Identical Timescales Research Articles

Quantum nature of black holes: fast scrambling versus echoes

Two seemingly distinct notions regarding black holes have captured the imagination of theoretical physicists over the past decade: first, black holes are conjectured to be fast scramblers of information, a notion that is further supported through connections to quantum chaos and decay of mutual information via AdS/CFT holography. Second, black hole information paradox has motivated exotic quantum structure near horizons of black holes (e.g., gravastars, fuzzballs, or firewalls) that may manifest themselves through delayed gravitational wave echoes in the aftermath of black hole formation or mergers, and are potentially observable by LIGO/Virgo observatories. By studying various limits of charged AdS/Schwarzschild black holes we show that, if properly defined, the two seemingly distinct phenomena happen on an identical timescale of log(Radius)/(π × Temperature). We further comment on the physical interpretation of this coincidence and the corresponding holographic interpretation of black hole echoes.

Strong modification of the transport level alignment in organic materials after optical excitation

Organic photovoltaic devices operate by absorbing light and generating current. These two processes are governed by the optical and transport properties of the organic semiconductor. Despite their common microscopic origin—the electronic structure—disclosing their dynamical interplay is far from trivial. Here we address this issue by time-resolved photoemission to directly investigate the correlation between the optical and transport response in organic materials. We reveal that optical generation of non-interacting excitons in a fullerene film results in a substantial redistribution of all transport levels (within 0.4 eV) of the non-excited molecules. As all observed dynamics evolve on identical timescales, we conclude that optical and transport properties are completely interlinked. This finding paves the way for developing novel concepts for transport level engineering on ultrafast time scales that could lead to novel functional optoelectronic devices.

Corrole-ferrocene and corrole-anthraquinone dyads: synthesis, spectroscopy and photochemistry.

Two different donor-acceptor systems based on corrole-ferrocene and corrole-anthraquinone having the 'Olefin Bridge' at the β-pyrrole position have been designed and synthesized. Both the dyads corrole-ferrocene () and corrole-anthraquinone () are characterized by elemental analysis, ESI-MS, (1)H NMR, UV-Visible, fluorescence spectroscopies (steady-state, femtosecond time-resolved), femtosecond transient absorption spectroscopy (fs-TA) and electrochemical methods. (1)H-NMR shows that two doublets at 6.50 and 7.25(δ) ppm belong to vinylic protons, which are characteristic of the formation of dyads. UV-Visible absorption spectra showed that dyads are merely superpositions of their respective constituent monomers and dominated by corrole S1 ← S0 (Q-band) and S2 ← S0 (Soret band) transitions with a systematic red-shift of both Soret and Q-bands along with the broadening of the bands. A prominent splitting of the Soret band for both the dyads is observed due to bulky substitutions at the peripheral position, which deviate from the planarity of the corrole macrocycle. Both the dyads exhibit significant fluorescence emission quenching (95-97%) of corrole emission compared to the free-base corrole monomer. Emission quenching is attributed to the excited-state intramolecular photoinduced electron transfer (PET) from corrole to anthraquinone in the dyad, whereas in the dyad it is reversed. The electron-transfer rates (kET) for and were found to be 3.33 × 10(11) and 2.78 × 10(10) s(-1), respectively. Despite their very different driving forces, charge separation (CS) and charge recombination (CR) are found to be in identical timescales.

Semiparametric efficient inferences for lifetime regression model with time-dependent covariates

Through a threshold equation, we propose a time-transformed accelerated failure time (AFT) model with time-dependent covariate history in survival analysis. This model contains a general class of semiparametric lifetime regression models, including AFT with identical time-scale and a wide spectrum of Cox’s hazard regression models and their frailty variants. We first construct the semiparametric efficient statistical inferences on the AFT model with identical time-scale. The theoretical semiparametric Fisher information bound is explicitly derived under right-censored data setting. And the overidentified estimating equation (OEE) approach based on two martingale processes is shown to achieve this semiparametric efficiency bound. Extensions of the semiparametric efficient statistical inferences to the time-transformed AFT versions are also discussed. We also conclude that most log-rank estimating equations would suffer severe information loss primarily caused by wiggling pattern of the baseline hazard function, while the OEE approach can alleviate the damaging effects. A simulated biological life history example is numerically studied.

Primary processes underlying the photostability of isolated DNA bases: adenine.

The UV chromophores in DNA are the nucleic bases themselves, and it is their photophysics and photochemistry that govern the intrinsic photostability of DNA. Because stability is related to the conversion of dangerous electronic to less-dangerous vibrational energy, we study ultrafast electronic relaxation processes in the DNA base adenine. We excite adenine, isolated in a molecular beam, to its pipi* state and follow its relaxation dynamics using femtosecond time-resolved photoelectron spectroscopy. To discern which processes are important on which timescales, we compare adenine with 9-methyl adenine. Methylation blocks the site of the much-discussed pisigma* state that had been thought, until now, minor. Time-resolved photoelectron spectroscopy reveals that, although adenine and 9-methyl adenine show almost identical timescales for the processes involved, the decay pathways are quite different. Importantly, we confirm that in adenine at 267-nm excitation, the pisigma* state plays a major role. We discuss these results in the context of recent experimental and theoretical studies on adenine, proposing a model that accounts for all known results, and consider the relationship between these studies and electron-induced damage in DNA.

Early Cretaceous geomagnetic behaviour compared to a computer model

Twelve patterns of geomagnetic dipole behaviour, recurring five times, are recorded in a 88 m bore-core penetrating some 3.2 Ma of shallow water carbonates around 127 Ma (Early Cretaceous of Southern Italy). Each pattern sequence represents a complete reversal cycle that lasts for c. 660 ka, formed of c. 300 ka of predominantly normal polarity and c. 330 ka of mainly reversed polarity. Virtual Geomagnetic Pole (VGP) excursions, mostly lasting 5–25 ka, are initially of lower amplitude; these become increasingly common and of larger amplitude until a reversal is completed. The succession of excursions, within the reversed sequences, appears to occur as harmonics of about 20, 44 and 64 ka. These are comparable to the Earth's orbital frequencies (precession and obliquity). Long-term orbital eccentricity cycles have been identified in the intensity of oceanic magnetic anomalies of the same age (Iorio, M., Tarling, D.H., D'Argenio, B. 1998b, Periodicity of magnetic intensities in magnetic anomaly profiles: the Cretaceous of the Central Pacific. Geophysical Journal International 133, 233–244). Geomagnetic behaviour predicted from 3-D computer simulations by Glatzmaier et al. (Glatzmaier, G.A., Coe, R.S., Hongre, L., Roberts, P.H., 1999. The role of the Earth's mantle in controlling the frequency of geomagnetic reversals. Nature 401, 885–890), based on the geophysical properties of the present-day core-mantle boundary, has very close similarities to that observed in the bore-core remanence. In particular, oscillations in the location and intensity of the computed geomagnetic dipole occur on almost identical time-scales to those previously determined for the bore-core VGP and intensity.