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Articles 31 - 60 of 87
Full-Text Articles in Physical Sciences and Mathematics
Discovery Of An Unusual Optical Transient With The Hubble Space Telescope, K Barbary, Ks Dawson, K Tokita, G Aldering, R Amanullah, Nv Connolly, M Doi, L Faccioli, V Fadeyev, As Fruchter, G Goldhaber, A Goobar, A Gude, Xiaosheng Xiaosheng Huang, Y Ihara, K Konishi, M Kowalski, C Lidman, J Meyers, T Morokuma, P Nugent, S Perlmutter, D Rubin, D Schlegel, Al Spadafora, N Suzuki, Hk Swift, N Takanashi, Rc Thomas, N Yasuda, Supernova Cosmology Project
Discovery Of An Unusual Optical Transient With The Hubble Space Telescope, K Barbary, Ks Dawson, K Tokita, G Aldering, R Amanullah, Nv Connolly, M Doi, L Faccioli, V Fadeyev, As Fruchter, G Goldhaber, A Goobar, A Gude, Xiaosheng Xiaosheng Huang, Y Ihara, K Konishi, M Kowalski, C Lidman, J Meyers, T Morokuma, P Nugent, S Perlmutter, D Rubin, D Schlegel, Al Spadafora, N Suzuki, Hk Swift, N Takanashi, Rc Thomas, N Yasuda, Supernova Cosmology Project
Physics and Astronomy
We present observations of SCP 06F6, an unusual optical transient discovered during the Hubble Space Telescope Cluster Supernova Survey. The transient brightened over a period of ~;;100 days, reached a peak magnitude of ~;;21.0 in both i_775 and z_850, and then declined over a similar timescale. There is no host galaxy or progenitor star detected at the location of the transient to a 3 sigma upper limit of i_775 = 26.4 and z_850 = 26.1, giving a corresponding lower limit on the flux increase of a factor of ~;;120. Multiple spectra show five broad absorption bands between 4100 AA and …
An Intensive Hst Survey For Z>1 Supernovae By Targeting Galaxy Clusters, K S. Dawson, G Aldering, R Amanullah, K Barbary, L F. Barrientos, M Brodwin, N Connolly, A Dey, M Doi, M Donahue, P Eisenhardt, E Ellingson, L Faccioli, V Fadeyev, H K. Fakhouri, A S. Fruchter, D G. Gilbank, M D. Gladders, G Goldhaber, A H. Gonzalez, A Goobar, A Gude, T Hattori, H Hoekstra, Xiaosheng Huang, Y Ihara, B T. Jannuzi, D Johnston, K Kashikawa, B Koester, K Konishi, M Kowalski, C Lidman, E V. Linder, L Lubin, J Meyers, T Morokuma, F Munshi, C Mullis, T Oda, N Panagia, S Perlmutter, M Postman, T Pritchard, J Rhodes, P Rosati, D Rubin, D J. Schlegel, A Spadafora, S A. Stanford, V Stanishev, D Stern, M Strovink, N Suzuki, N Takanashi, K Tokita, M Wagner, L Wang, N Yasuda, H. K. C. Yee, Supernova Cosmology Project
An Intensive Hst Survey For Z>1 Supernovae By Targeting Galaxy Clusters, K S. Dawson, G Aldering, R Amanullah, K Barbary, L F. Barrientos, M Brodwin, N Connolly, A Dey, M Doi, M Donahue, P Eisenhardt, E Ellingson, L Faccioli, V Fadeyev, H K. Fakhouri, A S. Fruchter, D G. Gilbank, M D. Gladders, G Goldhaber, A H. Gonzalez, A Goobar, A Gude, T Hattori, H Hoekstra, Xiaosheng Huang, Y Ihara, B T. Jannuzi, D Johnston, K Kashikawa, B Koester, K Konishi, M Kowalski, C Lidman, E V. Linder, L Lubin, J Meyers, T Morokuma, F Munshi, C Mullis, T Oda, N Panagia, S Perlmutter, M Postman, T Pritchard, J Rhodes, P Rosati, D Rubin, D J. Schlegel, A Spadafora, S A. Stanford, V Stanishev, D Stern, M Strovink, N Suzuki, N Takanashi, K Tokita, M Wagner, L Wang, N Yasuda, H. K. C. Yee, Supernova Cosmology Project
Physics and Astronomy
We present a new survey strategy to discover and study high redshift Type Ia supernovae (SNe Ia) using the Hubble Space Telescope (HST). By targeting massive galaxy clusters at 0.9<zHST field survey and a factor of three improvement in the total yield of SN detections in relatively dust-free red-sequence galaxies. In total, sixteen SNe were discovered at z>0.95, nine of which were in galaxy clusters. This strategy provides a SN sample that can be used to decouple the effects of host galaxy extinction and intrinsic color in high redshift SNe, thereby reducing one of the …
Hubble Space Telescope Discovery Of A Z = 3.9 Multiply Imaged Galaxy Behind The Complex Cluster Lens Warps J1415.1+36 At Z = 1.026, Xiaosheng Huang, T Morokuma, Hk Fakhouri, G Aldering, R Amanullah, K Barbary, M Brodwin, Nv Connolly, Ks Dawson, M Doi, L Faccioli, V Fadeyev, As Fruchter, G Goldhaber, Md Gladders, Jf Hennawi, Y Ihara, Mj Jee, M Kowalski, K Konishi, C Lidman, J Meyers, La Moustakas, S Perlmutter, D Rubin, Dj Schlegel, Al Spadafora, N Suzuki, N Takanashi, N Yasuda
Hubble Space Telescope Discovery Of A Z = 3.9 Multiply Imaged Galaxy Behind The Complex Cluster Lens Warps J1415.1+36 At Z = 1.026, Xiaosheng Huang, T Morokuma, Hk Fakhouri, G Aldering, R Amanullah, K Barbary, M Brodwin, Nv Connolly, Ks Dawson, M Doi, L Faccioli, V Fadeyev, As Fruchter, G Goldhaber, Md Gladders, Jf Hennawi, Y Ihara, Mj Jee, M Kowalski, K Konishi, C Lidman, J Meyers, La Moustakas, S Perlmutter, D Rubin, Dj Schlegel, Al Spadafora, N Suzuki, N Takanashi, N Yasuda
Physics and Astronomy
We report the discovery of a multiply lensed Ly Alpha (Lya) emitter at z = 3.90 behind the massive galaxy cluster WARPS J1415.1+3612 at z = 1.026. Images taken by the Hubble Space Telescope(HST) using ACS reveal a complex lensing system that produces a prominent, highly magnified arc and a triplet of smaller arcs grouped tightly around a spectroscopically confirmed cluster member. Spectroscopic observations using FOCAS on Subaru confirm strong Lya emission in the source galaxy and provide redshifts for more than 21 cluster members, from which we obtain a velocity dispersion of 807+/-185 km/s. Assuming a singular isothermal sphere …
Contribution Of A Portable Air Plasma Torch To Rapid Blood Coagulation As A Method Of Preventing Bleeding, Kuo S. P., O. Tarasenko, J. Chang, S. Popović, C. Y. Chen, H. W. Fan, A. Scott, M. Lahiani, P. Alusta, J. D. Drake, Milka Nikolic
Contribution Of A Portable Air Plasma Torch To Rapid Blood Coagulation As A Method Of Preventing Bleeding, Kuo S. P., O. Tarasenko, J. Chang, S. Popović, C. Y. Chen, H. W. Fan, A. Scott, M. Lahiani, P. Alusta, J. D. Drake, Milka Nikolic
Physics and Astronomy
The effectiveness and mechanism of a low temperature air plasma torch in clotting blood are explored. Both blood droplets and smeared blood samples were used in the tests. The treated droplet samples reveal how blood clotting depends on the distance at which the torch operated, and for how long the droplets have been exposed to the torch. Microscopy and cell count of smeared blood samples shed light on dependencies of erythrocyte and platelet counts on torch distance and exposure time. With an increase of torch distance, the platelet count of treated blood samples increases but is less than that of …
Controlled Compositional Disorder In Er3+:Y2sio5 Provides A Wide-Bandwidth Spectral Hole Burning Material At 1.5mum, Thomas Böttger, C W. Thiel, R L. Cone, Y Sun
Controlled Compositional Disorder In Er3+:Y2sio5 Provides A Wide-Bandwidth Spectral Hole Burning Material At 1.5mum, Thomas Böttger, C W. Thiel, R L. Cone, Y Sun
Physics and Astronomy
The subgigahertz spectral bandwidth of the lowest energy 1.5mum Er3+ I15/24-->I13/24 optical transition in Er3+:Y2SiO5 has been increased to ˜22GHz by intentionally introducing compositional disorder through codoping with Eu3+ impurity ions. This illustrates a general bandwidth control technique for spectral hole burning device applications including spatial-spectral holography and quantum computing. Coherence measurements by stimulated photon echoes demonstrated that the increased disorder does not perturb the dynamical properties of the Er3+ transition and, thus, gives the desired bandwidth enhancement without penalty in other properties. The echo measurements and model analysis also show …
Magnetic G Tensors For The I 15/2 4 And I 13/2 4 States Of Er3+: Y2 Si O5, Y Sun, Thomas Böttger, C W. Thiel, R L. Cone
Magnetic G Tensors For The I 15/2 4 And I 13/2 4 States Of Er3+: Y2 Si O5, Y Sun, Thomas Böttger, C W. Thiel, R L. Cone
Physics and Astronomy
We present the complete Zeeman g tensors for the lowest-energy I15∕24 and I13∕24 states of Er3+ doped into Y2SiO5 for both crystallographic sites deduced from orientation-dependent optical Zeeman spectroscopy over three orthogonal crystal planes. From these data, principal axes of the g tensors were determined for each crystallographic site. Along axes with maximum values, the effective g factors are 14.65 (site 1) and 15.46 (site 2) for the ground state, and 12.97 (site 1) and 13.77 (site 2) for the excited state. To minimize optical decoherence and spectral diffusion in device applications and high resolution spectroscopy, special directions for applying …
Constraints On First-Light Ionizing Sources From Optical Depth Of The Cosmic Microwave Background, J Shull, Aparna Venkatesan
Constraints On First-Light Ionizing Sources From Optical Depth Of The Cosmic Microwave Background, J Shull, Aparna Venkatesan
Physics and Astronomy
We examine the constraints on high-redshift star formation, ultraviolet and X-ray preionization, and the epoch of reionization at redshift zr, inferred from the recent WMAP-5 measurement, τe = 0.084 ± 0.016, of the electron- scattering optical depth of the cosmic microwave background (CMB). Half of this scattering can be accounted for by the optical depth, τe = 0.04-0.05, of a fully ionized intergalactic medium (IGM) at z ≤ zGP ≈ 6-7, consistent with Gunn-Peterson absorption in neutral hydrogen. The required additional optical depth, Δτe = 0.03 ± 0.02 atz > zGP, …
From Morphology To Neural Information: The Electric Sense Of The Skate, Marcelo Camperi, Timothy C. Tricas, Brandon R. Brown
From Morphology To Neural Information: The Electric Sense Of The Skate, Marcelo Camperi, Timothy C. Tricas, Brandon R. Brown
Physics and Astronomy
Morphology typically enhances the fidelity of sensory systems. Sharks, skates, and rays have a well-developed electrosense that presents strikingly unique morphologies. Here, we model the dynamics of the peripheral electrosensory system of the skate, a dorsally flattened batoid, moving near an electric dipole source (e.g., a prey organism). We compute the coincident electric signals that develop across an array of the skate's electrosensors, using electrodynamics married to precise morphological measurements of sensor location, infrastructure, and vector projection. Our results demonstrate that skate morphology enhances electrosensory information. Not only could the skate locate prey using a simple population vector algorithm, but …
Optical Decoherence And Spectral Diffusion At 1.5 Μm In Er3+: Y2 Sio5 Versus Magnetic Field, Temperature, And Er3+ Concentration, Thomas Böttger, C W. Thiel, Y Sun, R L. Cone
Optical Decoherence And Spectral Diffusion At 1.5 Μm In Er3+: Y2 Sio5 Versus Magnetic Field, Temperature, And Er3+ Concentration, Thomas Böttger, C W. Thiel, Y Sun, R L. Cone
Physics and Astronomy
The mechanisms and effects of spectral diffusion for optical transitions of paramagnetic ions have been explored using the inhomogeneously broadened 1536 nm I15∕24→I13∕24 transition in Er3+:Y2SiO5. Using photon echo spectroscopy, spectral diffusion was measured by observing the evolution of the effective coherence lifetimes over time scales from 1μs to 20 ms for magnetic-field strengths from 0.3 to 6.0 T, temperatures from 1.6 to 6.5 K, and nominal Er3+ concentrations of 0.0015%, 0.005%, and 0.02%. To understand the effect of spectral diffusion on material decoherence for different environmental conditions and material compositions, data and models were compared to identify spectral diffusion …
Spectroscopy And Dynamics Of Er3+: Y2 Si O5 At 1.5 Μm, Thomas Böttger, Y Sun, C W. Thiel, R L. Cone
Spectroscopy And Dynamics Of Er3+: Y2 Si O5 At 1.5 Μm, Thomas Böttger, Y Sun, C W. Thiel, R L. Cone
Physics and Astronomy
We present the results of detailed site-selective spectroscopy performed on the I15∕24↔I13∕24 transition of Er3+:Y2SiO5 at 1.5μm. New determinations of the I13∕24 and I15∕24 crystal-field-level structure for the two crystallographically inequivalent Er3+ sites have been made. The fluorescence dynamics of the metastable I13∕24:Y1 excited state was investigated, showing exponential decays for Er3+ at both crystallographic sites with fluorescence lifetimes of 11.4ms for site 1 and 9.2ms for site 2. Exceptionally sharp inhomogeneous absorption lines of 180, 390, and 510MHz were observed in 0.0015% Er3+:Y2SiO5, 0.005% Er3+:Y2SiO5, and 0.02% Er3+:Y2SiO5 crystals, respectively. The g-values for the lowest energy I15∕24 (Z1) and …
A Cosmic Milestone: Constraints From Metal-Poor Halo Stars On The Cosmological Reionization Epoch, Aparna Venkatesan
A Cosmic Milestone: Constraints From Metal-Poor Halo Stars On The Cosmological Reionization Epoch, Aparna Venkatesan
Physics and Astronomy
Theoretical studies and current observations of the high-redshift intergalactic medium (IGM) indicate that at least two cosmic transitions occur by the time the universe reaches gas metallicities of about 10-3 Z☉. One is the cosmological reionization of the IGM, and the second is the transition from a primordial to present-day mode of star formation. We quantify this relation through new calculations of the ionizing radiation produced in association with the elements carbon, oxygen, and silicon observed in Galactic metal-poor halo stars, which are likely second-generation objects formed in the wake of primordial supernovae. We demonstrate that sufficient …
The Radiative Transport Of Dust In Primordial Galaxies And Second-Generation Star Formation, Aparna Venkatesan, Biman B. Nath, J Shull
The Radiative Transport Of Dust In Primordial Galaxies And Second-Generation Star Formation, Aparna Venkatesan, Biman B. Nath, J Shull
Physics and Astronomy
We investigate the radiativetransport of dust inprimordial galaxies in thepresence of the UVradiation field from thefirst metal-free stars. Wefind that dust createdin the first supernova(SN) explosions can bedriven through the interiorof the SN remnantto accumulate in theSN shells, where second-generationstars may form fromcompressed cooling gas. Thisscenario requires metal-free starsto form continuously overtimescales of up to10 Myr, consistent withrecent estimates. Silicate andgraphite grains, as wellas iron-bearing magnetites, aretransported to the shellsfor reasonable parameter assumptions,but their relative yieldsfrom primordial SNe isan important factor inthe resulting abundance ratios.We compare the resultsof segregated grain transportwith the current nucleosyntheticdata on extremely metal-poorGalactic halo stars. Fossilsignatures …
Effective Field Theory Program For Conformal Quantum Anomalies, Horacio E. Camblong
Effective Field Theory Program For Conformal Quantum Anomalies, Horacio E. Camblong
Physics and Astronomy
The emergence of conformal states is established for any problem involving a domain of scales where the long-range SO(2,1) conformally invariant interaction is applicable. Whenever a clear-cut separation of ultraviolet and infrared cutoffs is in place, this renormalization mechanism is capable of producing binding in the strong-coupling regime. A realization of this phenomenon, in the form of dipole-bound anions, is discussed.
Semiclassical Methods In Curved Spacetime And Black Hole Thermodynamics, Horacio E. Camblong
Semiclassical Methods In Curved Spacetime And Black Hole Thermodynamics, Horacio E. Camblong
Physics and Astronomy
Improved semiclassical techniques are developed and applied to a treatment of a real scalar field in a D-dimensional gravitational background. This analysis, leading to a derivation of the thermodynamics of black holes, is based on the simultaneous use of (i) a near-horizon description of the scalar field in terms of conformal quantum mechanics; (ii) a novel generalized WKB framework; and (iii) curved-spacetime phase-space methods. In addition, this improved semiclassical approach is shown to be asymptotically exact in the presence of hierarchical expansions of a near-horizon type. Most importantly, this analysis further supports the claim that the thermodynamics of black holes …
Black Hole Thermodynamics From Near-Horizon Conformal Quantum Mechanics, Horacio E. Camblong
Black Hole Thermodynamics From Near-Horizon Conformal Quantum Mechanics, Horacio E. Camblong
Physics and Astronomy
The thermodynamics of black holes is shown to be directly induced by their near-horizon conformal invariance. This behavior is exhibited using a scalar field as a probe of the black hole gravitational background, for a general class of metrics in D spacetime dimensions (with D≥4). The ensuing analysis is based on conformal quantum mechanics, within a hierarchical near-horizon expansion. In particular, the leading conformal behavior provides the correct quantum statistical properties for the Bekenstein-Hawking entropy, with the near-horizon physics governing the thermodynamics from the outset. Most importantly: (i) this treatment reveals the emergence of holographic properties; (ii) the conformal coupling …
Measuring Shared Information And Coordinated Activity In Neuronal Networks, K L. Klinkner, C R. Shalizi, Marcelo Camperi
Measuring Shared Information And Coordinated Activity In Neuronal Networks, K L. Klinkner, C R. Shalizi, Marcelo Camperi
Physics and Astronomy
Most nervous systems encode information about stimuli in the respond- ing activity of large neuronal networks. This activity often manifests itself as dynamically coordinated sequences of action potentials. Since multiple electrode recordings are now a standard tool in neuroscience research, it is important to have a measure of such network-wide behav- ioral coordination and information sharing, applicable to multiple neural spike train data. We propose a new statistic, informational coherence , which measures how much better one unit can be predicted by knowing the dynamical state of another. We argue informational coherence is a measure of association and shared information …
Thermoelectricity In Natural And Synthetic Hydrogels, Brandon R. Brown
Thermoelectricity In Natural And Synthetic Hydrogels, Brandon R. Brown
Physics and Astronomy
We describe a technique for measuring a Seebeck effect in gels and present data for three systems. notably distinct signals are obtained for gel originating in the electrosensitive organs of marine sharks, syntehtic collagen-based gel, and as a control, seawater, the gels' seawater simply confirms that gels suppress mass transport. The difference between synthetic gel and the gel of sharks shows that the charged polymers of the shark gel restrict mass transport much more successfully than the polumers of the collagen gel, and we submit that this sort of ion localization is key to the emergence of thermoelectricity in a …
Nucleosynthesis, Reionization, And The Mass Function Of The First Stars, Jason Tumlinson, Aparna Venkatesan, J Shull
Nucleosynthesis, Reionization, And The Mass Function Of The First Stars, Jason Tumlinson, Aparna Venkatesan, J Shull
Physics and Astronomy
We critique the hypothesisthat the first starswere very massive stars(VMSs; M > 140 M).We review the twomajor lines of evidencefor the existence ofVMSs: (1) that therelative metal abundances ofextremely metal-poor Galactic halostars show evidence ofVMS enrichment and (2)that the high electron-scatteringoptical depth (e) tothe cosmic microwave backgroundfound by the Wilkinson Microwave Anisotropy Probe(WMAP) requires VMSs forreionization in a concordanceCDM cosmology. The yieldpatterns of VMSs explodingas pair-instability supernovae areincompatible with the Fe-peakand r-process abundances inhalo stars. Models includingType II supernovae and/or"hypernovae" from zero-metallicity progenitorswith M = 840 Mcan better explain theobserved trends. We usethe …
Anomaly In Conformal Quantum Mechanics: From Molecular Physics To Black Holes, Horacio E. Camblong
Anomaly In Conformal Quantum Mechanics: From Molecular Physics To Black Holes, Horacio E. Camblong
Physics and Astronomy
A number of physical systems exhibit a particular form of asymptotic conformal invariance: within a particular domain of distances, they are characterized by a long-range conformal interaction (inverse square potential), the apparent absence of dimensional scales, and an SO(2,1) symmetry algebra. Examples from molecular physics to black holes are provided and discussed within a unified treatment. When such systems are physically realized in the appropriate strong-coupling regime, the occurrence of quantum symmetry breaking is possible. This anomaly is revealed by the failure of the symmetry generators to close the algebra in a manner shown to be independent of the renormalization …
So(2,1) Conformal Anomaly: Beyond Contact Interactions, Horacio E. Camblong
So(2,1) Conformal Anomaly: Beyond Contact Interactions, Horacio E. Camblong
Physics and Astronomy
The existence of anomalous symmetry-breaking solutions of the SO(2,1) commutator algebra is explicitly extended beyond the case of scale-invariant contact interactions. In particular, the failure of the conservation laws of the dilation and special conformal charges is displayed for the two-dimensional inverse square potential. As a consequence, this anomaly appears to be a generic feature of conformal quantum mechanics and not merely an artifact of contact interactions. Moreover, a renormalization procedure traces the emergence of this conformal anomaly to the ultraviolet sector of the theory, within which lies the apparent singularity.
Anomalous Commutator Algebra For Conformal Quantum Mechanics, Horacio E. Camblong
Anomalous Commutator Algebra For Conformal Quantum Mechanics, Horacio E. Camblong
Physics and Astronomy
The structure of the commutator algebra for conformal quantum mechanics is considered. Specifically, it is shown that the emergence of a dimensional scale by renormalization implies the existence of an anomaly or quantum-mechanical symmetry breaking, which is explicitly displayed at the level of the generators of the SO(2,1) conformal group. Correspondingly, the associated breakdown of the conservation of the dilation and special conformal charges is derived.
The Ionizing Efficiency Of The First Stars, Aparna Venkatesan, James W. Truran
The Ionizing Efficiency Of The First Stars, Aparna Venkatesan, James W. Truran
Physics and Astronomy
We investigate whether a single population of first stars could have influenced both the metal enrichment and reionization of the high-redshift intergalactic medium (IGM), by calculating the generated ionizing radiation per unit metal yield as a function of the metallicity of stellar populations. We examine the relation between the ionizing radiation and carbon created by the first stars, since the evidence for the widespread enrichment of the IGM at redshifts z about 3-4 comes from the detection of C IV absorption. We find that the number of ionizing photons per baryon generated in association with the detected IGM metallicity may …
Feedback From The First Supernovae In Protogalaxies: The Fate Of The Generated Metals, Keiichi Wada, Aparna Venkatesan
Feedback From The First Supernovae In Protogalaxies: The Fate Of The Generated Metals, Keiichi Wada, Aparna Venkatesan
Physics and Astronomy
We investigate the chemo-dynamical effects of multiple supernova explosions in the central region of primordial galaxies using three-dimensional hydrodynamical simulations of the inhomogenous interstellar medium down to parsec-scales. We find that the final protogalactic structure and metal distribution depend strongly on the number of SNe. Specifically, 1) 1000 SNe after an instantaneous burst of star formation are sufficient to almost completely blow away the gas in these systems, whereas 2) 100 SN explosions trigger the collapse of the protogalactic cloud, leading to the formation of a cold, dense clumpy disk (n > 300 cm^-3) with metallicity, Z = 4 10^-4 Z_sun. …
Cosmological Effects Of The First Stars: Evolving Spectra Of Population Iii, Jason Tumlinson, J Shull, Aparna Venkatesan
Cosmological Effects Of The First Stars: Evolving Spectra Of Population Iii, Jason Tumlinson, J Shull, Aparna Venkatesan
Physics and Astronomy
The first stars hold intrinsic interest for their uniqueness and for their potentially important contributions to galaxy formation, chemical enrichment, and feedback on the intergalactic medium (IGM). Although the sources of cosmological reionization are unknown at present, the declining population of large bright quasars at redshifts z > 3 implies that stars are the leading candidates for the sources that reionized the hydrogen in the IGM by z ~ 6. The metal-free composition of the first stars restricts the stellar energy source to proton-proton burning rather than the more efficient CNO cycle. Consequently, they are hotter, smaller, and have harder spectra …
Evolving Spectra Of Population Iii Stars: Consequences For Cosmological Reionization, Aparna Venkatesan, Jason Tumlinson, J Shull
Evolving Spectra Of Population Iii Stars: Consequences For Cosmological Reionization, Aparna Venkatesan, Jason Tumlinson, J Shull
Physics and Astronomy
We examine the significance of the first metal-free stars (Population III) for the cosmological reionization of H I and He II. These stars have unusually hard spectra, with the integrated ionizing photon rates from a Population III stellar cluster for H I and He II being 1.6 and 105 times stronger, respectively, than those from a Population II cluster. For the currently favored cosmology, we find that Population III stars alone can reionize H I at redshifts of z 9 and 4.7 and He II at z 5.1 and 0.7 for continuous and instantaneous modes of star formation, respectively. …
Material Optimization Of Er3+Y2sio5 At 1.5 Μm For Optical Processing, Memory, And Laser Frequency Stabilization Applications, Thomas Böttger, Y Sun, C W. Thiel, R L. Cone
Material Optimization Of Er3+Y2sio5 At 1.5 Μm For Optical Processing, Memory, And Laser Frequency Stabilization Applications, Thomas Böttger, Y Sun, C W. Thiel, R L. Cone
Physics and Astronomy
Spatial-spectral holography using spectral hole burning materials is a powerful technique for performing real-time, wide-bandwidth information storage and signal processing. For operation in the important 1.5 μm communication band, the material Er3+:Y2SiO5 enables applications such as laser frequency stabilization, all-optical correlators, analog signal processing, and data storage. Site-selective absorption and emission spectroscopy identified spectral hole burning transitions and excited state T1 lifetimes in the 1.5 μm spectral region. The effects of crystal temperature, Er3+-dopant concentration, magnetic field strength, and crystal orientation on spectral diffusion were explored using stimulated photon echo spectroscopy, which is the “prototype” interaction mechanism for device applications. …
Electrical Characterization Of Gel Collected From Shark Electrosensors, Brandon R. Brown
Electrical Characterization Of Gel Collected From Shark Electrosensors, Brandon R. Brown
Physics and Astronomy
To investigate the physical mechanism of the electric sense, we present an intial electrical characterization of the glycoprotein gel that fills the electrosensitive organs of marine elasmobranchs (sharks, skates, and rays). We have collected samples of this gel, postmortem, from three shark species, and removed the majority of dissolved salts in one sample via dialysis. Here we present the results of dc conductivity measurements, low-frequency impedance spectroscopy, and electrophoresis. Electrophoresis shows a range of large protein-based molecules fitting the expectations of glycoproteins, but the gels of different species exhibit litttle similarity. The electrophoresis signature is unaffected by thermal cycling and …
Renormalized Path Integral For The Two-Dimensional Δ-Function Interaction, Horacio E. Camblong
Renormalized Path Integral For The Two-Dimensional Δ-Function Interaction, Horacio E. Camblong
Physics and Astronomy
A path-integral approach for δ-function potentials is presented. Particular attention is paid to the two-dimensional case, which illustrates the realization of a quantum anomaly for a scale-invariant problem in quantum mechanics. Our treatment is based on an infinite summation of perturbation theory that captures the nonperturbative nature of the δ-function bound state. The well-known singular character of the two-dimensional δ-function potential is dealt with by considering the renormalized path integral resulting from a variety of schemes: dimensional, momentum-cutoff, and real-space regularization. Moreover, compatibility of the bound-state and scattering sectors is shown.
Coherent Integration Of 0.5 Ghz Spectral Holograms At 1536 Nm Using Dynamic Biphase Codes, Z Cole, Thomas Böttger, R Krishna Mohan, R Reibel, W R. Babbitt, R L. Cone, K D. Merkel
Coherent Integration Of 0.5 Ghz Spectral Holograms At 1536 Nm Using Dynamic Biphase Codes, Z Cole, Thomas Böttger, R Krishna Mohan, R Reibel, W R. Babbitt, R L. Cone, K D. Merkel
Physics and Astronomy
Spectral hole-burning-based optical processing devices are proposed for coherent integration of multiple high-bandwidth interference patterns in a spectral hole-burning medium. In this implementation, 0.5 GHz spectral holographic gratings are dynamically accumulated in Er3+:Y2SiO5" style="position: relative;" tabindex="0" id="MathJax-Element-1-Frame">Er3+:Y2SiO5 at 4.2 K using a 1536 nm laser frequency stabilized to a spectral hole, along with commercial off-the-shelf components. The processed data, representing time delays over 0.5–2.0 μs, were optically read out using a frequency-swept probe; this approach makes possible the use of low-bandwidth, large-dynamic-range detectors and digitizers and enables competitive processing for applications such as radar,lidar, and radio astronomy. Coherent integration …
Mutual Constraints Between Reionization Models And Parameter Extraction From Cosmic Microwave Background Data, Aparna Venkatesan
Mutual Constraints Between Reionization Models And Parameter Extraction From Cosmic Microwave Background Data, Aparna Venkatesan
Physics and Astronomy
Spectroscopic studies of high-redshift objects and increasingly precise data on the cosmic microwave background (CMB) are beginning to independently place strong complementary bounds on the epoch of hydrogen reionization. Parameter estimation from current CMB data continues, however, to be subject to several degeneracies. Here, we focus on those degeneracies in CMB parameter forecasts related to the optical depth to reionization. We extend earlier work on the mutual constraints that such analyses of CMB data and a reionization model may place on each other to a more general parameter set and to the case of data anticipated from the MAP satellite. …