A potential cyanobacterial ancestor of Viridiplantae chloroplasts

The theory envisaging the origin of plastids from endosymbiotic cyanobacteria is well-established but it is difficult to explain the evolution (spread) of plastids in phylogenetically diverse plant groups. It is widely believed that primordial endosymbiosis occurred in the last common ancestor of all algae^1^, which then diverged into the three primary photosynthetic eukaryotic lineages, viz. the Rhodophyta (red algae), Glaucocystophyta (cyanelle-containing algae) and Viridiplantae (green algae plus all land plants)^2^. Members of these three groups invariably have double membrane-bound plastids^3^, a property that endorses the primary endosymbiotic origin of the organelles. On the other hand, the three or four membrane-bound plastids of the evolutionary complicated Chromalveolates [chromista (cryptophytes, haptophytes, and stramenopiles) and alveolata (dinoflagellates, apicomplexans, and ciliates)] are inexplicable in the light of a single endosymbiosis event, thereby necessitating the postulation of the secondary^4,5^ and tertiary^6^ endosymbiosis theories where a nonphotosynthetic protist supposedly engulfed a red or a green alga^7^ and an alga containing a secondary plastid itself was engulfed^8^ respectively. In the current state of understanding, however, there is no clue about the taxonomic identity of the cyanobacterial ancestor of chloroplasts, even though there is a wide consensus on a single primordial endosymbiosis event. During our metagenomic investigation of a photosynthetic geothermal microbial mat community we discovered a novel order-level lineage of Cyanobacteria that - in 16S rRNA gene sequence-based phylogeny - forms a robust monophyletic clade with chloroplast-derived sequences from diverse divisions of Viridiplantae. This cluster diverged deeply from the other major clade encompassing all hitherto known groups of Cyanobacteria plus the chloroplasts of Rhodophyta, Glaucocystophyceae and Chromalveolates. Since this fundamental dichotomy preceded the origin of all chloroplasts, it appears that two early-diverging cyanobacterial lineages had possibly given rise to two discrete chloroplast descents via two separate engulfment events

Quench, thermalization and residual entropy across a non-Fermi liquid to Fermi liquid transition

We study the thermalization, after sudden and slow quenches, of an interacting model having a quantum phase transition from a Sachdev-Ye-Kitaev (SYK) non-Fermi liquid (NFL) to a Fermi liquid (FL). The model has SYK fermions coupled to non-interacting lead fermions and can be realized in a graphene flake connected to external leads. After a sudden quench to the NFL, a thermal state is reached rapidly via collapse-revival oscillations of the quasiparticle residue of the lead fermions. In contrast, the quench to the FL, across the NFL-FL transition, leads to multiple prethermal regimes and much slower thermalization. In the slow quench performed over a time $\tau$, we find that the excitation energy generated has a remarkable intermediate-$\tau$ non-analytic power-law dependence, $\tau^{-\eta}$ with $\eta<1$, which seemingly masks the dynamical manifestation of the initial residual entropy of the SYK fermions. The power-law scaling is expected to eventually break down for $\tau\to\infty$, signaling a violation of adiabaticity, due to the residual entropy present in the SYK fermions

Universal dielectric response across a continuous metal-insulator transition

A wide range of disordered materials, including disordered correlated systems, show universal dielectric response (UDR), followed by a superlinear power-law increase in their optical responses over exceptionally broad frequency regimes. While extensively used in various contexts over the years, the microscopics underpinning UDR remains controversial. Here, we investigate the optical response of the simplest model of correlated fermions, the Falicov-Kimball model, across the continuous metal-insulator transition (MIT) and analyze the associated quantum criticality in detail using cluster extension of dynamical mean-field theory. Surprisingly, we find that UDR naturally emerges in the quantum critical region associated with the continuous MIT. We tie the emergence of these novel features to a many-body orthogonality catastrophe accompanying the onset of strongly correlated electronic glassy dynamics close to the MIT, providing a microscopic realization of Jonscher's time-honored proposal as well as a rationale for similarities in optical responses between correlated electronic matter and canonical glass formers

Pecularities in the distribution of produced particles emission in ²⁴Mg-Ag/Br interactions at 4.5 A GeV*

156-160The angular sub-structures of particle produced within dense and dilute groups along the rapidity axis in 24Mg induced interaction of Ag/Br nuclei in an emulsion detector at 4.5 A GeV/c have been investigated. The experimental results have been compared with the results simulated by Monte Carlo method. Non-statistical jet-like sub-structures have been found in the data. However, when the parameter S2 is used in the analysis there seems to be definite jet-structure for the dilute groups which cannot be accounted for independent emission model (MC). The average behaviour of the S parameters strongly favours the presence of jet-like sub-structures

Prethermalization and wave condensation in a nonlinear disordered Floquet system

8 pages, 4 figures + Supplementary MaterialPeriodically-driven quantum systems make it possible to reach stationary states with new emerging properties. However, this process is notoriously difficult in the presence of interactions because continuous energy exchanges generally boil the system to an infinite temperature featureless state. Here, we describe how to reach nontrivial states in a periodically-kicked Gross-Pitaevskii disordered system. One ingredient is crucial: both disorder and kick strengths should be weak enough to induce sufficiently narrow and well-separated Floquet bands. In this case, inter-band heating processes are strongly suppressed and the system can reach an exponentially long-lived prethermal plateau described by the Rayleigh-Jeans distribution. Saliently, the system can even undergo a wave condensation process when its initial state has a sufficiently low total quasi-energy. These predictions could be tested in nonlinear optical experiments or with ultracold atoms

Prethermalization and wave condensation in a nonlinear disordered Floquet system

8 pages, 4 figures + Supplementary MaterialPeriodically-driven quantum systems make it possible to reach stationary states with new emerging properties. However, this process is notoriously difficult in the presence of interactions because continuous energy exchanges generally boil the system to an infinite temperature featureless state. Here, we describe how to reach nontrivial states in a periodically-kicked Gross-Pitaevskii disordered system. One ingredient is crucial: both disorder and kick strengths should be weak enough to induce sufficiently narrow and well-separated Floquet bands. In this case, inter-band heating processes are strongly suppressed and the system can reach an exponentially long-lived prethermal plateau described by the Rayleigh-Jeans distribution. Saliently, the system can even undergo a wave condensation process when its initial state has a sufficiently low total quasi-energy. These predictions could be tested in nonlinear optical experiments or with ultracold atoms

Quantum critical scaling of the conductivity tensor at the metal-insulator transition in Nb1−x_{1-x}Tix_{x}N

5 pages, 3 figuresIn contrast to the Landau paradigm, a metal-insulator transition (MIT), driven purely by competition between itinerance and localization and unaccompanied by any conventional (e.g, magnetic) order-disorder instabilities, admits no obvious local order parameter. Here, we present a detailed analysis of the quantum criticality in magneto-transport data on the alloy Nb$_{1-x}$Ti$_{x}$N across a Ti-doping-driven a MIT. We demonstrate, for the first time, clear and novel quantum criticality reflected in the full conductivity tensor across the MIT. Wide ranging, comprehensive accord with recent theoretical predictions strongly suggests that these unanticipated findings are representative of a continuous MIT of the band-splitting type, rather than a conventional Anderson disorder or a "pure" correlation-driven first-order Mott type

Quantum critical scaling of the conductivity tensor at the metal-insulator transition in Nb1−x_{1-x}Tix_{x}N

5 pages, 3 figuresIn contrast to the Landau paradigm, a metal-insulator transition (MIT), driven purely by competition between itinerance and localization and unaccompanied by any conventional (e.g, magnetic) order-disorder instabilities, admits no obvious local order parameter. Here, we present a detailed analysis of the quantum criticality in magneto-transport data on the alloy Nb$_{1-x}$Ti$_{x}$N across a Ti-doping-driven a MIT. We demonstrate, for the first time, clear and novel quantum criticality reflected in the full conductivity tensor across the MIT. Wide ranging, comprehensive accord with recent theoretical predictions strongly suggests that these unanticipated findings are representative of a continuous MIT of the band-splitting type, rather than a conventional Anderson disorder or a "pure" correlation-driven first-order Mott type