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Probing symmetry-driven DEA dynamics in ozone investigated by velocity slice imaging technique
(AIP Publishing LLC, 2026-10-01)
Varghese, Melvin
;
Dharun, J
;
Mason, Nigel J
;
Krishnakumar, E
;
Prabhudesai, Vaibhav S
We report the results of a comprehensive experimental investigation of dissociative electron attachment (DEA) to ozone using the velocity slice imaging technique. We reveal several channels that yield both O^− and O^−2 from negative-ion resonances formed by electron attachment. Our results demonstrate that DEA to ozone proceeds through competition between symmetric and asymmetric dissociation pathways. This is governed by excitation of symmetric, asymmetric, and bending vibrational modes and likely involves vibronic coupling between the symmetry of the negative ion resonance states. At 1.6 eV, symmetric dissociation results in vibrationally excited O2 and O^−2 with near-thermal kinetic energies. An additional asymmetric dissociation pathway driven by overlapping contributions from ^2A1 and ^2 B2 states producing rotationally excited O2 with enhanced translational energy is identified. DEA from the second resonance yields both O^− and O^−2 with considerable internal energies arising from a single anionic state (^2B2) proceeding via an asymmetric dissociation mechanism. In the 4.1 − 4.4 eV region, overlapping resonances with A1 and B2 symmetry lead to asymmetric dissociation, accompanied by a notable increase in internal excitations of the molecular moieties. This also provides experimental evidence for the previously proposed ^2A1 shape resonance at 4.2 eV. At higher energies around 6.9 eV, angular distribution analysis reveals a contribution from an additional ^2A1 state, in contrast to the theoretically predicted ^2B2 state. These findings establish a unified picture of competing symmetric and asymmetric dissociation mechanisms that produce highly internally excited and chemically reactive fragments.
System for Generating Random Numbers and Method Thereof
(Government of India, 2026-07-07)
Sinha, Urbasi
;
Sinha, Aninda
;
Nath, Pingal Pratyush
Bayesian inference of peculiar motions of low-redshift galaxies from Type Ia supernova observations
(Oxford University Press, 2026-09-17)
Upadhyay, Ujjwal
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Saini, Tarun Deep
;
Sethi, Shiv K
The peculiar motions of galaxies are powerful cosmological probes that trace the growth of structures and the distribution of matter in the universe, providing a means to investigate the nature of dark energy and test gravity on cosmological scales. However, their direct observation is extremely challenging, as it requires independent and precise distance measurements to galaxies. We present a Bayesian approach to estimate the radial component of peculiar velocities of galaxies hosting Type Ia supernovae (SNe Ia), relying solely on the background cosmological model and the precision of the SN Ia data. Unlike other peculiar velocity estimators based on Hubble residuals, our method does not assume local linearity of the magnitude–redshift relation or a fixed cosmology, reducing potential bias even for large peculiar velocities and self-consistently avoiding bias due to a wrong cosmology. We validate our method using simulated supernova data with the precision of current and upcoming surveys, and further compare it with the linearized estimator to test its efficacy. We show that our estimator has lower bias than the standard estimator and remains consistent even for peculiar velocities comparable to the Hubble flow. We also present a Bayesian derivation for the linearized estimator generalized to include the supernova magnitude covariance.
Implementing Bell causality in quantum sequential growth
(American Physical Society, 2026-10-07)
Srivastava, Ritesh
;
Surya, Sumati
We explore different implementations of the quantum Bell causality (QBC) condition in the quantum sequential growth (QSG) dynamics of causal set quantum gravity, for noncommuting transition operators. Assuming a nonsingular dynamics we show that for the two most natural choices of operator orderings for the QBC, the transition operator algebra 𝒜 reduces to a commutative one. As a third choice, we take the operator ordering to depend on the size of the precursor set. We find several new commutation relations which further constrain 𝒜 but do not imply commutativity. On the other hand, if any of the generators of the “antichain subalgebra” 𝒬 belongs to its center, then this implies commutativity of 𝒜. The complexity of the algebra prevents us from obtaining a general form for the transition operators, which hinders computability. In an attempt to construct the simplest nontrivial 𝑑 =2 representation of 𝒜, we find that a Pauli matrix representation of the generators of 𝒬 leads to inconsistencies. Our work can be viewed as a first step toward finding a noncommutative realization of QSG.
Measuring a Quantum Measure Exceeding Unity
(Verein zur Förderung des Open Access Publizierens in den Quantenwissenschaften, 2026-09-24)
Chakraborti, Sanchari
;
Sorkin, Rafael D
;
Sinha, Urbasi
The history based formalism known as Quantum Measure Theory (QMT) generalizes the concept of probability-measure so as to incorporate quantum interference. The resulting quantum measure μ is defined for arbitrary events (sets of histories), not just for observables at a fixed moment of time. Thanks to interference effects, μ can exceed unity, exhibiting its non-classical nature in a particularly striking manner. Here, in an optical experiment, we illustrate an ancilla based filtering scheme that gives operational meaning to the quantum measure. For a specific photonic event E, we report a measured value of μ(E)=1.172+0.013−0.019, which within errors agrees with the theoretical value of 5/4, while exceeding the maximum value permissible for a classical probability (namely 1) by 13.32 upper or 8.89 lower percentile widths. The directly observed quantity is an ordinary detector probability pD≤1 (or, with laser light, an equivalent power ratio); the value μ(E)>1 is inferred via the calibrated relation μ(E)=2pD for our filter. If an unconventional theoretical concept is to play a role in meeting the foundational challenges of quantum theory, it seems important to bring it into contact with experiment as much as possible. Our experiment does this for the quantum measure.

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