arXiv subjects

Hamzeh Alavirad

Publications and source records attributed to Hamzeh Alavirad.

7 recordsLinked to original sources

arXiv2026

Benchmarking Quantum Annealing for a Greenhouse-Inspired Control QUBO

We benchmark current annealing-based optimization workflows on a greenhouse-inspired quadratic unconstrained binary optimization problem for binary heater scheduling, where the horizon H denotes the number of hourly control decisions. For the main one-day instance (H=24), all solver outputs are decoded back into heater schedules and evaluated in the original greenhouse simulator using the same physical objective and feasibility criterion. Classical simulated annealing and path-integral simulated quantum annealing produce feasible near-optimal solutions in all repetitions, with best objectives close to the exact optimum. In contrast, the tested D-Wave Leap Hybrid BQM workflow is less reliable and does not outperform the classical baselines under 15--60~s requested time limits. Direct D-Wave QPU execution on reduced instances remains feasible in all runs and recovers the exact optimum for H=10 and H=12, but the exact-hit rate drops from 5/10 to 2/10 and then to 0/10 at H=14, with substantially higher variance than the classical baselines. The results do not indicate quantum advantage, but provide a reproducible, physically decoded benchmark that exposes the current strengths and limitations of classical, hybrid, and direct quantum annealing workflows on structured control QUBOs.

quant-ph↗

arXiv2026

Time-resolved digital quantum simulation of cosmological particle creation in a de Sitter-radiation transition

We present a time-resolved digital quantum simulation of cosmological particle creation in a de~Sitter--radiation FLRW transition. Instead of compiling only the final Bogoliubov transformation into a one-shot circuit, we discretize the conformal-time evolution and implement the dynamics as a Trotterized sequence of short-time circuit blocks. This formulation gives access not only to the late-time particle number, but also to the build-up of fixed-basis pair occupation during the non-adiabatic transition. Using a four-qubit single-excitation encoding for a momentum pair $(+\mathbf{k},-\mathbf{k})$, we compare matrix-Trotter evolution, noiseless statevector simulation, finite-shot Qiskit Aer simulation, and a shallow $N=1$ IBM hardware implementation. The simulator results are consistent with the analytic sudden-transition benchmark $n_k=1/[4(kη_e)^4]$ in the controlled single-excitation regime. The IBM experiment demonstrates execution of the shallow circuit block, but exhibits a residual hardware error of order $10^{-2}$, indicating that quantitative hardware reconstruction of the particle spectrum remains beyond current NISQ performance.

quant-ph↗

arXiv2014

Cosmological Constraints on Ghost Dark Energy in the Brans-Dicke Theory by Using MCMC Approach

By using a Markov Chain Monte Carlo simulation, we investigate cosmological constraints on the ghost dark energy (GDE) model in the framework of the Brans-Dicke (BD) theory. A combination of the latest observational data of the cosmic microwave background radiation data from seven-year WMAP, the baryon acoustic oscillation data form the SDSS, the supernovae type Ia data from the Union2 and the X-ray gas mass fraction data from the Chandra X-ray observations of the largest relaxed galaxy clusters are used to perform constraints on GDE in the BD cosmology. In this paper, we consider both flat and non-flat universes together with interaction between dark matter and dark energy. The main cosmological parameters are obtained as: $Ω_{\rm b}h^2= 0.0223^{+0.0016}_{-0.0013}$, $Ω_{\rm c}h^2=0.1149^{+0.0088}_{-0.0104}$ and $Ω_{\rm k}=0.0005^{+0.0025}_{-0.0073}$. In addition, the Brans-Dicke parameter $ω$ is estimated as $1/ω\simeq 0.002$.

astro-ph.CO↗

arXiv2014

Quintessence reconstruction of interacting HDE in a non-flat universe

In this paper we consider quintessence reconstruction of interacting holographic dark energy in a non-flat background. As system's IR cutoff we choose the radius of the event horizon measured on the sphere of the horizon, defined as $L=ar(t)$. To this end we construct a quintessence model by a real, single scalar field. Evolution of the potential, $V(ϕ)$, as well as the dynamics of the scalar field, $ϕ$, are obtained according to the respective holographic dark energy. The reconstructed potentials show a cosmological constant behavior for the present time. We constrain the model parameters in a flat universe by using the observational data, and applying the Monte Carlo Markov chain simulation. We obtain the best fit values of the holographic dark energy model and the interacting parameters as $c=1.0576^{+0.3010+0.3052}_{-0.6632-0.6632}$ and $ζ=0.2433^{+0.6373+0.6373}_{-0.2251-0.2251}$, respectively. From the data fitting results we also find that the model can cross the phantom line in the present universe where the best fit value of of the dark energy equation of state is $w_D=-1.2429$.

astro-ph.CO↗

arXiv2013

Observational constraints on G-corrected holographic dark energy using a Markov chain Monte Carlo method

We constrain holographic dark energy (HDE) with time varying gravitational coupling constant in the framework of the modified Friedmann equations using cosmological data from type Ia supernovae, baryon acoustic oscillations, cosmic microwave background radiation and X-ray gas mass fraction. Applying a Markov Chain Monte Carlo (MCMC) simulation, we obtain the best fit values of the model and cosmological parameters within $1σ$ confidence level (CL) in a flat universe as: $Ω_{\rm b}h^2=0.0222^{+0.0018}_{-0.0013}$, $Ω_{\rm c}h^2 =0.1121^{+0.0110}_{-0.0079}$, $α_{\rm G}\equiv \dot{G}/(HG) =0.1647^{+0.3547}_{-0.2971}$ and the HDE constant $c=0.9322^{+0.4569}_{-0.5447}$. Using the best fit values, the equation of state of the dark component at the present time $w_{\rm d0}$ at $1σ$ CL can cross the phantom boundary $w=-1$.

astro-ph.CO↗

arXiv2013

Modified gravity with logarithmic curvature corrections and the structure of relativistic stars

We consider the effect of a logarithmic f(R) theory, motivated by the form of the one-loop effective action arising from gluons in curved spacetime, on the structure of relativistic stars. In addition to analysing the consistency constraints on the potential of the scalar degree of freedom, we discuss the possibility of observational features arising from a fifth force in the vicinity of the neutron star surface. We find that the model exhibits a chameleon effect that completely suppresses the effect of the modification on scales exceeding a few radii, but close to the surface of the neutron star, the deviation from General Relativity can significantly affect the surface redshift that determines the shift in absorption (or emission) lines. We also use the method of perturbative constraints to solve the modified Tolman-Oppenheimer-Volkov equations for normal and self-bound neutron stars (quark stars).

gr-qc↗

arXiv2013

Interacting generalized ghost dark energy in non-flat universe

We investigate the generalized Quantum Chromodynamics (QCD) ghost model of dark energy in the framework of Einstein gravity. First, we study the non-interacting generalized ghost dark energy in a flat Friedmann-Robertson-Walker (FRW) background. We obtain the equation of state parameter, $w_D=p/ρ$, the deceleration parameter, and the evolution equation of the generalized ghost dark energy. We find that, in this case, $w_D$ cannot cross the phantom line ($w_D>-1$) and eventually the universe approaches a de-Sitter phase of expansion $(w_D\rightarrow-1)$. Then, we extend the study to the interacting ghost dark energy in both a flat and non-flat FRW universe. We find that the equation of state parameter of the interacting generalized ghost dark energy can cross the phantom line ($w_D<-1$) provided the parameters of the model are chosen suitably. Finally, we constrain the model parameters by using the Markov Chain Monte Carlo (MCMC) method and a combined dataset of SNIa, CMB, BAO and X-ray gas mass fraction.

gr-qc↗