arXiv subjects

Petar Suman

Publications and source records attributed to Petar Suman.

3 recordsLinked to original sources

arXiv2026

Primordial non-Gaussianity constraints on dissipative inflation

Dissipative effects appear in many early-Universe scenarios, yet their universal observational signatures and systematic confrontation with data remain largely unexplored. We employ the Open Effective Field Theory of Inflation (Open EFToI) to consistently incorporate dissipative and stochastic effects while preserving scale invariance. Dissipation enhances specific interaction channels of the Goldstone mode, generating distinctive primordial non-Gaussian signatures, beyond those generically produced by standard EFToI. In the weak-dissipation regime, this includes folded bispectrum shapes observationally more favoured than both the equilateral and orthogonal templates. Using the Modal bispectrum pipeline with the Planck CMB data, we obtain the likelihood and derive the first model-independent bounds on early-Universe dissipation. We find a marginalised upper bound on the dissipation scale $γ\leq 384\,H$ and a lower bound on the sound speed $c_s \geq 0.38$ at $95\%$ confidence level. The maximum likelihood for best-fit models reveals a degeneracy between $γ$ and $c_s$. These results open a model-independent window for probing departures from minimal inflation and discriminating between early-Universe scenarios with stochastic noise and dissipative effects.

astro-ph.CO↗

arXiv2025

Searching for Cosmological Collider in the Planck CMB Data II: collider templates and Modal analysis

Signatures of massive particles during inflation are highly informative targets for cosmological experiments. With recent progress on both theoretical and observational frontiers, we have reached the point where these novel signals of primordial non-Gaussianities (PNG) can be systematically tested with increasingly precise data. In this paper, we present the results of improved CMB data analysis for cosmological collider signals using Planck CMB data. To set the stage, we first construct a set of simplified but characteristic collider templates which are accurate over a broad range of particle masses, spins and sound speeds. In order to break degeneracies with single-field PNG, we propose an orthogonalization scheme such that the collider templates are uncorrelated with the highly constrained equilateral and orthogonal shapes. On this basis, we deploy the Modal bispectrum estimator for the Planck analysis and perform a systematic scan of parameters to search for the most significant collider signal. The maximum signal-to-noise ratio is found to be $2.35σ$ for massive spin-0 exchange after taking into account the look-elsewhere effect. In addition, we cross-validate the Modal analysis with the CMB-BEST pipeline, which demonstrates the consistency of results across the benchmark examples of collider templates. Given the low signal-to-noise ratio regime we find at the current stage of PNG observations, we believe the orthogonalization procedure provides an optimized strategy for future tests of the cosmological collider with the ability to rule out single field inflation.

astro-ph.CO↗

arXiv2025

How Significant are Cosmological Collider Signals in the Planck Data?

The search for primordial non-Gaussianities (PNG) is theoretically well motivated but remains observationally challenging. Tight constraints with low significance for the standard non-Gaussian shapes suggest that detection may lie beyond the reach of near-future experiments. However, tests of PNG are highly template-dependent. From a theory perspective, a whole new family of bispectrum shapes arise in the cosmological collider program, with distinct signatures of heavy particles during inflation. In this work, we provide a class of simplified collider templates for these particles that encompasses a broader range of masses, sound speeds, and interactions. We propose that, given the current state of observations, the most effective strategy to search for PNG signals is through orthogonalizing the collider templates, such that they are uncorrelated with the tightly constrained single field predictions. Using the Modal pipeline and Planck CMB data, we perform a systematic parameter scan of the collider templates with the most significant result reaching $2.4σ$ for spin-0, after taking into account the look-elsewhere effect; indicative results for spin-1 and spin-2 peak near 2$σ$. These results indicate that, with refined collider templates and improved data analysis strategies, there are credible prospects with forthcoming observations to detect PNG and also rule out single field inflation.

astro-ph.CO↗