Spectral signatures of vibronic coupling in trapped cold atomic Rydberg systems

Atoms and ions confined with electric and optical fields form the basis of many current quantum simulation and computing platforms. When excited to high-lying Rydberg states, long-ranged dipole interactions emerge which strongly couple the electronic and vibrational degrees of freedom through state-dependent forces. This vibronic coupling and the ensuing hybridization of internal and external degrees of freedom manifest through clear signatures in the many-body spectrum. We illustrate this by considering the case of two trapped Rydberg ions, for which the interaction between the relative vibrations and Rydberg states realizes a quantum Rabi model. We proceed to demonstrate that the aforementioned hybridization can be probed by radio frequency spectroscopy and discuss observable spectral signatures at finite temperatures and for larger ion crystals.Comment: 6 + 12 pages, 4 figure

Non-equilibrium dynamics of bulk-deterministic cellular automata

In this thesis we study simple one-dimensional nonequilibirum many-body systems, namely, reversible cellular automata (RCA). These are discrete time lattice models exhibiting emergent collective excitations---solitons---that move with fixed velocities and that interact via pairwise scattering. In particular, we study the attractively interacting Rule 201 RCA and noninteracting Rule 150 RCA which, together with the extensively studied repulsively interacting Rule 54 RCA constitute arguably the simplest one-dimensional microscopic physical models of strongly interacting and asymptotically freely propagating particles, to investigate interacting nonequilibrium many-body dynamics. After a brief literature review of the field, we present the first publication-style chapter which considers the Rule 201 RCA. Here, we study the stationary or steady state properties of systems with periodic, deterministic, and stochastic boundary conditions. We demonstrate that, despite the complexities of the model, specifically, a reducible state space and nontrivial topological vacuum, the model exhibits a simple and intuitive quasiparticle interpretation, reminiscent of the simpler Rule 54 RCA. This enables us to obtain exact expressions for the steady states in terms of a highly versatile matrix product state (MPS) representation that takes an instructive generalized Gibbs ensemble form. In the second publication-style chapter, we study the Rule 150 RCA. Due to its simplicity, originating from the noninteracting dynamics, we are able to obtain many exact results relating to its dynamics. To start, we generalize the MPS ansatz used to study the Rule 201 RCA, and find its exact steady state distribution for identical boundary conditions. We proceed to extend the MPS ansatz further and obtain a class of eigenvectors that form the dominant decay modes of the Markov propagator. Following this, we postulate a conjecture for the complete spectrum, which is in perfect agreement with numerics obtained via exact diagonalization of computationally tractable system sizes, providing access to the full relaxation dynamics. From here, we further utilise the ansatz to investigate the large deviation statistics and obtain exact expressions for its scaled cumulant generating function and rate function, which demonstrate the existence of a dynamical first order phase transition. The third and final publication-style chapter focuses on the exact dynamical large deviations statistics of the Rule 201 RCA. Specifically, we employ the methods introduced to study the large deviations of the Rule 54 RCA and show that they fail here to provide any insight into the atypical dynamical behaviour of the Rule 201 RCA. We suggest that this is due to the restrictions imposed by the local dynamical rules, which limits the support of the local observables. In spite of this, we explicitly derived an exact analytic expression for the dominant eigenvalue of the tilted Markov propagator, from which several large deviation statistics can be obtained

Non-equilibrium dynamics of bulk-deterministic cellular automata

In this thesis we study simple one-dimensional nonequilibirum many-body systems, namely, reversible cellular automata (RCA). These are discrete time lattice models exhibiting emergent collective excitations---solitons---that move with fixed velocities and that interact via pairwise scattering. In particular, we study the attractively interacting Rule 201 RCA and noninteracting Rule 150 RCA which, together with the extensively studied repulsively interacting Rule 54 RCA constitute arguably the simplest one-dimensional microscopic physical models of strongly interacting and asymptotically freely propagating particles, to investigate interacting nonequilibrium many-body dynamics. After a brief literature review of the field, we present the first publication-style chapter which considers the Rule 201 RCA. Here, we study the stationary or steady state properties of systems with periodic, deterministic, and stochastic boundary conditions. We demonstrate that, despite the complexities of the model, specifically, a reducible state space and nontrivial topological vacuum, the model exhibits a simple and intuitive quasiparticle interpretation, reminiscent of the simpler Rule 54 RCA. This enables us to obtain exact expressions for the steady states in terms of a highly versatile matrix product state (MPS) representation that takes an instructive generalized Gibbs ensemble form. In the second publication-style chapter, we study the Rule 150 RCA. Due to its simplicity, originating from the noninteracting dynamics, we are able to obtain many exact results relating to its dynamics. To start, we generalize the MPS ansatz used to study the Rule 201 RCA, and find its exact steady state distribution for identical boundary conditions. We proceed to extend the MPS ansatz further and obtain a class of eigenvectors that form the dominant decay modes of the Markov propagator. Following this, we postulate a conjecture for the complete spectrum, which is in perfect agreement with numerics obtained via exact diagonalization of computationally tractable system sizes, providing access to the full relaxation dynamics. From here, we further utilise the ansatz to investigate the large deviation statistics and obtain exact expressions for its scaled cumulant generating function and rate function, which demonstrate the existence of a dynamical first order phase transition. The third and final publication-style chapter focuses on the exact dynamical large deviations statistics of the Rule 201 RCA. Specifically, we employ the methods introduced to study the large deviations of the Rule 54 RCA and show that they fail here to provide any insight into the atypical dynamical behaviour of the Rule 201 RCA. We suggest that this is due to the restrictions imposed by the local dynamical rules, which limits the support of the local observables. In spite of this, we explicitly derived an exact analytic expression for the dominant eigenvalue of the tilted Markov propagator, from which several large deviation statistics can be obtained

On the Enhanced Interstellar Scattering Toward B1849+005

(Abridged) This paper reports new Very Large Array (VLA) and Very Long Baseline Array (VLBA) observations of the extragalactic source B1849+005 at frequencies between 0.33 and 15 GHz and the re-analysis of archival VLA observations at 0.33, 1.5, and 4.9 GHz. The structure of this source is complex but interstellar scattering dominates the structure of the central component at least to 15 GHz. An analysis of the phase structure functions of the interferometric visibilities shows the density fluctuations along this line of sight to be anisotropic (axial ratio = 1.3) with a frequency-independent position angle, and having an inner scale of roughly a few hundred kilometers. The anisotropies occur on length scales of order 10^{15} cm (D/5 kpc), which within the context of certain magnetohydrodynamic turbulence theories indicates the length scale on which the kinetic and magnetic energy densities are comparable. A conservative upper limit on the velocity of the scattering material is 1800 km/s. In the 0.33 GHz field of view, there are a number of other sources that might also be heavily scattered. Both B1849+005 and PSR B1849+00 are highly scattered, and they are separated by only 13'. If the lines of sight are affected by the same ``clump'' of scattering material, it must be at least 2.3 kpc distant. However, a detailed attempt to account for the scattering observables toward these sources does not produce a self-consistent set of parameters for such a clump. A clump of H\alpha emission, possibly associated with the H II region G33.418-0.004, lies between these two lines of sight, but it seems unable to account for all of the required excess scattering.Comment: 23 pages, LaTeX2e AASTeX, 13 figures in 14 PostScript files, accepted for publication in Ap

Anomalous Radio-Wave Scattering from Interstellar Plasma Structures

This paper considers scattering screens that have arbitrary spatial variations of scattering strength transverse to the line of sight, including screens that are spatially well confined, such as disks and filaments. We calculate the scattered image of a point source and the observed pulse shape of a scattered impulse. The consequences of screen confinement include: (1) Source image shapes that are determined by the physical extent of the screen rather than by the shapes of much-smaller diffracting microirregularities. These include image elongations and orientations that are frequency dependent. (2) Variation with frequency of angular broadening that is much weaker than the trademark \nu^{-2} scaling law (for a cold, unmagnetized plasma), including frequency-independent cases; and (3) Similar departure of the pulse broadening time from the usually expected \nu^{-4} scaling law. We briefly discuss applications that include scattering of pulses from the Crab pulsar by filaments in the Crab Nebula; image asymmetries from Galactic scattering of the sources Cyg X-3, Sgr A*, and NGC 6334B; and scattering of background active galactic nuclei by intervening galaxies. We also address the consequences for inferences about the shape of the wavenumber spectrum of electron density irregularities, which depend on scaling laws for the image size and the pulse broadening. Future low-frequency (< 100 MHz) array observations will also be strongly affected by the Galactic structure of scattering material. Our formalism is derived in the context of radio scattering by plasma density fluctuations. It is also applicable to optical, UV and X-ray scattering by grains in the interstellar medium.Comment: 21 pages, LaTeX2e with AASTeX-4.0, 6 PostScript figures, accepted by ApJ, revised version has minor changes to respond to referee comments and suggestion

Multi-frequency VLBA Observations of the Compact Double B2 2050+36: Constraints on Interstellar Scattering Revisited

We present multi-frequency observations with the Very Long Baseline Array of the compact double radio source B2 2050+36. Our observations are at 0.33, 0.61, 1.67, 2.3, and 8.4 GHz, with the 0.61 GHz observations forming the third epoch of observation of this source at that frequency. At 0.61 GHz, the structure of B2 2050+36 is dominated by two components 56 mas apart. Within the uncertainties of the various measurements, this separation has remained unchanged for the past 16 years. Any differential image wander caused by refractive interstellar scattering is less than 4 mas. Both the lack of differential image wander and the frequency dependence of the angular diameter of B2 2050+36 below 1 GHz indicate that the electron density power spectrum along this line of sight has a spectral index near the Kolmogorov value, with a value of 4 being highly unlikely. We conclude that diffractive scattering dominates along this line of sight; results in the literature indicate that this conclusion also holds true for the line of sight to the pulsar PSR B2020+28 (8.7 deg. from B2 2050+36). Comparison of our 1.67 GHz observations with those obtained 21 years previously place a limit on the projected linear separation velocity of the two components of c.Comment: 19 pages LaTeX2e with AASTeX 5, 3 figures in 7 PostScript files; accepted for publication in the Ap

Search for Nanosecond Optical Pulses from Nearby Solar‐Type Stars

With "Earth 2000" technology we could generate a directed laser pulse that outshines the broadband visible light of the Sun by 4 orders of magnitude. This is a conservative lower bound for the technical capability of a communicating civilization; optical interstellar communication is thus technically plausible. We have built a pair of systems to detect nanosecond pulsed optical signals from a target list that includes some 13,000 Sun-like stars, and we have made some 16,000 observations totaling nearly 2400 hr during five years of operation. A beam splitter-fed pair of hybrid avalanche photodetectors at the 1.5 m Wyeth Telescope at the Harvard/Smithsonian Oak Ridge Observatory (Agassiz Station) triggers on a coincident pulse pair, initiating measurement of pulse width and intensity at subnanosecond resolution. An identical system at the 0.9 m Cassegrain at Princeton's Fitz-Randolph Observatory performs synchronized observations with 0.1 μs event timing, permitting unambiguous identification of even a solitary pulse. Among the 11,600 artifact-free observations at Harvard, the distribution of 274 observed events shows no pattern of repetition, and is consistent with a model with uniform event rate, independent of target. With one possible exception (HIP 107395), no valid event has been seen simultaneously at the two observatories. We describe the search and candidate events and set limits on the prevalence of civilizations transmitting intense optical pulses

Hepatocellular Carcinoma Masquerading as a Large Renal Mass with Hepatic Invasion

Large masses are evaluated with imaging to assess primary origin and tumor spread. We present the unusual case of a 53-year-old male with a 17-cm right upper quadrant mass suspected to be renal or adrenal in origin based on radiographic findings. After surgical excision, the mass was subsequently discovered to be primary hepatocellular carcinoma with direct extension to the kidney and adrenal gland. A diagnosis of chronic hepatitis B was made postoperatively. Primary hepatocellular carcinoma with direct renal extension is an exceedingly rare occurrence based on our experience and review of the published literature

Dietary Protein to Support Anabolism with Resistance Exercise in Young Men

Resistance exercise is fundamentally anabolic and as such stimulates the process of skeletal muscle protein synthesis (MPS) in an absolute sense and relative to skeletal muscle protein breakdown (MPB). However, the net effect of resistance exercise is to shift net protein balance (NPB ϭ MPS Ϫ MPB) to a more positive value; however, in the absence of feeding NPB remains negative. Feeding stimulates MPS to an extent where NPB becomes positive, for a transient time. When combined, resistance exercise and feeding synergistically interact to result in NPB being greater than with feeding alone. This feeding-and exercise-induced stimulation of NPB is what, albeit slowly, results in muscle hypertrophy. With this rudimentary knowledge we are now at the point where we can manipulate variables within the system to see what impact these interventions have on the processes of MPS, MPB, and NPB and ultimately and perhaps most importantly, muscle hypertrophy and strength. We used established models of skeletal muscle amino acid turnover to examine how protein source (milk versus soy) acutely affects the processes of MPS and MPB after resistance exercise. Our findings revealed that even when balanced quantities of total protein and energy are consumed that milk proteins are more effective in stimulating amino acid uptake and net protein deposition in skeletal muscle after resistance exercise than are hydrolyzed soy proteins. Importantly, the finding of increased amino acid uptake would be independent of the differences in amino acid composition of the two proteins. We propose that the improved net protein deposition with milk protein consumption is also not due to differences in amino acid composition, but is due to a different pattern of amino acid delivery associated with milk versus hydrolyzed soy proteins. If our acute findings are accurate then we hypothesized that chronically the greater net protein deposition associated with milk protein consumption post-resistance exercise would eventually lead to greater net protein accretion (i.e., muscle fiber hypertrophy), over a longer time period. In young men completing 12 weeks of resistance training (5d/wk) we observed a tendency (P ϭ 0.11) for greater gains in whole body lean mass and whole as greater muscle fiber hypertrophy with consumption of milk. While strength gains were not different between the soy and milk-supplemented groups we would argue that the true significance of a greater increase in lean mass that we observed with milk consumption may be more important in groups of persons with lower initial lean mass and strength such as the elderly. Key teaching points: • Resistance exercise is fundamentally anabolic; as such it stimulates MPS which pushes muscle NPB in a more positive direction. • Muscle NPB becomes positive, only when amino acids are provided to muscle (i.e., protein or amino acids are consumed). • After resistance exercise, the consumption of protein results in an increase in MPS that is greater than consumption of protein alone; this is due to synergistic stimulation of MPS by amino acids and exercise, which appear to be acting through different signalling pathways. • Over time the synergistic combination of amino acid feeding and resistance exercise results in accretion of muscle proteinsmuscle hypertrophy. • Protein source acutely affects muscle amino acid uptake and NPB following resistance exercise in a manner that appears to be related not to amino acid composition but to the pattern of amino acid delivery to peripheral tissues. In this regard, milk proteins are more effective at supporting protein accretion than are soy proteins. • The ability of milk to support muscle protein accretion may have greater relevance in populations with compromised muscle mass

Finding Radio Pulsars in and Beyond the Galactic Center

Radio-wave scattering is enhanced dramatically for Galactic center sources in a region with radius >~ 15 arc min. Using scattering from Sgr A* and other sources, we show that pulse broadening for pulsars in the Galactic center is {\em at least} 6.3 \nu^{-4} seconds (\nu = radio frequency in GHz) and is most likely 50--200 times larger because the relevant scattering screen appears to be within the Galactic center region itself. Pulsars beyond---but viewed through---the Galactic center suffer even greater pulse broadening and are angularly broadened by <~ 2 {\em arc min}. Periodicity searches at radio frequencies are likely to find only long period pulsars and, then, only if optimized by using frequencies >~ 7 GHz and by testing for small numbers of harmonics in the power spectrum. The optimal frequency is $\nu ~ 7.3 GHz (\Delta_{0.1}P\sqrt{\alpha})^{-1/4}$ where \Delta_{0.1} is the distance of the scattering region from Sgr A* in units of 0.1 kpc, P is the period (seconds), and \alpha is the spectral index. A search for compact sources using aperture synthesis may be far more successful than searches for periodicities because the angular broadening is not so large as to desensitize the survey. We estimate that the number of {\em detectable} pulsars in the Galactic center may range from <= 1 to 100, with the larger values resulting from recent, vigorous starbursts. Such pulsars provide unique opportunities for probing the ionized gas, gravitational potential, and stellar population near Sgr A*.Comment: 13 pages, 4 PS figures, LaTeX and requires AASTeX macro aas2pp4, accepted by ApJ, also available as http://astrosun.tn.cornell.edu/SPIGOT/papers/pulsar/gc_psr.web