Faculty Publications: February, 2016
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Title: | Thermodynamic properties of a quantum Hall anti-dot interferometer | |
Authors: | Levy Schreier, Sarah; Stern, Ady; Rosenow, Bernd; Halperin, Bertrand I. | |
Publication: | Physica E: Low-dimensional Systems and Nanostructures, Volume 76, p. 82-87. | |
Publication Date: | 02/2016 | |
Origin: | ELSEVIER | |
Keywords: | Quantum Hall effect | |
Abstract Copyright: | (c) 2016 Elsevier B.V. | |
DOI: | 10.1016/j.physe.2015.10.001 | |
Bibliographic Code: | 2016PhyE...76...82L |
Abstract
We study quantum Hall interferometers in which the interference loop encircles a quantum anti-dot. We base our study on thermodynamic considerations, which we believe reflect the essential aspects of interference transport phenomena. We find that similar to the more conventional Fabry-Perot quantum Hall interferometers, in which the interference loop forms a quantum dot, the anti-dot interferometer is affected by the electro-static Coulomb interaction between the edge modes defining the loop. We show that in the Aharonov-Bohm regime, in which effects of fractional statistics should be visible, is easier to access in interferometers based on anti-dots than in those based on dots. We discuss the relevance of our results to recent measurements on anti-dots interferometers.
Title: | Measurements of four-lepton production in pp collisions at √{ s} = 8 TeV with the ATLAS detector | |
Authors: | Aad, G.; Abbott, B.; Abdallah, J.; Abdinov, O.;... Franklin, M.;... Huth, J.;... Morii, M.;... and 2857 coauthors | |
Publication: | Physics Letters B, Volume 753, p. 552-572. | |
Publication Date: | 02/2016 | |
Origin: | ELSEVIER | |
Abstract Copyright: | (c) 2016 CERN for the benefit of the ATLAS Collaboration | |
DOI: | 10.1016/j.physletb.2015.12.048 | |
Bibliographic Code: | 2016PhLB..753..552A |
Abstract
The four-lepton (4ℓ, ℓ = e , μ) production cross section is measured in the mass range from 80 to 1000 GeV using 20.3 fb-1 of data in pp collisions at √{ s} = 8 TeV collected with the ATLAS detector at the LHC. The 4ℓ events are produced in the decays of resonant Z and Higgs bosons and the non-resonant ZZ continuum originating from q q bar , gg, and qg initial states. A total of 476 signal candidate events are observed with a background expectation of 26.2 ± 3.6 events, enabling the measurement of the integrated cross section and the differential cross section as a function of the invariant mass and transverse momentum of the four-lepton system.In the mass range above 180 GeV, assuming the theoretical constraint on the q q bar production cross section calculated with perturbative NNLO QCD and NLO electroweak corrections, the signal strength of the gluon-fusion component relative to its leading-order prediction is determined to be μgg = 2.4 ± 1.0 (stat.) ± 0.5 (syst.) ± 0.8 (theory).
Title: | Constraints on non-Standard Model Higgs boson interactions in an effective Lagrangian using differential cross sections measured in the H → γγ decay channel at √{ s} = 8 TeV with the ATLAS detector | |
Authors: | Aad, G.; Abbott, B.; Abdallah, J.; Abdinov, O.;... Franklin, M.;... Huth, J.;... Morii, M.;... and 2858 coauthors | |
Publication: | Physics Letters B, Volume 753, p. 69-85. | |
Publication Date: | 02/2016 | |
Origin: | ELSEVIER | |
Abstract Copyright: | (c) 2016 CERN for the benefit of the ATLAS Collaboration. | |
DOI: | 10.1016/j.physletb.2015.11.071 | |
Bibliographic Code: | 2016PhLB..753...69A |
Abstract
The strength and tensor structure of the Higgs boson's interactions are investigated using an effective Lagrangian, which introduces additional CP-even and CP-odd interactions that lead to changes in the kinematic properties of the Higgs boson and associated jet spectra with respect to the Standard Model. The parameters of the effective Lagrangian are probed using a fit to five differential cross sections previously measured by the ATLAS experiment in the H → γγ decay channel with an integrated luminosity of 20.3 fb-1 at √{ s} = 8 TeV. In order to perform a simultaneous fit to the five distributions, the statistical correlations between them are determined by re-analysing the H → γγ candidate events in the proton-proton collision data. No significant deviations from the Standard Model predictions are observed and limits on the effective Lagrangian parameters are derived. The statistical correlations are made publicly available to allow for future analysis of theories with non-Standard Model interactions.
Title: | The flagellar motor of Caulobacter crescentus generates more torque when a cell swims backwards | |
Authors: | Lele, Pushkar P.; Roland, Thibault; Shrivastava, Abhishek; Chen, Yihao; Berg, Howard C. | |
Publication: | Nature Physics, Volume 12, Issue 2, pp. 175-178 (2016). | |
Publication Date: | 02/2016 | |
Origin: | NATURE | |
Abstract Copyright: | (c) 2016: Nature Publishing Group | |
DOI: | 10.1038/nphys3528 | |
Bibliographic Code: | 2016NatPh..12..175L |
Abstract
The bacterium Caulobacter crescentus swims by rotating a single right-handed helical filament. These cells have two swimming modes: a pusher mode, in which clockwise (CW) rotation of the filament thrusts the cell body forwards, and a puller mode, in which counterclockwise (CCW) rotation pulls it backwards. The situation is reversed in Escherichia coli, a bacterium that rotates several left-handed filaments CCW to drive the cell body forwards. The flagellar motor in E. coli generates more torque in the CCW direction than the CW direction in swimming cells. However, C. crescentus and other bacteria with single filaments swim forwards and backwards at similar speeds, prompting the assumption that motor torques in the two modes are the same. Here, we present evidence that motors in C. crescentus develop higher torques in the puller mode than in the pusher mode, and suggest that the anisotropy in torque generation is similar in the two species, despite the differences in filament handedness and motor bias.
Title: | Atomic-scale electronic structure of the cuprate d-symmetry form factor density wave state | |
Authors: | Hamidian, M. H.; Edkins, S. D.; Kim, Chung Koo; Davis, J. C.; MacKenzie, A. P.; Eisaki, H.; Uchida, S.; Lawler, M. J.; Kim, E.-A.; Sachdev, S.; Fujita, K. | |
Publication: | Nature Physics, Volume 12, Issue 2, pp. 150-156 (2016). | |
Publication Date: | 02/2016 | |
Origin: | NATURE | |
Abstract Copyright: | (c) 2016: Nature Publishing Group | |
DOI: | 10.1038/nphys3519 | |
Bibliographic Code: | 2016NatPh..12..150H |
Abstract
Research on high-temperature superconducting cuprates is at present focused on identifying the relationship between the classic `pseudogap’ phenomenon and the more recently investigated density wave state. This state is generally characterized by a wavevector Q parallel to the planar Cu-O-Cu bonds along with a predominantly d-symmetry form factor (dFF-DW). To identify the microscopic mechanism giving rise to this state, one must identify the momentum-space states contributing to the dFF-DW spectral weight, determine their particle-hole phase relationship about the Fermi energy, establish whether they exhibit a characteristic energy gap, and understand the evolution of all these phenomena throughout the phase diagram. Here we use energy-resolved sublattice visualization of electronic structure and reveal that the characteristic energy of the dFF-DW modulations is actually the `pseudogap’ energy Δ1. Moreover, we demonstrate that the dFF-DW modulations at E = -Δ1 (filled states) occur with relative phase π compared to those at E = Δ1 (empty states). Finally, we show that the conventionally defined dFF-DW Q corresponds to scattering between the `hot frontier’ regions of momentum-space beyond which Bogoliubov quasiparticles cease to exist. These data indicate that the cuprate dFF-DW state involves particle-hole interactions focused at the pseudogap energy scale and between the four pairs of `hot frontier’ regions in momentum space where the pseudogap opens.
Title: | Spatially resolved edge currents and guided-wave electronic states in graphene | |
Authors: | Allen, M. T.; Shtanko, O.; Fulga, I. C.; Akhmerov, A. R.; Watanabe, K.; Taniguchi, T.; Jarillo-Herrero, P.; Levitov, L. S.; Yacoby, A. | |
Publication: | Nature Physics, Volume 12, Issue 2, pp. 128-133 (2016). | |
Publication Date: | 02/2016 | |
Origin: | NATURE | |
Abstract Copyright: | (c) 2016: Nature Publishing Group | |
DOI: | 10.1038/nphys3534 | |
Bibliographic Code: | 2016NatPh..12..128A |
Abstract
Exploiting the light-like properties of carriers in graphene could allow extreme non-classical forms of electronic transport to be realized. In this vein, finding ways to confine and direct electronic waves through nanoscale streams and streamlets, unimpeded by the presence of other carriers, has remained a grand challenge. Inspired by guiding of light in fibre optics, here we demonstrate a route to engineer such a flow of electrons using a technique for mapping currents at submicron scales. We employ real-space imaging of current flow in graphene to provide direct evidence of the confinement of electron waves at the edges of a graphene crystal near charge neutrality. This is achieved by using superconducting interferometry in a graphene Josephson junction and reconstructing the spatial structure of conducting pathways using Fourier methods. The observed edge currents arise from coherent guided-wave states, confined to the edge by band bending and transmitted as plane waves. As an electronic analogue of photon guiding in optical fibres, the observed states afford non-classical means for information transduction and processing at the nanoscale.
Title: | Measurement of the forward-backward asymmetry of top-quark and antiquark pairs using the full CDF Run II data set | |
Authors: | CDF Collaboration; Aaltonen, T.; Amerio, S.; Amidei, D.;... Franklin, M.;... and 391 coauthors | |
Publication: | eprint arXiv:1602.09015 | |
Publication Date: | 02/2016 | |
Origin: | ARXIV | |
Keywords: | High Energy Physics - Experiment | |
Comment: | To be submitted to Phys. Rev. D | |
Bibliographic Code: | 2016arXiv160209015C |
Abstract
We measure the forward--backward asymmetry of the production of top quark and antiquark pairs in proton-antiproton collisions at center-of-mass energy $\sqrt{s} = 1.96~\mathrm{TeV}$ using the full data set collected by the Collider Detector at Fermilab (CDF) in Tevatron Run II corresponding to an integrated luminosity of $9.1~\rm{fb}^{-1}$. The asymmetry is characterized by the rapidity difference between top quarks and antiquarks ($\Delta y$), and measured in the final state with two charged leptons (electrons and muons). The inclusive asymmetry, corrected to the entire phase space at parton level, is measured to be $A_{\text{FB}}^{t\bar{t}} = 0.12 \pm 0.13$, consistent with the expectations from the standard-model (SM) and previous CDF results in the final state with a single charged lepton. The combination of the CDF measurements of the inclusive $A_{\text{FB}}^{t\bar{t}}$ in both final states yields $A_{\text{FB}}^{t\bar{t}}=0.160\pm0.045$, which is consistent with the SM predictions. We also measure the differential asymmetry as a function of $\Delta y$. A linear fit to $A_{\text{FB}}^{t\bar{t}}(|\Delta y|)$, assuming zero asymmetry at $\Delta y=0$, yields a slope of $\alpha=0.14\pm0.15$, consistent with the SM prediction and the previous CDF determination in the final state with a single charged lepton. The combined slope of $A_{\text{FB}}^{t\bar{t}}(|\Delta y|)$ in the two final states is $\alpha=0.227\pm0.057$, which is $2.0\sigma$ larger than the SM prediction.
Title: | Localization and broadband follow-up of the gravitational-wave transient GW150914 | |
Authors: | Abbott, B. P.; Abbott, R.; Abbott, T. D.;... Stubbs, C. W.;... | |
Publication: | eprint arXiv:1602.08492 | |
Publication Date: | 02/2016 | |
Origin: | ARXIV | |
Keywords: | Astrophysics - High Energy Astrophysical Phenomena, General Relativity and Quantum Cosmology | |
Comment: | Submitted to ApJL | |
Bibliographic Code: | 2016arXiv160208492A |
Abstract
A gravitational-wave transient was identified in data recorded by the Advanced LIGO detectors on 2015 September 14. The event candidate, initially designated G184098 and later given the name GW150914, is described in detail elsewhere. By prior arrangement, preliminary estimates of the time, significance, and sky location of the event were shared with 63 teams of observers covering radio, optical, near-infrared, X-ray, and gamma-ray wavelengths with ground- and space-based facilities. In this Letter we describe the low-latency analysis of the gravitational wave data and present the sky localization of the first observed compact binary merger. We summarize the follow-up observations reported by 25 teams via private Gamma-ray Coordinates Network Circulars, giving an overview of the participating facilities, the gravitational wave sky localization coverage, the timeline and depth of the observations. As this event turned out to be a binary black hole merger, there is little expectation of a detectable electromagnetic signature. Nevertheless, this first broadband campaign to search for a counterpart of an Advanced LIGO source represents a milestone and highlights the broad capabilities of the transient astronomy community and the observing strategies that have been developed to pursue neutron star binary merger events. Detailed investigations of the electromagnetic data and results of the electromagnetic follow-up campaign will be disseminated in the papers of the individual teams.
Title: | Quantum metrology enhanced by repetitive quantum error correction | |
Authors: | Unden, Thomas; Balasubramanian, Priya; Louzon, Daniel; Vinkler, Yuval; Plenio, Martin B.; Markham, Matthew; Twitchen, Daniel; Lovchinsky, Igor; Sushkov, Alexander O.; Lukin, Mikhail D.; Retzker, Alex; Naydenov, Boris; McGuinness, Liam P.; Jelezko, Fedor | |
Publication: | eprint arXiv:1602.07144 | |
Publication Date: | 02/2016 | |
Origin: | ARXIV | |
Keywords: | Quantum Physics | |
Bibliographic Code: | 2016arXiv160207144U |
Abstract
The accumulation of quantum phase in response to a signal is the central mechanism of quantum sensing, as such, loss of phase information presents a fundamental limitation. For this reason approaches to extend quantum coherence in the presence of noise are actively being explored. Here we experimentally protect a room-temperature hybrid spin register against environmental decoherence by performing repeated quantum error correction whilst maintaining sensitivity to signal fields. We use a long-lived nuclear spin to correct multiple phase errors on a sensitive electron spin in diamond and realize magnetic field sensing beyond the timescales set by natural decoherence. The universal extension of sensing time, robust to noise at any frequency, demonstrates the definitive advantage entangled multi-qubit systems provide for quantum sensing and offers an important complement to quantum control techniques. In particular, our work opens the door for detecting minute signals in the presence of high frequency noise, where standard protocols reach their limits.
Title: | Confinement transition to density wave order in metallic doped spin liquids | |
Authors: | Patel, Aavishkar A.; Chowdhury, Debanjan; Allais, Andrea; Sachdev, Subir | |
Publication: | eprint arXiv:1602.05954 | |
Publication Date: | 02/2016 | |
Origin: | ARXIV | |
Keywords: | Condensed Matter - Strongly Correlated Electrons, Condensed Matter - Statistical Mechanics, High Energy Physics - Theory | |
Comment: | 30 pages, 8 figures | |
Bibliographic Code: | 2016arXiv160205954P |
Abstract
Insulating quantum spin liquids can undergo a confinement transition to a valence bond solid state via the condensation of topological excitations of the associated gauge theory. We extend the theory of such transitions to fractionalized Fermi liquids (FL*): these are metallic doped spin liquids in which the Fermi surfaces only have gauge neutral quasiparticles. Using insights from a duality transform on a doped quantum dimer model for the U(1)-FL* state, we show that projective symmetry group of the theory of the topological excitations remains unmodified, but the Fermi surfaces can lead to additional frustrating interactions. We propose a theory for the confinement transition of $\mathbb{Z}_2$-FL* states via the condensation of visons. A variety of confining, incommensurate density wave states are possible, including some that are similar to the incommensurate $d$-form factor density wave order observed in several recent experiments on the cuprate superconductors.
Title: | Quantum Statistics and Spacetime Surgery | |
Authors: | Wang, Juven; Wen, Xiao-Gang; Yau, Shing-Tung | |
Publication: | eprint arXiv:1602.05951 | |
Publication Date: | 02/2016 | |
Origin: | ARXIV | |
Keywords: | Condensed Matter - Strongly Correlated Electrons | |
Comment: | 4 pages + appendices. Special gratitude to Clifford H. Taubes. See also http://dspace.mit.edu/handle/1721.1/99285 and arXiv:1602.05569 | |
Bibliographic Code: | 2016arXiv160205951W |
Abstract
We apply the geometric-topology surgery theory on the spacetime manifold to study the constraints of quantum statistics data in 2+1 and 3+1 spacetime dimensions. First we introduce the fusion data for worldline and worldsheet operators capable creating anyon excitations of particles and strings, well-defined in gapped states of matter with intrinsic topological orders. Second we introduce the braiding statistics data of particles and strings, such as the geometric Berry matrices for particle-string Aharonov-Bohm and multi-loop adiabatic braiding process, encoded by submanifold linkings, in the closed spacetime 3-manifolds and 4-manifolds. Third we derive new "quantum surgery" constraints analogous to Verlinde formula associating fusion and braiding statistics data via spacetime surgery, essential for defining the theory of topological orders, and potentially correlated to bootstrap boundary physics such as gapless modes, conformal field theories or quantum anomalies.
Title: | The Information Capacity of Specific Interactions | |
Authors: | Huntley, Miriam H.; Murugan, Arvind; Brenner, Michael P. | |
Publication: | eprint arXiv:1602.05649 | |
Publication Date: | 02/2016 | |
Origin: | ARXIV | |
Keywords: | Condensed Matter - Soft Condensed Matter, Physics - Biological Physics, Quantitative Biology - Molecular Networks | |
Comment: | 7 pages, 5 figures | |
Bibliographic Code: | 2016arXiv160205649H |
Abstract
Specific interactions are a hallmark feature of self-assembly and signal-processing systems in both synthetic and biological settings. Specificity between components may arise from a wide variety of physical and chemical mechanisms in diverse contexts, from DNA hybridization to shape-sensitive depletion interactions. Despite this diversity, all systems that rely on interaction specificity operate under the constraint that increasing the number of distinct components inevitably increases off-target binding. Here we introduce `capacity', the maximal information encodable using specific interactions, to compare specificity across diverse experimental systems, and to compute how specificity changes with physical parameters. Using this framework, we find that `shape'-coding of interactions has higher capacity than chemical (`color') coding because the strength of off-target binding is strongly sublinear in binding site size for shapes while being linear for colors. We also find that different specificity mechanisms, such as shape and color, can be combined in a synergistic manner, giving a capacity greater than the sum of the parts.
Title: | Fivebranes and 3-manifold homology | |
Authors: | Gukov, Sergei; Putrov, Pavel; Vafa, Cumrun | |
Publication: | eprint arXiv:1602.05302 | |
Publication Date: | 02/2016 | |
Origin: | ARXIV | |
Keywords: | High Energy Physics - Theory, Mathematical Physics, Mathematics - Geometric Topology, Mathematics - Quantum Algebra | |
Comment: | 85 pages, 14 figures | |
Bibliographic Code: | 2016arXiv160205302G |
Abstract
Motivated by physical constructions of homological knot invariants, we study their analogs for closed 3-manifolds. We show that fivebrane compactifications provide a universal description of various old and new homological invariants of 3-manifolds. In terms of 3d/3d correspondence, such invariants are given by the Q-cohomology of the Hilbert space of partially topologically twisted 3d N=2 theory T[M_3] on a Riemann surface with defects. We demonstrate this by concrete and explicit calculations in the case of monopole/Heegaard Floer homology and a 3-manifold analog of Khovanov-Rozansky link homology. The latter gives a categorification of Chern-Simons partition function. Some of the new key elements include the explicit form of the S-transform and a novel connection between categorification and a previously mysterious role of Eichler integrals in Chern-Simons theory.
Title: | The Optical-Infrared Extinction Curve and its Variation in the Milky Way | |
Authors: | Schlafly, E. F.; Meisner, A. M.; Stutz, A. M.; Kainulainen, J.; Peek, J. E. G.; Tchernyshyov, K.; Rix, H.-W.; Finkbeiner, D. P.; Covey, K. R.; Green, G. M.; Bell, E. F.; Burgett, W. S.; Chambers, K. C.; Draper, P. W.; Flewelling, H.; Hodapp, K. W.; Kaiser, N.; Magnier, E. A.; Martin, N. F.; Metcalfe, N.; Wainscoat, R. J.; Waters, C. | |
Publication: | eprint arXiv:1602.03928 | |
Publication Date: | 02/2016 | |
Origin: | ARXIV | |
Keywords: | Astrophysics - Astrophysics of Galaxies, Astrophysics - Solar and Stellar Astrophysics | |
Comment: | 26 pages, 20 figures, comments welcome | |
Bibliographic Code: | 2016arXiv160203928S |
Abstract
The dust extinction curve is a critical component of many observational programs and an important diagnostic of the physics of the interstellar medium. Here we present new measurements of the dust extinction curve and its variation towards tens of thousands of stars, a hundred-fold larger sample than in existing detailed studies. We use data from the APOGEE spectroscopic survey in combination with ten-band photometry from Pan-STARRS1, 2MASS, and WISE. We find that the extinction curve in the optical through infrared is well characterized by a one-parameter family of curves described by R(V). The extinction curve is more uniform than suggested in past works, with sigma(R(V)) = 0.18, and with less than one percent of sight lines having R(V) > 4. Our data and analysis have revealed two new aspects of Galactic extinction: first, we find significant, wide-area variations in R(V) throughout the Galactic plane. These variations are on scales much larger than individual molecular clouds, indicating that R(V) variations must trace much more than just grain growth in dense molecular environments. Indeed, we find no correlation between R(V) and dust column density up to E(B-V) ~ 2. Second, we discover a strong relationship between R(V) and the far-infrared dust emissivity.
Title: | New N = 2 dualities | |
Authors: | Xie, Dan; Yau, Shing-Tung | |
Publication: | eprint arXiv:1602.03529 | |
Publication Date: | 02/2016 | |
Origin: | ARXIV | |
Keywords: | High Energy Physics - Theory | |
Comment: | 4 pages, 10 figures | |
Bibliographic Code: | 2016arXiv160203529X |
Abstract
We consider N = 2 superconformal field theory with following properties: a) Coulomb branch operators have fractional scaling dimensions, b) there are exact marginal deformations . The weakly coupled gauge theory descriptions are found by decomposing 3d mirror into different components, and different decompositions correspond to different duality frames. The gauge theory is formed by gauging Argyres-Douglas matter, and we write down all duality frames for several classes with infinite sequence of theories.
Title: | Receptor arrays optimized for natural odor statistics | |
Authors: | Zwicker, David; Murugan, Arvind; Brenner, Michael P. | |
Publication: | eprint arXiv:1602.02974 | |
Publication Date: | 02/2016 | |
Origin: | ARXIV | |
Keywords: | Physics - Biological Physics, Quantitative Biology - Neurons and Cognition | |
Comment: | 8 pages, 6 figures | |
Bibliographic Code: | 2016arXiv160202974Z |
Abstract
Natural odors typically consist of many molecules at different concentrations. It is unclear how the numerous odorant molecules and their possible mixtures are discriminated by relatively few olfactory receptors. Using an information-theoretic model, we show that a receptor array is optimal for this task if it achieves two possibly conflicting goals: (i) each receptor should respond to half of all odors and (ii) the response of different receptors should be uncorrelated when averaged over odors presented with natural statistics. We use these design principles to predict statistics of the affinities between receptors and odorant molecules for a broad class of odor statistics. We also show that optimal receptor arrays can be tuned to either resolve concentrations well or distinguish mixtures reliably. Finally, we use our results to predict properties of experimentally measured receptor arrays. Our work can thus be used to better understand natural olfaction and it also suggests ways to improve artificial sensor arrays.
Title: | Near-horizon Kerr Magnetosphere | |
Authors: | Gralla, Samuel E.; Lupsasca, Alexandru; Strominger, Andrew | |
Publication: | eprint arXiv:1602.01833 | |
Publication Date: | 02/2016 | |
Origin: | ARXIV | |
Keywords: | High Energy Physics - Theory, Astrophysics - High Energy Astrophysical Phenomena, General Relativity and Quantum Cosmology | |
Comment: | 8 pages, 2 figures | |
Bibliographic Code: | 2016arXiv160201833G |
Abstract
We exploit the near-horizon conformal symmetry of rapidly spinning black holes to determine universal properties of their magnetospheres. Analytic expressions are derived for the limiting form of the magnetosphere in the near-horizon region. The symmetry is shown to imply that the black hole Meissner effect holds for free Maxwell fields but is generically violated for force-free fields. We further show that in the extremal limit, near-horizon plasma particles are infinitely boosted relative to accretion flow. Active galactic nuclei powered by rapidly spinning black holes are therefore natural sites for high energy particle collisions.
Title: | A direct approach to quantum tunneling | |
Authors: | Andreassen, Anders; Farhi, David; Frost, William; Schwartz, Matthew D. | |
Publication: | eprint arXiv:1602.01102 | |
Publication Date: | 02/2016 | |
Origin: | ARXIV | |
Keywords: | High Energy Physics - Theory, High Energy Physics - Phenomenology | |
Comment: | 5 pages, 2 figures | |
Bibliographic Code: | 2016arXiv160201102A |
Abstract
The decay rates of quasistable states in quantum field theories are usually calculated using instanton methods. Standard derivations of these methods rely in a crucial way upon deformations and analytic continuations of the physical potential, and on the saddle point approximation. While the resulting procedure can be checked against other semi-classical approaches in some one-dimensional cases, it is challenging to trace the role of the relevant physical scales, and any intuitive handle on the precision of the approximations involved are at best obscure. In this paper, we use a physical definition of the tunneling probability to derive a formula for the decay rate in both quantum mechanics and quantum field theory directly from the Minkowski path integral, without reference to unphysical deformations of the potential. There are numerous benefits to this approach, from non-perturbative applications to precision calculations and aesthetic simplicity.
Title: | Optical magnetic detection of single-neuron action potentials using quantum defects in diamond | |
Authors: | Barry, J. F.; Turner, M. J.; Schloss, J. M.; Glenn, D. R.; Song, Y.; Lukin, M. D.; Park, H.; Walsworth, R. L. | |
Publication: | eprint arXiv:1602.01056 | |
Publication Date: | 02/2016 | |
Origin: | ARXIV | |
Keywords: | Quantum Physics, Condensed Matter - Mesoscale and Nanoscale Physics, Physics - Atomic Physics, Quantitative Biology - Neurons and Cognition | |
Comment: | 23 pages, 12 figures, 2 tables | |
Bibliographic Code: | 2016arXiv160201056B |
Abstract
A key challenge for neuroscience is noninvasive, label-free sensing of action potential (AP) dynamics in whole organisms with single-neuron resolution. Here, we present a new approach to this problem: using nitrogen-vacancy (NV) quantum defects in diamond to measure the time-dependent magnetic fields produced by single-neuron APs. Our technique has a unique combination of features: (i) it is noninvasive, as the light that probes the NV sensors stays within the biocompatible diamond chip and does not enter the organism, enabling activity monitoring over extended periods; (ii) it is label-free and should be widely applicable to most organisms; (iii) it provides high spatial and temporal resolution, allowing precise measurement of the AP waveforms and conduction velocities of individual neurons; (iv) it directly determines AP propagation direction through the inherent sensitivity of NVs to the associated AP magnetic field vector; (v) it is applicable to neurons located within optically opaque tissue or whole organisms, through which magnetic fields pass largely unperturbed; and (vi) it is easy-to-use, scalable, and can be integrated with existing techniques such as wide-field and superresolution imaging. We demonstrate our method using excised single neurons from two invertebrate species, marine worm and squid; and then by single-neuron AP magnetic sensing exterior to whole, live, opaque marine worms for extended periods with no adverse effect. The results lay the groundwork for real-time, noninvasive 3D magnetic mapping of functional neuronal networks, ultimately with synapse-scale (~10 nm) resolution and circuit-scale (~1 cm) field-of-view.
Title: | Measurement of the Multiple-Muon Charge Ratio in the MINOS Far Detector | |
Authors: | Minos Collaboration; Adamson, P.; Anghel, I.; Aurisano, A.;... Feldman, G. J.;... ; and 116 coauthors | |
Publication: | eprint arXiv:1602.00783 | |
Publication Date: | 02/2016 | |
Origin: | ARXIV | |
Keywords: | High Energy Physics - Experiment, Physics - Instrumentation and Detectors | |
Comment: | 10 pages, 2 figures | |
Bibliographic Code: | 2016arXiv160200783M |
Abstract
The charge ratio, $R_\mu = N_{\mu^+}/N_{\mu^-}$, for cosmogenic multiple-muon events observed at an under- ground depth of 2070 mwe has been measured using the magnetized MINOS Far Detector. The multiple-muon events, recorded nearly continuously from August 2003 until April 2012, comprise two independent data sets imaged with opposite magnetic field polarities, the comparison of which allows the systematic uncertainties of the measurement to be minimized. The multiple-muon charge ratio is determined to be $R_\mu = 1.104 \pm 0.006 {\rm \,(stat.)} ^{+0.009}_{-0.010} {\rm \,(syst.)} $. This measurement complements previous determinations of single-muon and multiple-muon charge ratios at underground sites and serves to constrain models of cosmic ray interactions at TeV energies.
Title: | Efficiency of Cathodoluminescence Emission by Nitrogen-Vacancy Color Centers in Nanodiamond | |
Authors: | Zhang, Huiliang; Glenn, David R.; Schalek, Richard; Lichtman, Jeff W.; Walsworth, Ronald L. | |
Publication: | eprint arXiv:1602.00410 | |
Publication Date: | 02/2016 | |
Origin: | ARXIV | |
Keywords: | Condensed Matter - Materials Science | |
Bibliographic Code: | 2016arXiv160200410Z |
Abstract
Correlated electron microscopy and cathodoluminescence (CL) imaging using functionalized nanoparticles is a promising nanoscale probe of biological structure and function. Nanodiamonds (NDs) that contain CL-emitting color centers are particularly well suited for such applications. The intensity of CL emission from NDs is determined by a combination of factors, including: particle size; density of color centers; efficiency of energy deposition by electrons passing through the particle; and conversion efficiency from deposited energy to CL emission. We report experiments and numerical simulations that investigate the relative importance of each of these factors in determining CL emission intensity from NDs containing nitrogen-vacancy (NV) color centers. In particular, we find that CL can be detected from NV-doped NDs with dimensions as small as ~ 40 nm, although CL emission decreases significantly for smaller NDs.
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