) vacuum, equivalently a negative cosmological constant (nCC), in the dark energy (DE) sector using current cosmological observations. Our joint analysis uses DESI BAO, DESY5 supernovae, and P-ACT CMB (ACT-DR6 + Planck) measurements. We also use the KiDS weak-lensing measurement to cross-check consistency with the inferred value of $S_{8}$. Within the Chevallier--Polarski--Linder parametrization for the evolving component of the DE, the inclusion of an AdS term provides a theoretically motivated mechanism that opens up a finite non-phantom region in the CPL parameter space while remaining compatible with current observations. A negative cosmological constant also implies a finite cosmic lifetime, thereby linking observational DE phenomenology to broader questions in quantum gravity and string theory.

Quintessential Implications of the presence of AdS in the Dark Energy sector

Abstract

We explore the implications for an Anti-de Sitter (AdS) vacuum, equivalently a negative cosmological constant (nCC), in the dark energy (DE) sector using current cosmological observations. Our joint analysis uses DESI BAO, DESY5 supernovae, and P-ACT CMB (ACT-DR6 + Planck) measurements. We also use the KiDS weak-lensing measurement to cross-check consistency with the inferred value of . Within the Chevallier--Polarski--Linder parametrization for the evolving component of the DE, the inclusion of an AdS term provides a theoretically motivated mechanism that opens up a finite non-phantom region in the CPL parameter space while remaining compatible with current observations. A negative cosmological constant also implies a finite cosmic lifetime, thereby linking observational DE phenomenology to broader questions in quantum gravity and string theory.

Paper Structure

This paper contains 5 sections, 6 equations, 5 figures, 2 tables.

Table of Contents

  1. Introduction
  2. Theoretical Framework
  3. Data and Methodology
  4. Results and Discussions
  5. Concluding Remarks

Figures (5)

  • Figure 1: Evolution of $E(z)/E^{\Lambda \rm CDM}(z)$ showing a comparison between CPLCCCDM vs CPLCDM at $1\sigma-2\sigma$ CL with P-ACT+DESI+DESY5 data.
  • Figure 2: 2D confidence contours at 68% and 95% CL for $w_0$ and $w_a$, to compare between CPLCDM and CPLCCCDM with: (a) P-ACT+DESI, (b) P-ACT+DESI+DESY5 data. (c) Plot for $w_0 + w_a$ vs. $\Omega_\Lambda$ for CPLCCDM. $\Omega_\Lambda=0$ denotes CPLCDM.
  • Figure 3: Evolution of the (a) total DE EoS $w_{\rm DE}(z)$, along with (b) the fluid's EoS, $w_\phi(z)$ for the CPLCCCDM model, derived from the P-ACT+DESI+DESY5 chains which satisfy the non-phantom behaviour at 2$\sigma$ CL.
  • Figure 4: 2D confidence contours at 68% and 95% CL for $H_0$ and $S_8$, comparing $w$CDM and $w$CCCDM models, obtained using KiDS, and P-ACT+DESI data.
  • Figure 7: Posterior distribution of the total lifespan of the universe $\boldsymbol{T}$ (in Gyrs), assuming (a) $w$CCCDM and (b) CPLCCCDM using P-ACT+DESI+DESY5 chains. (c) Reconstruction of $V(\phi)$ vs $\phi$ for CPLCC vs CPL.