arXiv subjects

Muhammad Ghulam Khuwajah Khan

Publications and source records attributed to Muhammad Ghulam Khuwajah Khan.

3 recordsLinked to original sources

arXiv2026

Topolons: Stable Particle-Like Remnants of Collapsed Vacuum Bubbles in a Three-Form Gauge Sector

We study a three-form gauge sector in four spacetime dimensions coupled to electrically charged spherical membranes with Dirac--Born--Infeld (DBI) worldvolume dynamics. The associated four-form field strength has no local propagating degrees of freedom and contributes a branch-dependent vacuum energy. Motivated by the Hartle--Hawking--Wu selection argument, we restrict to the semiclassically admissible flux window and endow the membrane with a worldvolume $U(1)$ gauge field carrying quantized monopole flux $n\in\mathbb{Z}$. Evaluating the full DBI energy, we find that the energetically preferred branch collapses toward a microscopic core rather than stabilizing at finite radius. For nonzero monopole flux, however, the energy remains finite in the collapsed limit, yielding a stable flux-supported particle-like remnant whose mass is set by the wall scale and conserved flux. We call these objects topolons. Within the admissible sector, the energy analysis separates stable collapsed remnants from runaway vacuum-decay configurations, identifying the sector relevant for cosmological relic formation. At macroscopic distances, topolons behave as heavy localized states and constitute a concrete dark-relic candidate. More broadly, the construction provides the nonperturbative remnant sector of an economical three-form framework in which homogeneous four-form flux may neutralize the dominant permanent vacuum-energy contribution, while a dynamical scalar supplies the temporary positive energy required for no-boundary inflation. The detailed cosmological abundance, residual late-time vacuum energy, and phenomenology are left for future work.

gr-qc↗

arXiv2026

The tension of space as dark energy: dynamics and phenomenology

We develop a phenomenological model in which the observed late-time dark-energy sector is interpreted as an effective residual tension of space. Motivated by recent observational hints that the dark-energy equation of state may exhibit mild low-redshift evolution, we begin with an intrinsic membrane description of spacetime and show that a uniform space tension contributes to the gravitational field equations with precisely the tensor structure of vacuum energy. We then consider a Dirac--Born--Infeld completion, which naturally introduces a hidden Abelian gauge sector. A late-time hidden transition, $U(1)_h \, \to \, \mathbb{Z}_n$, can reorganize hidden magnetic energy into a coarse-grained flux-tube reservoir. If this reservoir exchanges energy with the dynamical part of the space-tension sector, the effective dark-energy density becomes time dependent and acquires a nontrivial equation of state. At the background level, the model gives a simple proof-of-concept realization of running dark energy and admits a transient crossing of the phantom divide. A restricted numerical scan shows that the best representative solution corresponds to a string-like hidden flux reservoir, with an effective low-redshift evolution that projects approximately to $(w_0^{\rm mod},w_a^{\rm mod})\simeq(-0.915,-0.457)$ in the Chevallier--Polarski--Linder plane. This does not exactly reproduce the compressed observational benchmark, but it generates a phenomenologically relevant departure from $Λ$CDM and illustrates how a late hidden-sector defect population can induce mild running of the residual vacuum-like tension of space. The construction is therefore best viewed as a physically transparent proof of concept rather than a complete theory of dark energy.

gr-qc↗

arXiv2026

Spatial Phonons: A Phenomenological Viscous Dark Energy Model for DESI

We explore a phenomenological model of dark energy in which space is treated as an elastic brane with uniform tension $T_s$ and supports a longitudinal phonon sector described by three scalar fields $ϕ^I$. At the background level the construction reproduces a perfect fluid whose enthalpy and bulk modulus are controlled by two dimensionless parameters $\varepsilon$ and $κ$, which encode the elastic and viscous response and determine both the effective equation of state $w_{\rm eff}(z)$ and the physical sound speed thriugh $c_s^2 = κ/\varepsilon$. Motivated by the consistency requirements of a phonon effective description, we focus on the stable regime $0 < κ< \varepsilon < 1$, which prevents tachyonic behavior and is natural given that $\varepsilon$ and $κ$ are defined as fractional response coefficients. To connect the model predictions to current observational summaries, we map $w_{\rm eff}(z)$ onto the Chevallier--Polarski--Linder form $w(z) = w_0 + w_a z/(1+z)$ over the redshift range relevant to DESI. We then use the public DESI DR1 compressed Gaussian likelihood in $(w_0,w_a)$ for BAO combined with Pantheon+ Type I a supernovae and Planck 2018, and scan the model parameter space to identify viable regions. We find that the model can reproduce the DESI compressed constraints at the background level, with representative best match values $(w_0,w_a) \simeq (-0.83,-0.74)$ and therefore, a near luminal sound speed $c_s^2 \simeq 0.9618$ as an output of the fit rather than a built in restriction. The covariance weighted distance is found to satisfy $χ^2 \ll 1$ in the $(w_0,w_a)$ plane. The associated phonon mass scale $m_ϕ= H_\star/(2π)$ is ultralight, corresponding to a Compton wavelength of order the cosmological horizon, consistent with interpreting the relevant excitations as infrared collective modes of the brane.

astro-ph.CO↗