Faculty Publications: July, 2014

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Title:
Homotopy theory for digraphs
Authors:
Grigor'yan, Alexander; Lin, Yong; Muranov, Yuri; Yau, Shing-Tung
Publication:
eprint arXiv:1407.0234
Publication Date:
07/2014
Origin:
ARXIV
Keywords:
Mathematics - Algebraic Topology
Comment:
39 pages, 15 figures
Bibliographic Code:
2014arXiv1407.0234G

Abstract

We introduce a homotopy theory of digraphs (directed graphs) and prove its basic properties, including the relations to the homology theory of digraphs constructed by the authors in previous papers. In particular, we prove the homotopy invariance of homologies of digraphs and the relation between the fundamental group of the digraph and its first homology group. The category of (undirected) graphs can be identified by a natural way with a full subcategory of digraphs. Thus we obtain also consistent homology and homotopy theories for graphs. Note that the homotopy theory for graphs coincides with the one constructed in the paper of Babson et.

 

Title:
Intermediate band conduction in femtosecond-laser hyperdoped silicon
Authors:
Sher, Meng-Ju; Mazur, Eric
Publication:
Applied Physics Letters, Volume 105, Issue 3, id.032103 (ApPhL Homepage)
Publication Date:
07/2014
Origin:
AIP
Abstract Copyright:
2014: AIP Publishing LLC
DOI:
10.1063/1.4890618
Bibliographic Code:
2014ApPhL.105c2103S

Abstract

We use femtosecond-laser hyperdoping to introduce non-equilibrium concentrations of sulfur into silicon and study the nature of the resulting intermediate band. With increasing dopant concentration, the sub-bandgap absorption increases. To better understand the dopant energetics, we perform temperature-dependent Hall and resistivity measurements. We analyze the carrier concentration and the energetics of the intermediate band using a two-band model. The temperature-dependence of the carrier concentration and resistivity suggests that the dopant concentration is below the insulator-to-metal transition and that the samples have a localized intermediate band at 70 meV below the conduction band edge.

 

Title:
Electron reconstruction and identification efficiency measurements with the ATLAS detector using the 2011 LHC proton-proton collision data
Authors:
Aad, G.; Abajyan, T.; Abbott, B.;... ; Franklin, M.;... Guimarães da Costa, J.;... Huth, J.;...; Morii, M.; and 2885 coauthors
Publication:
The European Physical Journal C, Volume 74, article id. #2941 (EPJC Homepage)
Publication Date:
07/2014
Origin:
SPRINGER
Abstract Copyright:
(c) 2014: The Author(s)
DOI:
10.1140/epjc/s10052-014-2941-0
Bibliographic Code:
2014EPJC...74.2941A

Abstract

Many of the interesting physics processes to be measured at the LHC have a signature involving one or more isolated electrons. The electron reconstruction and identification efficiencies of the ATLAS detector at the LHC have been evaluated using proton-proton collision data collected in 2011 at TeV and corresponding to an integrated luminosity of 4.7 fb. Tag-and-probe methods using events with leptonic decays of and bosons and mesons are employed to benchmark these performance parameters. The combination of all measurements results in identification efficiencies determined with an accuracy at the few per mil level for electron transverse energy greater than 30 GeV.

 

Title:
Asymptotic symmetries of Yang-Mills theory
Authors:
Strominger, Andrew
Publication:
Journal of High Energy Physics, Volume 2014, article id. #151
Publication Date:
07/2014
Origin:
SPRINGER
Keywords:
Scattering Amplitudes, Gauge Symmetry, Classical Theories of Gravity
Abstract Copyright:
(c) 2014: The Author(s)
DOI:
10.1007/JHEP07(2014)151
Bibliographic Code:
2014JHEP...07..151S

Abstract

Asymptotic symmetries at future null infinity ( +) of Minkowski space for electrodynamics with massless charged fields, as well as nonabelian gauge theories with gauge group G, are considered at the semiclassical level. The possibility of charge/color flux through + suggests the symmetry group is infinite-dimensional. It is conjectured that the symmetries include a G Kac-Moody symmetry whose generators are "large" gauge transformations which approach locally holomorphic functions on the conformal two-sphere at + and are invariant under null translations. The Kac-Moody currents are constructed from the gauge field at the future boundary of +. The current Ward identities include Weinberg's soft photon theorem and its colored extension.

 

Title:
On BMS invariance of gravitational scattering
Authors:
Strominger, Andrew
Affiliation:
AA(Center for the Fundamental Laws of Nature, Harvard University)
Publication:
Journal of High Energy Physics, Volume 2014, article id. #152
Publication Date:
07/2014
Origin:
SPRINGER
Keywords:
Scattering Amplitudes, Classical Theories of Gravity, Space-Time Symmetries
Abstract Copyright:
(c) 2014: The Author(s)
DOI:
10.1007/JHEP07(2014)152
Bibliographic Code:
2014JHEP...07..152S

Abstract

BMS+ transformations act nontrivially on outgoing gravitational scattering data while preserving intrinsic structure at future null infinity ( +). BMS- transformations similarly act on ingoing data at past null infinity ( -). In this paper we apply — within a suitable finite neighborhood of the Minkowski vacuum — results of Christodoulou and Klainerman to link + to - and thereby identify "diagonal" elements BMS0 of BMS+ × BMS-. We argue that BMS0 is a nontrivial infinite-dimensional symmetry of both classical gravitational scattering and the quantum gravity -matrix. It implies the conservation of net accumulated energy flux at every angle on the conformal S 2 at . The associated Ward identity is shown to relate S-matrix elements with and without soft gravitons. Finally, BMS0 is recast as a U(1) Kac-Moody symmetry and an expression for the Kac-Moody current is given in terms of a certain soft graviton operator on the boundary of.

 

Title:
Measurement of χ c1 and χ c2 production with = 7 TeV pp collisions at ATLAS
Authors:
Aad, G.; Abajyan, T.; Abbott, B.;... ; Franklin, M.;... Guimarães da Costa, J.;... Huth, J.;...; Morii, M.; and 2925 coauthors
Publication:
Journal of High Energy Physics, Volume 2014, article id. #154
Publication Date:
07/2014
Origin:
SPRINGER
Keywords:
Hadron-Hadron Scattering
Abstract Copyright:
(c) 2014: The Author(s)
DOI:
10.1007/JHEP07(2014)154
Bibliographic Code:
2014JHEP...07..154A

Abstract

The prompt and non-prompt production cross-sections for the χ c1 and χ c2 charmonium states are measured in pp collisions at = 7 TeV with the ATLAS detector at the LHC using 4 .5 fb-1 of integrated luminosity. The χ c states are reconstructed through the radiative decay χ c → J/ψγ (with J/ψ → μ + μ -) where photons are reconstructed from γ → e + e - conversions. The production rate of the χ c2 state relative to the χ c1 state is measured for prompt and non-prompt χ c as a function of J/ψ transverse momentum. The prompt χ c cross-sections are combined with existing measurements of prompt J/ψ production to derive the fraction of prompt J/ψ produced in feed-down from χ c decays. The fractions of χ c1 and χ c2 produced in b-hadron decays are also measured. [Figure not available: see fulltext.]

 

Title:
Changes in the Morphology and Proliferation of Astrocytes Induced by Two Modalities of Chemically Functionalized Single-Walled Carbon Nanotubes are Differentially Mediated by Glial Fibrillary Acidic Protein
Authors:
Gottipati, Manoj K.; Bekyarova, Elena; Brenner, Michael; Haddon, Robert C.; Parpura, Vladimir
Publication:
Nano Letters, vol. 14, issue 7, pp. 3720-3727
Publication Date:
07/2014
Origin:
CROSSREF
DOI:
10.1021/nl4048114
Bibliographic Code:
2014NanoL..14.3720G

Abstract

Not Available

 

Title:
Theory of Structural Transformation in Lithiated Amorphous Silicon
Authors:
Cubuk, Ekin D.; Kaxiras, Efthimios
Publication:
Nano Letters, vol. 14, issue 7, pp. 4065-4070
Publication Date:
07/2014
Origin:
CROSSREF
DOI:
10.1021/nl5015525
Bibliographic Code:
2014NanoL..14.4065C

Abstract

Not Available

 

Title:
Spectral function of a localized fermion coupled to the Wilson-Fisher conformal field theory
Authors:
Allais, Andrea; Sachdev, Subir
Publication:
Physical Review B, Volume 90, Issue 3, id.035131 (PhRvB Homepage)
Publication Date:
07/2014
Origin:
APS
PACS Keywords:
Non-Fermi-liquid ground states electron phase diagrams and phase transitions in model systems
Abstract Copyright:
2014: American Physical Society
DOI:
10.1103/PhysRevB.90.035131
Bibliographic Code:
2014PhRvB..90c5131A

Abstract

We describe the dynamics of a single fermion in a dispersionless band coupled to the 2+1 dimensional conformal field theory (CFT) describing the quantum phase transition of a bosonic order parameter with N components. The fermionic spectral functions are expected to apply to the vicinity of quantum critical points in two-dimensional metals over an intermediate temperature regime where the Landau damping of the order parameter can be neglected. Some of our results are obtained by a mapping to an auxiliary problem of a CFT containing a defect line with an external field which locally breaks the global O(N) symmetry.

 

Title:
Observation of muon intensity variations by season with the MINOS near detector
Authors:
Adamson, P.; Anghel, I.; Aurisano, A.;... Feldman, G. J.;... and 109 coauthors (Minos Collaboration)
Publication:
Physical Review D, Volume 90, Issue 1, id.012010 (PhRvD Homepage)
Publication Date:
07/2014
Origin:
APS
PACS Keywords:
Neutrino muon pion and other elementary particle detectors, cosmic ray detectors, Cosmic-ray interactions, Cosmic rays
Abstract Copyright:
2014: American Physical Society
DOI:
10.1103/PhysRevD.90.012010
Bibliographic Code:
2014PhRvD..90a2010A

Abstract

A sample of 1.53×109 cosmic-ray-induced single muon events has been recorded at 225 m water equivalent using the MINOS near detector. The underground muon rate is observed to be highly correlated with the effective atmospheric temperature. The coefficient αT, relating the change in the muon rate to the change in the vertical effective temperature, is determined to be 0.428±0.003(stat.)±0.059(syst.). An alternative description is provided by the weighted effective temperature, introduced to account for the differences in the temperature profile and muon flux as a function of zenith angle. Using the latter estimation of temperature, the coefficient is determined to be 0.352±0.003(stat.)±0.046(syst.).

 

Title:
Search for new physics in trilepton events and limits on the associated chargino-neutralino production at CDF
Authors:
Aaltonen, T.; Amerio, S.; Amidei, D.;... Franklin, M.; Guimaraes da Costa, J.;... ; and 403 coauthors
Publication:
Physical Review D, Volume 90, Issue 1, id.012011 (PhRvD Homepage)
Publication Date:
07/2014
Origin:
APS
PACS Keywords:
Supersymmetric models, Inclusive production with identified leptons photons or other nonhadronic particles, Limits on production of particles, Supersymmetric partners of known particles
Abstract Copyright:
2014: American Physical Society
DOI:
10.1103/PhysRevD.90.012011
Bibliographic Code:
2014PhRvD..90a2011A

Abstract

We perform a search for new physics using final states consisting of three leptons and a large imbalance in transverse momentum resulting from proton-antiproton collisions at 1.96 TeV center-of-mass energy. We use data corresponding to 5.8 fb-1 of integrated luminosity recorded by the CDF II detector at the Tevatron collider. Our main objective is to investigate possible new low-momentum (down to 5 GeV/c) multileptonic final states not investigated by LHC experiments. Relative to previous CDF analyses, we expand the geometric and kinematic coverage of electrons and muons and utilize tau leptons that decay hadronically. Inclusion of tau leptons is particularly important for supersymmetry (SUSY) searches. The results are consistent with standard-model predictions within 1.85σ. By optimizing our event selection to increase sensitivity to the minimal supergravity (mSUGRA) SUSY model, we set limits on the associated production of chargino and next-to-lightest neutralino, the SUSY partners of the electroweak gauge bosons. We exclude cross sections up to 0.1 pb and chargino masses up to 168 GeV/c2 at 95% C.L., for a suitable set of mSUGRA parameters. We also exclude a region of the two-dimensional space of the masses of the neutralino and the supersymmetric partner of the tau lepton, not previously excluded at the Tevatron.

 

Title:
Study of orbitally excited B mesons and evidence for a new Bπ resonance
Authors:
Aaltonen, T.; Amerio, S.; Amidei, D.;... Franklin, M.; Guimaraes da Costa, J.;... ; and 405 coauthors
Publication:
Physical Review D, Volume 90, Issue 1, id.012013 (PhRvD Homepage)
Publication Date:
07/2014
Origin:
APS
PACS Keywords:
Bottom mesons, Hadron mass models and calculations, Decays of bottom mesons
Abstract Copyright:
2014: American Physical Society
DOI:
10.1103/PhysRevD.90.012013
Bibliographic Code:
2014PhRvD..90a2013A

Abstract

Using the full CDF Run II data sample, we report evidence for a new resonance, which we refer to as B(5970), found simultaneously in the B0π+ and B+π- mass distributions with a significance of 4.4 standard deviations. We further report the first study of resonances consistent with orbitally excited B+ mesons and an updated measurement of the properties of orbitally excited B0 and Bs0 mesons. We measure the masses and widths of all states, as well as the relative production rates of the B1, B2*, and B(5970) states and the branching fraction of the Bs2*0 state to either B*+K- and B+K-. Furthermore, we measure the production rates of the orbitally excited B0,+ states relative to the B0,+ ground state. The masses of the new B(5970) resonances are 5978±5(stat)±12(syst) MeV/c2 for the neutral state and 5961±5(stat)±12(syst) MeV /c2 for the charged state, assuming that the resonance decays into Bπ final states. The properties of the orbitally excited and the new B(59700,+) states are compatible with isospin symmetry.

 

Title:
Measurement of the Inclusive Leptonic Asymmetry in Top-Quark Pairs that Decay to Two Charged Leptons at CDF
Authors:
Aaltonen, T.; Amerio, S.; Amidei, D.;... Franklin, M.; Guimaraes da Costa, J.;... ; and 404 coauthors
Publication:
Physical Review Letters, Volume 113, Issue 4, id.042001 (PhRvL Homepage)
Publication Date:
07/2014
Origin:
APS
PACS Keywords:
Top quarks, Charge conjugation parity time reversal and other discrete symmetries, Experimental tests, Inclusive production with identified leptons photons or other nonhadronic particles
Abstract Copyright:
2014: American Physical Society
DOI:
10.1103/PhysRevLett.113.042001
Bibliographic Code:
2014PhRvL.113d2001A

Abstract

We measure the inclusive forward-backward asymmetry of the charged-lepton pseudorapidities from top-quark pairs produced in proton-antiproton collisions and decaying to final states that contain two charged leptons (electrons or muons). The data are collected with the Collider Detector at Fermilab and correspond to an integrated luminosity of 9.1 fb-1. We measure the leptonic forward-backward asymmetry,AFB, to be 0.072±0.060 and the leptonic pair forward-backward asymmetry, AFBℓℓ, to be 0.076±0.082. The measured values can be compared with the standard model predictions of AFB=0.038±0.003 and AFBℓℓ=0.048±0.004, respectively. Additionally, we combine the AFBresult with a previous determination from a final state with a single lepton and hadronic jets and obtain AFB=0.090-0.026+0.028.

 

Title:
The dynamics of sperm cooperation in a competitive environment
Authors:
Fisher, H. S.; Giomi, L.; Hoekstra, H. E.; Mahadevan, L.
Publication:
eprint arXiv:1407.0666
Publication Date:
07/2014
Origin:
ARXIV
Keywords:
Quantitative Biology - Cell Behavior, Condensed Matter - Soft Condensed Matter, Physics - Biological Physics
Comment:
21 pages, 7 figures
Bibliographic Code:
2014arXiv1407.0666F

Abstract

Sperm cooperation has evolved in a variety of taxa and is often considered a response to sperm competition, yet the benefit of this form of collective movement remains unclear. Here we use fine-scale imaging and a minimal mathematical model to study sperm aggregation in the rodent genus $Peromyscus$. We demonstrate that as the number of sperm cells in an aggregate increase, the group moves with more persistent linearity but without increasing speed; this benefit, however, is offset in larger aggregates as the geometry of the group forces sperm to swim against one another. The result is a non-monotonic relationship between aggregate size and average velocity with both a theoretically predicted and empirically observed optimum of 6-7 sperm/aggregate. To understand the role of sexual selection in driving these sperm group dynamics, we compared two sister-species with divergent mating systems and find that sperm of $P.\,maniculatus$ (highly promiscuous), which have evolved under intense competition, form optimal-sized aggregates more often than sperm of $P.\,polionotus$ (strictly monogamous), which lack competition. Our combined mathematical and experimental study of coordinated sperm movement reveals the importance of geometry, motion and group size on sperm velocity and suggests how these physical variables interact with evolutionary selective pressures to regulate cooperation in competitive environments.

 

Title:
Fluid driven fingering instability of a confined elastic meniscus
Authors:
Biggins, J. S.; Wei, Z.; Mahadevan, L.
Publication:
eprint arXiv:1407.0684
Publication Date:
07/2014
Origin:
ARXIV
Keywords:
Condensed Matter - Soft Condensed Matter, Condensed Matter - Materials Science, Physics - Fluid Dynamics
Bibliographic Code:
2014arXiv1407.0684B

Abstract

When a fluid is pumped into a cavity in a confined elastic layer, at a critical pressure, destabilizing fingers of fluid invade the elastic solid along its meniscus (Saintyves, Dauchot, and Bouchaud, 2013). These fingers occur without fracture or loss of adhesion and are reversible, disappearing when the pressure is decreased. We develop an asymptotic theory of pressurized highly elastic layers trapped between rigid bodies to explain these observations, with predictions for the critical fluid pressure for fingering, and the finger wavelength. We also show that the theory links this fluid-driven fingering with a similar transition driven instead by transverse stretching of the elastic layer. We further verify these predictions by using finite-element simulations on the two systems which show that, in both cases, the fingering transition is first-order (sudden) and hence has a region of bistability. Our predictions are in good agreement with recent observations of this elastic analog of the classical Saffman-Taylor interfacial instability in hydrodynamics.

 

Title:
2D and Axisymmetric Incompressible Elastic Green's Functions
Authors:
Biggins, J. S.; Wei, Z.; Mahadevan, L.
Publication:
eprint arXiv:1407.1405
Publication Date:
07/2014
Origin:
ARXIV
Keywords:
Condensed Matter - Soft Condensed Matter, Condensed Matter - Materials Science, Physics - Biological Physics, Physics - Fluid Dynamics
Bibliographic Code:
2014arXiv1407.1405B

Abstract

We compile a list of 2-D and axisymmetric Green's functions for isotropic full and half spaces, to complement our letter "Linear elasticity of incompressible solids". We also extend the isotropic exactly incompressible linear theory from our letter to include isotropic neo-Hookean solids subject to a large pre-strain, and present Green's functions in these cases. The Green's function for a pre-strained half-space reproduces the Biot instability.

 

Title:
Singularities and Gauge Theory Phases II
Authors:
Esole, Mboyo; Shao, Shu-Heng; Yau, Shing-Tung
Publication:
eprint arXiv:1407.1867
Publication Date:
07/2014
Origin:
ARXIV
Keywords:
High Energy Physics - Theory, Mathematics - Algebraic Geometry
Comment:
v2: 48 pages, 20 figures; typos corrected, refs added, 1 figure added, note added at the end of the introduction
Bibliographic Code:
2014arXiv1407.1867E

Abstract

We present a simple algebraic construction of all the small resolutions for the SU(5) Weierstrass model. Each resolution corresponds to a subchamber on the Coulomb branch of the five-dimensional N=1 SU(5) gauge theory with matter fields in the fundamental and two-index antisymmetric representations. This construction unifies all previous resolutions found in the literature in a single framework.

 

Title:
Exactly isochoric deformations of soft solids
Authors:
Biggins, J. S.; Wei, Z.; Mahadevan, L.
Publication:
eprint arXiv:1407.2021
Publication Date:
07/2014
Origin:
ARXIV
Keywords:
Condensed Matter - Soft Condensed Matter, Condensed Matter - Materials Science, Physics - Biological Physics, Physics - Fluid Dynamics
Bibliographic Code:
2014arXiv1407.2021B

Abstract

Many materials of contemporary interest, such as gels, biological tissues and elastomers, are easily deformed but essentially incompressible. Traditional linear theory of elasticity implements incompressibility only to first order and thus permits some volume changes, which become problematically large even at very small strains. Using a mixed coordinate transformation originally due to Gauss, we enforce the constraint of isochoric deformations exactly to develop a linear theory with perfect volume conservation that remains valid until strains become geometrically large. We demonstrate the utility of this approach by calculating the response of an infinite soft isochoric solid to a point force that leads to a nonlinear generalization of the Kelvin solution. Our approach naturally generalizes to a range of problems involving deformations of soft solids and interfaces in 2 dimensional and axisymmetric geometries, which we exemplify by determining the solution to a distributed load that mimics muscular contraction within the bulk of a soft solid.

 

Title:
Quantifying the power of multiple event interpretations
Authors:
Chien, Yang-Ting; Farhi, David; Krohn, David; Marantan, Andrew; Lopez Mateos, David; Schwartz, Matthew
Publication:
eprint arXiv:1407.2892
Publication Date:
07/2014
Origin:
ARXIV
Keywords:
High Energy Physics - Phenomenology, High Energy Physics - Experiment
Comment:
13 pages, 2 figures
Bibliographic Code:
2014arXiv1407.2892C

Abstract

A number of methods have been proposed recently which exploit multiple highly-correlated interpretations of events, or of jets within an event. For example, Qjets reclusters a jet multiple times and telescoping jets uses multiple cone sizes. Previous work has employed these methods in pseudo-experimental analyses and found that, with a simplified statistical treatment, they give sizable improvements over traditional methods. In this paper, the improvement gain from multiple event interpretations is explored with methods much closer to those used in real experiments. To this end, we derive a generalized extended maximum likelihood procedure. We study the significance improvement in Higgs to bb with both this method and the simplified method from previous analysis. With either method, we find that using multiple jet radii can provide substantial benefit over a single radius. Another concern we address is that multiple event interpretations might be exploiting similar information to that already present in the standard kinematic variables. By examining correlations between kinematic variables commonly used in LHC analyses and invariant masses obtained with multiple jet reconstructions, we find that using multiple radii is still helpful even on top of standard kinematic variables when combined with boosted decision trees. These results suggest that including multiple event interpretations in a realistic search for Higgs to bb would give additional sensitivity over traditional approaches.

 

Title:
Deconfined criticality in bilayer graphene
Authors:
Lee, Junhyun; Sachdev, Subir
Publication:
eprint arXiv:1407.2936
Publication Date:
07/2014
Origin:
ARXIV
Keywords:
Condensed Matter - Strongly Correlated Electrons, Condensed Matter - Mesoscale and Nanoscale Physics
Comment:
22 pages, 7 figures
Bibliographic Code:
2014arXiv1407.2936L

Abstract

We propose that bilayer graphene can provide an experimental realization of deconfined criticality. Current experiments indicate the presence of N\'{e}el order in the presence of a moderate magnetic field. The N\'{e}el order can be destabilized by application of a transverse electric field. The resulting electric field induced state is likely to have valence bond solid order, and the transition can acquire the emergent fractionalized and gauge excitations of deconfined criticality.

 

Title:
Atomic-scale nuclear spin imaging using quantum-assisted sensors in diamond
Authors:
Ajoy, Ashok; Bissbort, Ulf; Lukin, Mikhail D.; Walsworth, Ronald L.; Cappellaro, Paola
Publication:
eprint arXiv:1407.3134
Publication Date:
07/2014
Origin:
ARXIV
Keywords:
Quantum Physics, Condensed Matter - Other Condensed Matter
Comment:
Contains supplementary material
Bibliographic Code:
2014arXiv1407.3134A

Abstract

Nuclear spin imaging at the atomic level is essential for the understanding of fundamental biological phenomena and for applications such as drug discovery. The advent of novel nano-scale sensors has given hope of achieving the long-standing goal of single-protein, high spatial-resolution structure determination in their natural environment and ambient conditions. In particular, quantum sensors based on the spin-dependent photoluminescence of Nitrogen Vacancy (NV) centers in diamond have recently been used to detect nanoscale ensembles of external nuclear spins. While NV sensitivity is approaching single-spin levels, extracting relevant information from a very complex structure is a further challenge, since it requires not only the ability to sense the magnetic field of an isolated nuclear spin, but also to achieve atomic-scale spatial resolution. Here we propose a method that, by exploiting the coupling of the NV center to an intrinsic quantum memory associated with the Nitrogen nuclear spin, can reach a tenfold improvement in spatial resolution, down to atomic scales. The spatial resolution enhancement is achieved through coherent control of the sensor spin, which creates a dynamic frequency filter selecting only a few nuclear spins at a time. We propose and analyze a protocol that would allow not only sensing individual spins in a complex biomolecule, but also unraveling couplings among them, thus elucidating local characteristics of the molecule structure.

 

Title:
Comment on "Symmetry classification of bond order parameters in cuprates"
Authors:
Allais, Andrea; Bauer, Johannes; Sachdev, Subir
Publication:
eprint arXiv:1407.3281
Publication Date:
07/2014
Origin:
ARXIV
Keywords:
Condensed Matter - Strongly Correlated Electrons, Condensed Matter - Superconductivity
Comment:
10 pages, 4 figures
Bibliographic Code:
2014arXiv1407.3281A

Abstract

We review the transformation of bond order waves with non-trivial form factors under time-reversal and point group symmetry. Zeyher (arXiv:1406.6846) argues that certain d-form factor states must be "flux states", but this does not apply to the form factors as defined by us (arXiv:1402.4807). The latter definitions were used in the experimental detection (arXiv:1402.5415, arXiv:1404.0362).

 

Title:
Studies of high-transverse momentum jet substructure and top quarks produced in 1.96 TeV proton-antiproton collisions
Authors:
Aaltonen, T.; Alon, R.; Amerio, S.;... Franklin, M.;... Guimaraes da Costa, J.;... and 401 coauthors
Publication:
eprint arXiv:1407.3484
Publication Date:
07/2014
Origin:
ARXIV
Keywords:
High Energy Physics - Experiment
Comment:
51 pages, to be submitted to Physical Review D
Bibliographic Code:
2014arXiv1407.3484A

Abstract

Results of a study of the substructure of the highest transverse momentum (pT) jets observed by the CDF collaboration are presented. Events containing at least one jet with pT > 400 GeV/c in a sample corresponding to an integrated luminosity of 5.95 inverse fb, collected in 1.96 TeV proton-antiproton collisions at the Fermilab Tevatron collider, are selected. A study of the jet mass, angularity, and planar-flow distributions is presented, and the measurements are compared with predictions of perturbative quantum chromodynamics. A search for boosted top-quark production is also described, leading to a 95% confidence level upper limit of 38 fb on the production cross section of top quarks with pT > 400 GeV/c.

 

Title:
New Symmetries of Massless QED
Authors:
He, Temple; Mitra, Prahar; Porfyriadis, Achilleas P.; Strominger, Andrew
Publication:
eprint arXiv:1407.3789
Publication Date:
07/2014
Origin:
ARXIV
Keywords:
High Energy Physics - Theory, General Relativity and Quantum Cosmology, High Energy Physics - Phenomenology
Comment:
17 pages
Bibliographic Code:
2014arXiv1407.3789H

Abstract

An infinite number of physically nontrivial symmetries are found for abelian gauge theories with massless charged particles. They are generated by large $U(1)$ gauge transformations that asymptotically approach an arbitrary function $\varepsilon(z,\bar{z})$ on the conformal sphere at future null infinity ($\mathscr I^+$) but are independent of the retarded time. The value of $\varepsilon$ at past null infinity ($\mathscr I^-$) is determined from that on $\mathscr I^+$ by the condition that it take the same value at either end of any light ray crossing Minkowski space. The $\varepsilon\neq$ constant symmetries are spontaneously broken in the usual vacuum. The associated Goldstone modes are zero-momentum photons and comprise a $U(1)$ boson living on the conformal sphere. The Ward identity associated with this asymptotic symmetry is shown to be the abelian soft photon theorem.

 

Title:
Low's Subleading Soft Theorem as a Symmetry of QED
Authors:
Lysov, Vyacheslav; Pasterski, Sabrina; Strominger, Andrew
Publication:
eprint arXiv:1407.3814
Publication Date:
07/2014
Origin:
ARXIV
Keywords:
High Energy Physics - Theory, High Energy Physics - Phenomenology
Comment:
11 pages
Bibliographic Code:
2014arXiv1407.3814L

Abstract

It was shown by F. Low in the 1950s that the subleading terms of soft photon S-matrix elements obey a universal linear relation. In this paper we give a new interpretation to this old relation, for the case of massless QED, as an infinitesimal symmetry of the S-matrix. The symmetry is shown to be locally generated by a vector field on the conformal sphere at null infinity. Explicit expressions are constructed for the associated charges as integrals over null infinity and shown to generate the symmetry. These charges are local generalizations of electric and magnetic dipole charges.

 

Title:
Probing Competing and Intertwined Orders with Resonant Inelastic x-ray Scattering in the Hole-Doped Cuprates
Authors:
Benjamin, David; Klich, Israel; Demler, Eugene
Publication:
eprint arXiv:1407.3843
Publication Date:
07/2014
Origin:
ARXIV
Keywords:
Condensed Matter - Strongly Correlated Electrons
Comment:
8 pages
Bibliographic Code:
2014arXiv1407.3843B

Abstract

We develop a formalism to study indirect resonant inelastic x-ray scattering (RIXS) in systems with itinerant electrons, accounting for the attraction between valence electrons and the positively-charged core hole exactly, and apply this formalism to the hole-doped cuprate superconductors. We focus on the relationship between RIXS lineshapes and band structure, including broken symmetries. We show that RIXS is capable of distinguishing between competing order parameters, establishing it as a useful probe of the pseudogap phase.

 

Title:
Measurement of the Single Top Quark Production Cross Section and |Vtb| in Events with One Charged Lepton, Large Missing Transverse Energy, and Jets at CDF
Authors:
CDF Collaboration; Aaltonen, T.; Amerio, S.; Amidei, D.; ... Franklin, M.;... Guimaraes da Costa, J.;... .; and 396 coauthors
Publication:
eprint arXiv:1407.4031
Publication Date:
07/2014
Origin:
ARXIV
Keywords:
High Energy Physics - Experiment
Comment:
Submitted to Physical Review Letters
Bibliographic Code:
2014arXiv1407.4031C

Abstract

We report a measurement of single top quark production in proton-antiproton collisions at a center-of-mass energy of \sqrt{s} = 1.96 TeV using a data set corresponding to 7.5 fb-1 of integrated luminosity collected by the Collider Detector at Fermilab. We select events consistent with the single top quark decay process t \to Wb \to l{\nu}b by requiring the presence of an electron or muon, a large imbalance of transverse momentum indicating the presence of a neutrino, and two or three jets including at least one originating from a bottom quark. An artificial neural network is used to discriminate the signal from backgrounds. We measure a single top quark production cross section of 3.04+0.57-0.53 pb and set a lower limit on the magnitude of the coupling between the top quark and bottom quark |Vtb| > 0.78 at the 95% credibility level.

 

Title:
Slow, Continuous Beams of Large Gas Phase Molecules
Authors:
Patterson, David; Doyle, John M.
Publication:
eprint arXiv:1407.4823
Publication Date:
07/2014
Origin:
ARXIV
Keywords:
Physics - Chemical Physics
Bibliographic Code:
2014arXiv1407.4823P

Abstract

Cold, continuous, high flux beams of benzonitrile, fluorobenzine, and anisole have been created. Buffer-gas cooling with a cryogenic gas provides the cooling and slow forward beam velocities. The beam of benzonitrile was measured to have a forward velocity peaked at 67 $\pm 5$ m s$^{-1}$, and a continuous flux of $10^{15}$ molecules s$^{-1}$. These beams provide a continuous source for high resolution spectroscopy, and provide an attractive starting point for further spatial manipulation of such molecules, including eventual trapping.

 

Title:
BICEP3: a 95 GHz refracting telescope for degree-scale CMB polarization
Authors:
Ahmed, Z.; Amiri, M.; Benton, S. J.; Bock, J. J.; Bowens-Rubin, R.; Buder, I.; Bullock, E.; Connors, J.; Filippini, J. P.; Grayson, J. A.; Halpern, M.; Hilton, G. C.; Hristov, V. V.; Hui, H.; Irwin, K. D.; Kang, J.; Karkare, K. S.; Karpel, E.; Kovac, J. M.; Kuo, C. L.; Netterfield, C. B.; Nguyen, H. T.; O'Brient, R.; Ogburn, R. W., IV; Pryke, C.; Reintsema, C. D.; Richter, S.; Thompson, K. L.; Turner, A. D.; Vieregg, A. G.; Wu, W. L. K.; Yoon, K. W.
Publication:
eprint arXiv:1407.5928
Publication Date:
07/2014
Origin:
ARXIV
Keywords:
Astrophysics - Instrumentation and Methods for Astrophysics, Astrophysics - Cosmology and Nongalactic Astrophysics
Comment:
12 pages, 5 figures. Presented at SPIE Astronomical Telescopes and Instrumentation 2014: Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy VII. To be published in Proceedings of SPIE Volume 9153
Bibliographic Code:
2014arXiv1407.5928A

Abstract

BICEP3 is a 550 mm-aperture refracting telescope for polarimetry of radiation in the cosmic microwave background at 95 GHz. It adopts the methodology of BICEP1, BICEP2 and the Keck Array experiments - it possesses sufficient resolution to search for signatures of the inflation-induced cosmic gravitational-wave background while utilizing a compact design for ease of construction and to facilitate the characterization and mitigation of systematics. However, BICEP3 represents a significant breakthrough in per-receiver sensitivity, with a focal plane area 5$\times$ larger than a BICEP2/Keck Array receiver and faster optics ($f/1.6$ vs. $f/2.4$). Large-aperture infrared-reflective metal-mesh filters and infrared-absorptive cold alumina filters and lenses were developed and implemented for its optics. The camera consists of 1280 dual-polarization pixels; each is a pair of orthogonal antenna arrays coupled to transition-edge sensor bolometers and read out by multiplexed SQUIDs. Upon deployment at the South Pole during the 2014-15 season, BICEP3 will have survey speed comparable to Keck Array 150 GHz (2013), and will significantly enhance spectral separation of primordial B-mode power from that of possible galactic dust contamination in the BICEP2 observation patch.

 

Title:
6d Conformal Matter
Authors:
Del Zotto, Michele; Heckman, Jonathan J.; Tomasiello, Alessandro; Vafa, Cumrun
Publication:
eprint arXiv:1407.6359
Publication Date:
07/2014
Origin:
ARXIV
Keywords:
High Energy Physics - Theory
Comment:
61 pages, 28 figures
Bibliographic Code:
2014arXiv1407.6359D

Abstract

A single M5-brane probing G, an ADE-type singularity, leads to a system which has G x G global symmetry and can be viewed as "bifundamental" (G,G) matter. For the A_N series, this leads to the usual notion of bifundamental matter. For the other cases it corresponds to a strongly interacting (1,0) superconformal system in six dimensions. Similarly, an ADE singularity intersecting the Horava-Witten wall leads to a superconformal matter system with E_8 x G global symmetry. Using the F-theory realization of these theories, we elucidate the Coulomb/tensor branch of (G,G') conformal matter. This leads to the notion of fractionalization of an M5-brane on an ADE singularity as well as fractionalization of the intersection point of the ADE singularity with the Horava-Witten wall. Partial Higgsing of these theories leads to new 6d SCFTs in the infrared, which we also characterize. This generalizes the class of (1,0) theories which can be perturbatively realized by suspended branes in IIA string theory. By reducing on a circle, we arrive at novel duals for 5d affine quiver theories. Introducing many M5-branes leads to large N gravity duals.

 

Title:
Far-from-equilibrium spin transport in Heisenberg quantum magnets
Authors:
Hild, Sebastian; Fukuhara, Takeshi; Schauß, Peter; Zeiher, Johannes; Knap, Michael; Demler, Eugene; Bloch, Immanuel; Gross, Christian
Publication:
eprint arXiv:1407.6934
Publication Date:
07/2014
Origin:
ARXIV
Keywords:
Condensed Matter - Quantum Gases, Condensed Matter - Strongly Correlated Electrons
Bibliographic Code:
2014arXiv1407.6934H

Abstract

We study experimentally the far-from-equilibrium dynamics in ferromagnetic Heisenberg quantum magnets realized with ultracold atoms in an optical lattice. After controlled imprinting of a spin spiral pattern with adjustable wave vector, we measure the decay of the initial spin correlations through single-site resolved detection. On the experimentally accessible timescale of several exchange times we find a profound dependence of the decay rate on the wave vector. In one-dimensional systems we observe diffusion-like spin transport with a dimensionless diffusion coefficient of 0.22(1). We show how this behavior emerges from the microscopic properties of the closed quantum system. In contrast to the one-dimensional case, our transport measurements for two-dimensional Heisenberg systems indicate anomalous super-diffusion.

 

Title:
Little String Amplitudes (and the Unreasonable Effectiveness of 6D SYM)
Authors:
Chang, Chi-Ming; Lin, Ying-Hsuan; Shao, Shu-Heng; Wang, Yifan; Yin, Xi
Publication:
eprint arXiv:1407.7511
Publication Date:
07/2014
Origin:
ARXIV
Keywords:
High Energy Physics - Theory
Comment:
58 pages, 5 figures, 3 tables, footnotes added, reference added
Bibliographic Code:
2014arXiv1407.7511C

Abstract

We study tree level scattering amplitudes of four massless states in the double scaled little string theory, and compare them to perturbative loop amplitudes in six-dimensional super-Yang-Mills theory. The little string amplitudes are computed from correlators in the cigar coset CFT and in N=2 minimal models. The results are expressed in terms of integrals of conformal blocks and evaluated numerically in the alpha' expansion. We find striking agreements with up to 2-loop scattering amplitudes of massless gluons in 6D SU(k) SYM at a Z_k invariant point on the Coulomb branch. We comment on the issue of UV divergence at higher loop orders in the gauge theory and discuss the implication of our results.

 

Title:
Invariant Solutions to the Strominger System on Complex Lie Groups and Their Quotients
Authors:
Fei, Teng; Yau, Shing-Tung
Publication:
eprint arXiv:1407.7641
Publication Date:
07/2014
Origin:
ARXIV
Keywords:
Mathematical Physics, Mathematics - Differential Geometry
Comment:
11 pages
Bibliographic Code:
2014arXiv1407.7641F

Abstract

Using canonical 1-parameter family of Hermitian connections on the tangent bundle, we provide invariant solutions to the Strominger system on complex Lie groups. Both flat and non-flat cases are discussed in great detail.

 

Title:
Discovery of eight z ~ 6 quasars from pan-STARRS1
Authors:
Bañados, E.; Venemans, B.P.; Morganson, E.; Decarli, R.; Walter, F.; Chambers, K.C.; Rix, H.-W.; Farina, E.P.; Fan, X.; Jiang, L.; McGreer, I.; De Rosa, G.; Simcoe, R.; Weiss, A.; Price, P.A.; Morgan, J.S.; Burgett, W.S.; Greiner, J.; Kaiser, N.; Kudritzki, R.-P.; Magnier, E.A.; Metcalfe, N.; Stubbs, C.W.; Sweeney, W.; Tonry, J.L.; Wainscoat, R.J.; Waters, C.
Publication:
Astronomical Journal vol.148, no.1, 14 (12 pp.). ISSN: 1538-3881
Publication Date:
07/2014
Publisher:
IOP
Database:
Inspec
Inspec Headings:
astronomical spectra; black holes; cosmology; quasars; red shift; statistical analysis
DOI:
10.1088/0004-6256/148/1/14

Abstract

High-redshift quasars are currently the only probes of the growth of supermassive black holes and potential tracers of structure evolution at early cosmic time. Here we present our candidate selection criteria from the Panoramic Survey Telescope & Rapid Response System 1 and follow-up strategy to discover quasars in the redshift range 5.7 ≤ z ≤ 6.2. With this strategy we discovered eight new 5.7≤ z ≤6.0 quasars, increasing the number of known quasars at z > 5.7 by more than 10%. We additionally recovered 18 previously known quasars. The eight quasars presented here span a large range of luminosities (-27.3 ≤ M1450 ≤ -25.4; 19.6 ≤ zP1 ≤ 21.2) and are remarkably heterogeneous in their spectral features: half of them show bright emission lines whereas the other half show a weak or no Lyα emission line (25% with rest-frame equivalent width of the Lyα+N v line lower than 15 Å). We find a larger fraction of weak-line emission quasars than in lower redshift studies. This may imply that the weak-line quasar population at the highest redshifts could be more abundant than previously thought. However, larger samples of quasars are needed to increase the statistical significance of this finding.

 

Title:
A high-throughput cellulase screening system based on droplet microfluidics
Authors:
Ostafe, R.; Prodanovic, R.; Lloyd Ung, W.; Weitz, D.A.; Fischer, R.
Publication:
Biomicrofluidics vol.8, no.4, 041102
Publication Date:
07/2014
Publisher:
APS
Database:
Inspec
Inspec Headings:
biochemistry; biological techniques; bioMEMS; cellular biophysics;  drops; enzymes;  fluorescence;  lab-on-a-chip; microfluidics; molecular biophysics; spectrochemical analysis
DOI:
10.1063/1.4886771

Abstract

A new ultra-high-throughput screening assay for the detection of cellulase activity was developed based on microfluidic sorting. Cellulase activity is detected using a series of coupled enzymes leading to the formation of a fluorescent product that can be detected on a chip. Using this method, we have achieved up to 300-fold enrichments of the active population of cells and greater than 90% purity after just one sorting round. In addition, we proved that we can sort the cellulase-expressing cells from mixtures containing less than 1% active cells.


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