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Orbital degrees of freedom play an essential role in metals, semiconductors, and strongly confined electronic systems. Experiments with ultracold atoms have used highly anisotropic confinement to explore low-dimensional physics, but they typically eliminate orbital degrees of freedom by preparing atoms in the motional ground states of the strongly confined directions. Here, we prepare multiband systems of spin-polarized fermionic potassium (K40) in the quasi-one-dimensional (q1D) regime and quantify the strength of atom-atom correlations using radio-frequency spectroscopy. The activation of orbital degrees of freedom leads to a new phenomenon: a low-energy scattering channel that has even particle-exchange parity along the q1D axis, as if the underlying interactions weres-wave. This emergent exchange symmetry is enabled by orbital singlet wave functions in the strongly confined directions, which also confer high-momentum components to low-energy q1D collisions. We measure both the q1D odd-wave and even-wave “contact” parameters for the first time and compare them to theoretical predictions of one-dimensional many-body models. The strength and spatial symmetry of interactions are tuned by ap-wave Feshbach resonance and by transverse confinement strength. Near resonance, the even-wave contact approaches its theoretical unitary value, whereas the maximum observed odd-wave contact remains several orders of magnitude below its unitary limit. Low-energy scattering channels of multi-orbital systems, such as those found here, may provide new routes for the exploration of universal many-body phenomena.

Understanding the dynamics of short-range correlations is a central challenge in strongly interacting Fermi gases. In ultracold gases, these correlations are quantified by the contact parameter, yet measurements to date have been limited to equilibrium systems or relatively slow, global dynamics. Here, we introduce a rapid spectroscopic technique based on projection of the interacting state onto an alternate scattering channel with a low-lying dimer state. We demonstrate contact measurements on the microsecond timescale -- faster than the inverse Fermi energy. Using \\(^40\\)K near a broad \\(s\\)-wave Feshbach resonance, we show that the strength of the dimer-projection feature scales proportionally with the contact parameter extracted from the high-frequency tail of radio-frequency spectroscopy, in agreement with coupled-channels calculations. Analysis of the spectra further reveals that the dimer feature provides the dominant contribution to the clock shift of the unitary Fermi gas, allowing the first experimental bound on this quantity. The observed deviations from universal predictions highlight the importance of multichannel effects. Our results open new avenues for studying contact correlators, hydrodynamic attractors, and quantum critical behavior.

Orbital degrees of freedom play an essential role in metals, semiconductors, and strongly confined electronic systems. Experiments with ultracold atoms have used highly anisotropic confinement to explore low-dimensional physics, but typically eliminate orbital degrees of freedom by preparing motional ground states in strongly confined directions. Here we prepare multi-band systems of spin-polarized fermionic potassium (\\(^40\\)K) in the quasi-one-dimensional (q1D) regime and quantify the strength of atom-atom correlations using radio-frequency spectroscopy. The activation of orbital degrees of freedom leads to a new phenomenon: a low-energy scattering channel that has even particle-exchange parity along the q1D axis, as if the underlying interactions were s-wave. This emergent exchange symmetry is enabled by orbital singlet wave functions in the strongly confined directions, which also confer high-momentum components to low-energy q1D collisions. We measure both the q1D odd-wave and even-wave \"contact\" parameters for the first time, and compare them to theoretical predictions of one-dimensional many-body models. The strength and spatial symmetry of interactions are tuned by a p-wave Feshbach resonance and by transverse confinement strength. Near resonance, the even-wave contact approaches its theoretical unitary value, whereas the maximum observed odd-wave contact remains several orders of magnitude below its unitary limit. Low-energy scattering channels of multi-orbital systems, such as those found here, may provide new routes for the exploration of universal many-body phenomena.

We investigate the scattering properties and bound states of a quasi-two-dimensional (q2D) spin-polarized Fermi gas near a \\(p\\)-wave Feshbach resonance. Strong confinement promotes the out-of-plane spatial wave functions to a discrete, gapped orbital degree of freedom. Exchange-antisymmetric orbital pair wave functions are predicted to give rise to low-energy q2D interactions with \\(s\\)-wave symmetry. Using radiofrequency (rf) spectroscopy, we observe the signature power-law scaling and the dimensional-crossover feature anticipated for the emergent \\(s\\)-wave channel. Additionally, we demonstrate that two types of low-energy dimers, with either \\(s\\)-wave and \\(p\\)-wave symmetry, could be formed via rf spin-flip association from an orbital mixture. These findings illustrate how gapped orbital degrees of freedom can provide additional control over scattering symmetries in strongly confined ultracold gases.

We investigate the scattering properties and bound states of a quasi-two-dimensional (q2D) spin-polarized Fermi gas near a \\(p\\)-wave Feshbach resonance. Strong confinement promotes the out-of-plane spatial wave functions to a discrete, gapped orbital degree of freedom. Exchange-antisymmetric orbital pair wave functions are predicted to give rise to low-energy q2D interactions with \\(s\\)-wave symmetry. Using radiofrequency (rf) spectroscopy, we observe the signature power-law scaling and the dimensional-crossover feature anticipated for the emergent \\(s\\)-wave channel. Additionally, we demonstrate that two types of low-energy dimers, with either \\(s\\)-wave and \\(p\\)-wave symmetry, could be formed via rf spin-flip association from an orbital mixture. These findings illustrate how gapped orbital degrees of freedom can provide additional control over scattering symmetries in strongly confined ultracold gases.

DNA methylation comprises a cumulative record of lifetime exposures superimposed on genetically determined markers. Little is known about methylation dynamics in humans following an acute perturbation, such as infection. We characterized the temporal trajectory of blood epigenetic remodeling in 133 participants in a prospective study of young adults before, during, and after asymptomatic and mildly symptomatic SARS‐CoV‐2 infection. The differential methylation caused by asymptomatic or mildly symptomatic infections was indistinguishable. While differential gene expression largely returned to baseline levels after the virus became undetectable, some differentially methylated sites persisted for months of follow‐up, with a pattern resembling autoimmune or inflammatory disease. We leveraged these responses to construct methylation‐based machine learning models that distinguished samples from pre‐, during‐, and postinfection time periods, and quantitatively predicted the time since infection. The clinical trajectory in the young adults and in a diverse cohort with more severe outcomes was predicted by the similarity of methylation before or early after SARS‐CoV‐2 infection to the model‐defined postinfection state. Unlike the phenomenon of trained immunity, the postacute SARS‐CoV‐2 epigenetic landscape we identify is antiprotective. Synopsis Characterization of the temporal dynamics of blood methylation changes in young adults following asymptomatic and mild SARS‐CoV‐2 infection brings insights into the long‐term memory of environmental exposure and potential disease associations. Both symptomatic and asymptomatic infections induce methylation changes that are not always associated with gene expression changes. Methylation changes persist for longer than gene expression changes. The complex dynamics of methylation alterations can be used to predict the timing of infection. Contrary to the trained immunity phenomenon, the presence of a post‐infection‐like methylation state at baseline is anti‐protective for subsequent SARS‐CoV‐2 infection. Graphical Abstract Characterization of the temporal dynamics of blood methylation changes in young adults following asymptomatic and mild SARS‐CoV‐2 infection brings insights into the long‐term memory of environmental exposure and potential disease associations.

The molecular mechanisms underlying mycorrhizal symbioses, the most ubiquitous and impactful mutualistic plant-microbial interaction in nature, are largely unknown. Through genetic mapping, resequencing and molecular validation, we demonstrate that a G-type lectin receptor-like kinase (lecRLK) mediates the symbiotic interaction between Populus and the ectomycorrhizal fungus Laccaria bicolor. This finding uncovers an important molecular step in the establishment of symbiotic plant-fungal associations and provides a molecular target for engineering beneficial mycorrhizal relationships.