M. Wendt - AIP Potsdam

M. Wendt
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Name
M. Wendt
Affiliation
AIP Potsdam
City
Potsdam
Country
Germany

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Physics - Accelerator Physics (17)
 
Mathematics - K-Theory and Homology (13)
 
Astrophysics of Galaxies (9)
 
Mathematics - Algebraic Geometry (8)
 
Cosmology and Nongalactic Astrophysics (7)
 
Mathematics - Algebraic Topology (6)
 
Solar and Stellar Astrophysics (2)
 
Mathematics - Representation Theory (1)
 
General Relativity and Quantum Cosmology (1)
 
High Energy Physics - Phenomenology (1)
 
Instrumentation and Methods for Astrophysics (1)
 
Mathematics - Commutative Algebra (1)
 
Mathematics - Rings and Algebras (1)
 
Mathematics - Group Theory (1)
 
High Energy Physics - Experiment (1)

Publications Authored By M. Wendt

The paper discusses stably trivial torsors for spin and orthogonal groups over smooth affine schemes over infinite perfect fields of characteristic unequal to 2. We give a complete description of all the invariants relevant for the classification of such objects over schemes of dimension at most $3$, along with many examples. The results are based on the $\mathbb{A}^1$-representability theorem for torsors and transfer of known computations of $\mathbb{A}^1$-homotopy sheaves along the sporadic isomorphisms to spin groups. Read More

We study generically split octonion algebras over schemes using techniques of ${\mathbb A}^1$-homotopy theory. By combining affine representability results with techniques of obstruction theory, we establish classification results over smooth affine schemes of small dimension. In particular, for smooth affine schemes over algebraically closed fields, we show that generically split octonion algebras may be classified by characteristic classes including the second Chern class and another "mod $3$" invariant. Read More

For every prime $p$, Mohan Kumar constructed examples of stably free modules of rank $p$ on suitable $(p+1)$-dimensional smooth affine varieties. This note discusses how to detect the corresponding unimodular rows in motivic cohomology. Using the recent developments in the $\mathbb{A}^1$-obstruction classification of vector bundles, this provides an alternative proof of non-triviality of Mohan Kumar's stably free modules. Read More

We compute the Chow-Witt rings of the classifying spaces for the symplectic and special linear groups. In the structural description we give, contributions from real and complex realization are clearly visible. In particular, the computation of cohomology with $\mathbf{I}^j$-coefficients is done closely along the lines of Brown's computation of integral cohomology for special orthogonal groups. Read More

Emission signatures from galactic winds provide an opportunity to directly map the outflowing gas, but this is traditionally challenging because of the low surface brightness. Using deep observations (27 hours) of the Hubble Deep Field South from the Multi Unit Spectroscopic Explorer (MUSE) instrument, we identify signatures of an outflow in both emission and absorption from a spatially resolved galaxy at z = 1.29 with a stellar mass M* = 8 x 10^9 Msun, star formation rate SFR = 77 Msun/yr, and star formation rate surface brightness 1. Read More

To characterize the absorption properties of this circumgalactic medium (CGM) and its relation to the LG we present the so-far largest survey of metal absorption in Galactic high-velocity clouds (HVCs) using archival ultraviolet (UV) spectra of extragalactic background sources. The UV data are obtained with the Cosmic Origins Spectrograph (COS) onboard the Hubble Space Telescope (HST) and are supplemented by 21 cm radio observations of neutral hydrogen. Along 262 sightlines we measure metal absorption in the lines of SiII, SiIII, CII, and CIV and associated HI 21 cm emission in HVCs in the velocity range |v_LSR|=100-500 km s^-1. Read More

We provide some new computations of Farrell--Tate and Bredon (co)homology for arithmetic groups. For calculations of Farrell-Tate or Bredon homology, one needs cell complexes where cell stabilizers fix their cells pointwise. We provide an algorithm computing an efficient subdivision of a complex to achieve this rigidity property. Read More

The paper provides a computation of the additive structure as well as a partial description of the Chern-class module structure of the cohomology of $GL_3$ over the function ring of an elliptic curve over a finite field. The computation is achieved by a detailed analysis of the isotropy spectral sequence for the action of $GL_3$ on the associated Bruhat-Tits building. This provides insights into the function field version of Quillen's conjecture on the structure of cohomology rings of arithmetic groups. Read More

2016Aug
Authors: The CLIC, CLICdp collaborations, :, M. J. Boland, U. Felzmann, P. J. Giansiracusa, T. G. Lucas, R. P. Rassool, C. Balazs, T. K. Charles, K. Afanaciev, I. Emeliantchik, A. Ignatenko, V. Makarenko, N. Shumeiko, A. Patapenka, I. Zhuk, A. C. Abusleme Hoffman, M. A. Diaz Gutierrez, M. Vogel Gonzalez, Y. Chi, X. He, G. Pei, S. Pei, G. Shu, X. Wang, J. Zhang, F. Zhao, Z. Zhou, H. Chen, Y. Gao, W. Huang, Y. P. Kuang, B. Li, Y. Li, J. Shao, J. Shi, C. Tang, X. Wu, L. Ma, Y. Han, W. Fang, Q. Gu, D. Huang, X. Huang, J. Tan, Z. Wang, Z. Zhao, T. Laštovička, U. Uggerhoj, T. N. Wistisen, A. Aabloo, K. Eimre, K. Kuppart, S. Vigonski, V. Zadin, M. Aicheler, E. Baibuz, E. Brücken, F. Djurabekova, P. Eerola, F. Garcia, E. Haeggström, K. Huitu, V. Jansson, V. Karimaki, I. Kassamakov, A. Kyritsakis, S. Lehti, A. Meriläinen, R. Montonen, T. Niinikoski, K. Nordlund, K. Österberg, M. Parekh, N. A. Törnqvist, J. Väinölä, M. Veske, W. Farabolini, A. Mollard, O. Napoly, F. Peauger, J. Plouin, P. Bambade, I. Chaikovska, R. Chehab, M. Davier, W. Kaabi, E. Kou, F. LeDiberder, R. Pöschl, D. Zerwas, B. Aimard, G. Balik, J. -P. Baud, J. -J. Blaising, L. Brunetti, M. Chefdeville, C. Drancourt, N. Geoffroy, J. Jacquemier, A. Jeremie, Y. Karyotakis, J. M. Nappa, S. Vilalte, G. Vouters, A. Bernard, I. Peric, M. Gabriel, F. Simon, M. Szalay, N. van der Kolk, T. Alexopoulos, E. N. Gazis, N. Gazis, E. Ikarios, V. Kostopoulos, S. Kourkoulis, P. D. Gupta, P. Shrivastava, H. Arfaei, M. K. Dayyani, H. Ghasem, S. S. Hajari, H. Shaker, Y. Ashkenazy, H. Abramowicz, Y. Benhammou, O. Borysov, S. Kananov, A. Levy, I. Levy, O. Rosenblat, G. D'Auria, S. Di Mitri, T. Abe, A. Aryshev, T. Higo, Y. Makida, S. Matsumoto, T. Shidara, T. Takatomi, Y. Takubo, T. Tauchi, N. Toge, K. Ueno, J. Urakawa, A. Yamamoto, M. Yamanaka, R. Raboanary, R. Hart, H. van der Graaf, G. Eigen, J. Zalieckas, E. Adli, R. Lillestøl, L. Malina, J. Pfingstner, K. N. Sjobak, W. Ahmed, M. I. Asghar, H. Hoorani, S. Bugiel, R. Dasgupta, M. Firlej, T. A. Fiutowski, M. Idzik, M. Kopec, M. Kuczynska, J. Moron, K. P. Swientek, W. Daniluk, B. Krupa, M. Kucharczyk, T. Lesiak, A. Moszczynski, B. Pawlik, P. Sopicki, T. Wojtoń, L. Zawiejski, J. Kalinowski, M. Krawczyk, A. F. Żarnecki, E. Firu, V. Ghenescu, A. T. Neagu, T. Preda, I-S. Zgura, A. Aloev, N. Azaryan, J. Budagov, M. Chizhov, M. Filippova, V. Glagolev, A. Gongadze, S. Grigoryan, D. Gudkov, V. Karjavine, M. Lyablin, A. Olyunin, A. Samochkine, A. Sapronov, G. Shirkov, V. Soldatov, A. Solodko, E. Solodko, G. Trubnikov, I. Tyapkin, V. Uzhinsky, A. Vorozhtov, E. Levichev, N. Mezentsev, P. Piminov, D. Shatilov, P. Vobly, K. Zolotarev, I. Bozovic Jelisavcic, G. Kacarevic, S. Lukic, G. Milutinovic-Dumbelovic, M. Pandurovic, U. Iriso, F. Perez, M. Pont, J. Trenado, M. Aguilar-Benitez, J. Calero, L. Garcia-Tabares, D. Gavela, J. L. Gutierrez, D. Lopez, F. Toral, D. Moya, A. Ruiz Jimeno, I. Vila, T. Argyropoulos, C. Blanch Gutierrez, M. Boronat, D. Esperante, A. Faus-Golfe, J. Fuster, N. Fuster Martinez, N. Galindo Muñoz, I. García, J. Giner Navarro, E. Ros, M. Vos, R. Brenner, T. Ekelöf, M. Jacewicz, J. Ögren, M. Olvegård, R. Ruber, V. Ziemann, D. Aguglia, N. Alipour Tehrani, A. Andersson, F. Andrianala, F. Antoniou, K. Artoos, S. Atieh, R. Ballabriga Sune, M. J. Barnes, J. Barranco Garcia, H. Bartosik, C. Belver-Aguilar, A. Benot Morell, D. R. Bett, S. Bettoni, G. Blanchot, O. Blanco Garcia, X. A. Bonnin, O. Brunner, H. Burkhardt, S. Calatroni, M. Campbell, N. Catalan Lasheras, M. Cerqueira Bastos, A. Cherif, E. Chevallay, B. Constance, R. Corsini, B. Cure, S. Curt, B. Dalena, D. Dannheim, G. De Michele, L. De Oliveira, N. Deelen, J. P. Delahaye, T. Dobers, S. Doebert, M. Draper, F. Duarte Ramos, A. Dubrovskiy, K. Elsener, J. Esberg, M. Esposito, V. Fedosseev, P. Ferracin, A. Fiergolski, K. Foraz, A. Fowler, F. Friebel, J-F. Fuchs, C. A. Fuentes Rojas, A. Gaddi, L. Garcia Fajardo, H. Garcia Morales, C. Garion, L. Gatignon, J-C. Gayde, H. Gerwig, A. N. Goldblatt, C. Grefe, A. Grudiev, F. G. Guillot-Vignot, M. L. Gutt-Mostowy, M. Hauschild, C. Hessler, J. K. Holma, E. Holzer, M. Hourican, D. Hynds, Y. Inntjore Levinsen, B. Jeanneret, E. Jensen, M. Jonker, M. Kastriotou, J. M. K. Kemppinen, R. B. Kieffer, W. Klempt, O. Kononenko, A. Korsback, E. Koukovini Platia, J. W. Kovermann, C-I. Kozsar, I. Kremastiotis, S. Kulis, A. Latina, F. Leaux, P. Lebrun, T. Lefevre, L. Linssen, X. Llopart Cudie, A. A. Maier, H. Mainaud Durand, E. Manosperti, C. Marelli, E. Marin Lacoma, R. Martin, S. Mazzoni, G. Mcmonagle, O. Mete, L. M. Mether, M. Modena, R. M. Münker, T. Muranaka, E. Nebot Del Busto, N. Nikiforou, D. Nisbet, J-M. Nonglaton, F. X. Nuiry, A. Nürnberg, M. Olvegard, J. Osborne, S. Papadopoulou, Y. Papaphilippou, A. Passarelli, M. Patecki, L. Pazdera, D. Pellegrini, K. Pepitone, E. Perez Codina, A. Perez Fontenla, T. H. B. Persson, M. Petrič, F. Pitters, S. Pittet, F. Plassard, R. Rajamak, S. Redford, Y. Renier, S. F. Rey, G. Riddone, L. Rinolfi, E. Rodriguez Castro, P. Roloff, C. Rossi, V. Rude, G. Rumolo, A. Sailer, E. Santin, D. Schlatter, H. Schmickler, D. Schulte, N. Shipman, E. Sicking, R. Simoniello, P. K. Skowronski, P. Sobrino Mompean, L. Soby, M. P. Sosin, S. Sroka, S. Stapnes, G. Sterbini, R. Ström, I. Syratchev, F. Tecker, P. A. Thonet, L. Timeo, H. Timko, R. Tomas Garcia, P. Valerio, A. L. Vamvakas, A. Vivoli, M. A. Weber, R. Wegner, M. Wendt, B. Woolley, W. Wuensch, J. Uythoven, H. Zha, P. Zisopoulos, M. Benoit, M. Vicente Barreto Pinto, M. Bopp, H. H. Braun, M. Csatari Divall, M. Dehler, T. Garvey, J. Y. Raguin, L. Rivkin, R. Zennaro, A. Aksoy, Z. Nergiz, E. Pilicer, I. Tapan, O. Yavas, V. Baturin, R. Kholodov, S. Lebedynskyi, V. Miroshnichenko, S. Mordyk, I. Profatilova, V. Storizhko, N. Watson, A. Winter, J. Goldstein, S. Green, J. S. Marshall, M. A. Thomson, B. Xu, W. A. Gillespie, R. Pan, M. A Tyrk, D. Protopopescu, A. Robson, R. Apsimon, I. Bailey, G. Burt, D. Constable, A. Dexter, S. Karimian, C. Lingwood, M. D. Buckland, G. Casse, J. Vossebeld, A. Bosco, P. Karataev, K. Kruchinin, K. Lekomtsev, L. Nevay, J. Snuverink, E. Yamakawa, V. Boisvert, S. Boogert, G. Boorman, S. Gibson, A. Lyapin, W. Shields, P. Teixeira-Dias, S. West, R. Jones, N. Joshi, R. Bodenstein, P. N. Burrows, G. B. Christian, D. Gamba, C. Perry, J. Roberts, J. A. Clarke, N. A. Collomb, S. P. Jamison, B. J. A. Shepherd, D. Walsh, M. Demarteau, J. Repond, H. Weerts, L. Xia, J. D. Wells, C. Adolphsen, T. Barklow, M. Breidenbach, N. Graf, J. Hewett, T. Markiewicz, D. McCormick, K. Moffeit, Y. Nosochkov, M. Oriunno, N. Phinney, T. Rizzo, S. Tantawi, F. Wang, J. Wang, G. White, M. Woodley

The Compact Linear Collider (CLIC) is a multi-TeV high-luminosity linear e+e- collider under development. For an optimal exploitation of its physics potential, CLIC is foreseen to be built and operated in a staged approach with three centre-of-mass energy stages ranging from a few hundred GeV up to 3 TeV. The first stage will focus on precision Standard Model physics, in particular Higgs and top-quark measurements. Read More

We study the $z\approx3.5$ intergalactic medium (IGM) by comparing new, high-quality absorption spectra of eight QSOs with $\langle z_{\rm QSO} \rangle=3.75$, to virtual observations of the EAGLE cosmological hydrodynamical simulations. Read More

The physical properties of galactic winds are one of the keys to understand galaxy formation and evolution. These properties can be constrained thanks to background quasar lines of sight (LOS) passing near star-forming galaxies (SFGs). We present the first results of the MusE GAs FLOw and Wind (MEGAFLOW) survey obtained of 2 quasar fields which have 8 MgII absorbers of which 3 have rest-equivalent width greater than 0. Read More

We present a detailed analysis of the kinematics of the Galactic globular cluster NGC 6397 based on more than ~18,000 spectra obtained with the novel integral field spectrograph MUSE. While NGC 6397 is often considered a core collapse cluster, our analysis suggests a flattening of the surface brightness profile at the smallest radii. Although it is among the nearest globular clusters, the low velocity dispersion of NGC 6397 of <5km/s imposes heavy demands on the quality of the kinematical data. Read More

Aims. We demonstrate the high multiplex advantage of crowded field 3D spectroscopy using the new integral field spectrograph MUSE by means of a spectroscopic analysis of more than 12,000 individual stars in the globular cluster NGC 6397. Methods. Read More

We use a background quasar to detect the presence of circum-galactic gas around a $z=0.91$ low-mass star forming galaxy. Data from the new Multi Unit Spectroscopic Explorer (MUSE) on the VLT show that the host galaxy has a dust-corrected star-formation rate (SFR) of 4. Read More

We report the detection of extended Ly alpha emission around individual star-forming galaxies at redshifts z = 3-6 in an ultradeep exposure of the Hubble Deep Field South obtained with MUSE on the ESO-VLT. The data reach a limiting surface brightness (1sigma) of ~1 x 10^-19 erg s^-1 cm^-2 arcsec^-2 in azimuthally averaged radial profiles, an order of magnitude improvement over previous narrowband imaging. Our sample consists of 26 spectroscopically confirmed Ly alpha-emitting, but mostly continuum-faint (m_AB >~ 27) galaxies. Read More

We establish a relative version of the abstract "affine representability" theorem in ${\mathbb A}^1$-homotopy theory from Part I (1506.07093) of this paper. We then prove some ${\mathbb A}^1$-invariance statements for generically trivial torsors under isotropic reductive groups over infinite fields analogous to the Bass-Quillen conjecture for vector bundles. Read More

2015Jun
Affiliations: 1AIP Potsdam, 2GEPI Meudon, 3Uni Goettingen, 4ESO Garching, 5ESO Garching, 6Uni Goettingen, 7AIP Potsdam, 8ESO Garching, 9AIP Potsdam, 10CRAL Lyon, 11ESO Santiago, 12Leiden Observatory, 13AIP Potsdam, 14AIP Potsdam, 15Leiden Observatory, 16CRAL Lyon, 17CRAL Lyon, 18AIP Potsdam

We present a new integral-field spectroscopic dataset of the central part of the Orion Nebula (M 42), observed with the MUSE instrument at the ESO VLT. We reduced the data with the public MUSE pipeline. The output products are two FITS cubes with a spatial size of ~5. Read More

We establish a general "affine representability" result in ${\mathbb A}^1$-homotopy theory over a general base. We apply this result to obtain representability results for vector bundles in ${\mathbb A}^1$-homotopy theory. Our results simplify and significantly generalize F. Read More

We present some new results on the cohomology of a large scope of SL\_2-groups in degrees above the virtual cohomological dimension; yielding some partial positive results for the Quillen conjecture in rank one. We combine these results with the known partial positive results and the known types of counterexamples to the Quillen conjecture, in order to formulate a refined variant of the conjecture. Read More

2015Feb
Affiliations: 1GEPI, Observatoire de Paris, 2Leibniz-Institut für Astrophysik Potsdam, 3Institut für Physik und Astronomie, Universität Potsdam, 4European Southern Observatory, 5GEPI, Observatoire de Paris, 6Leiden Observatory, Leiden University, 7Institut für Astrophysik, Universität Göttingen, 8Leibniz-Institut für Astrophysik Potsdam

Diffuse Interstellar Bands (DIBs) are non-stellar weak absorption features of unknown origin found in the spectra of stars viewed through one or several clouds of Interstellar Medium (ISM). Research of DIBs outside the Milky Way is currently very limited. Specifically spatially resolved investigations of DIBs outside of the Local Group is, to our knowledge, inexistent. Read More

The note provides a description of the homology of $GL_3$ over function rings of affine elliptic curves over arbitrary fields, following the earlier work of Takahashi and Knudson in the case $GL_2$. Some prospects for applications to K-theory of elliptic curves are also discussed. Read More

This archive summarizes a working paper and conference proceedings related to laser wire scanner development for the Future Linear Collider (FLC) in the years 2001 to 2006. In particular the design, setup and data taking for the laser wire experiments at PETRA II and CT2 are described. The material is focused on the activities undertaken by Royal Holloway University of London (RHUL). Read More

In this paper, we provide number-theoretic formulas for Farrell-Tate cohomology for SL\_2 over rings of S-integers in number fields satisfying a weak regularity assumption. These formulas describe group cohomology above the virtual cohomological dimension, and can be used to study some questions in homology of linear groups. We expose three applications, to (I) detection questions for the Quillen conjecture,(II) the existence of transfers for the Friedlander--Milnor conjecture,(III) cohomology of SL\_2 over number fields. Read More

We study the problem of classifying projectivizations of rank-two vector bundles over ${\mathbb P}^2$ up to various notions of equivalence that arise naturally in ${\mathbb A}^1$-homotopy theory, namely ${\mathbb A}^1$-weak equivalence and ${\mathbb A}^1$-$h$-cobordism. First, we classify such varieties up to ${\mathbb A}^1$-weak equivalence: over algebraically closed fields having characteristic unequal to two the classification can be given in terms of characteristic classes of the underlying vector bundle. When the base field is ${\mathbb C}$, this classification result can be compared to a corresponding topological result and we find that the algebraic and topological homotopy classifications agree. Read More

Large statistical samples of quasar spectra have previously indicated possible cosmological variations in the fine-structure constant, $\alpha$. A smaller sample of higher signal-to-noise ratio spectra, with dedicated calibration, would allow a detailed test of this evidence. Towards that end, we observed equatorial quasar HS 1549$+$1919 with three telescopes: the Very Large Telescope, Keck and, for the first time in such analyses, Subaru. Read More

2014Aug

The Advanced Superconducting Test Accelerator (ASTA) facility is currently under construction at Fermilab. With a 1-ms macropulse composed of up to 3000 micropulses and with beam energies projected from 45 to 800 MeV, the need for non-intercepting diagnostics for beam size, position, energy, and bunch length is clear. In addition to the rf BPMs, optical synchrotron radiation (OSR), and optical diffraction radiation (ODR) techniques already planned, we propose the use of undulator radiation from a dedicated device for diagnostics. Read More

For a variety with a Whitney stratification by affine spaces, we study categories of motivic sheaves which are constant mixed Tate along the strata. We are particularly interested in those cases where the category of mixed Tate motives over a point is equivalent to the category of finite-dimensional bigraded vector spaces. Examples of such situations include rational motives on varieties over finite fields and modules over the spectrum representing the semisimplification of de Rham cohomology for varieties over the complex numbers. Read More

The present paper studies the homology of the groups $SL_2(k[C])$ and $GL_2(k[C])$ where $C=\overline{C}\setminus\{P_1,\dots,P_s\}$ is a smooth affine curve over an algebraically closed field $k$. It is well-known that these groups act on a product of trees and the quotients can be described in terms of certain equivalence classes of vector bundles on the complete curve. There is a natural subcomplex of cells with non-unipotent isotropy group. Read More

This article summarizes the latest results on the proton-to-electron mass ratio $\mu$ derived from H$_2$ observations at high redshift in the light of possible variations of fundamental physical constants. The focus lies on UVES observations of the past years as enormous progress was achieved since the first positive results on $\Delta\mu/\mu$ were published. With the better understanding of systematics, dedicated observation runs, and numerous approaches to improve wavelength calibration accuracy, all current findings are in reasonable good agreement with no variation and provide an upper limit of $\Delta\mu/\mu < 1\times 10^{-5}$ for the redshift range of $2 <$ z $< 3$. Read More

This article summarizes the latest results on the proton-to-electron mass ratio $\mu$ derived from H$_2$ observations at high redshift in the light of possible variations of fundamental physical constants. The focus lies on UVES observations of the past years as enormous progress was achieved since the first positive results on $\Delta\mu/\mu$ were published. With the better understanding of systematics, dedicated observation runs, and numerous approaches to improve wavelength calibration accuracy, all current findings are in reasonable good agreement with no variation and provide an upper limit of $\Delta\mu/\mu$ $< 1\times 10^{-5}$ for the redshift range of $2 <$ z $< 3$. Read More

2013Oct
Affiliations: 1GEPI - Observatoire de Paris, 2IUCAA, 3Centre for Astrophysics and Supercomputing, Swinburne University of Technology, 4Hamburger Sternwarte, 5INAF - OA Trieste, 6INAF - OA Trieste, 7IUCAA, 8Centre for Astrophysics and Supercomputing, Swinburne University of Technology, 9IAP, 10Ioffe Physical-Technical Institute, 11ESO, 12Centre for Astrophysics and Supercomputing, Swinburne University of Technology, 13Ioffe Physical-Technical Institute, 14Departamento de Astronomia, Universidad de Chile, 15Centro de Astrofísica, Universidade do Porto, 16Hamburger Sternwarte, 17INAF - OA Trieste

Absorption-line systems detected in high resolution quasar spectra can be used to compare the value of dimensionless fundamental constants such as the fine-structure constant, alpha, and the proton-to-electron mass ratio, mu = m_p/m_e, as measured in remote regions of the Universe to their value today on Earth. In recent years, some evidence has emerged of small temporal and also spatial variations in alpha on cosmological scales which may reach a fractional level of 10 ppm . We are conducting a Large Programme of observations with VLT UVES to explore these variations. Read More

We present an accurate analysis of the H2 absorption lines from the zabs ~ 2.4018 damped Ly{\alpha} system towards HE 0027-1836 observed with the Very Large Telescope Ultraviolet and Visual Echelle Spectrograph (VLT/UVES) as a part of the European Southern Observatory Large Programme "The UVES large programme for testing fundamental physics" to constrain the variation of proton-to-electron mass ratio, {\mu} = mp/me. We perform cross-correlation analysis between 19 individual exposures taken over three years and the combined spectrum to check the wavelength calibration stability. Read More

The goal of the paper is to achieve - in the special case of the linear group SL_2 - some understanding of the relation between group homology and its A^1-invariant replacement. We discuss some of the general properties of A^1-invariant group homology, such as stabilization sequences and Grothendieck-Witt module structures. Together with very precise knowledge about refined Bloch groups, these methods allow to deduce that in general there is a rather large difference between group homology and its A^1-invariant version. Read More

Absorption line systems detected in quasar spectra can be used to compare the value of the fine-structure constant, {\alpha}, measured today on Earth with its value in distant galaxies. In recent years, some evidence has emerged of small temporal and also spatial variations of {\alpha} on cosmological scales which may reach a fractional level of ~ 10 ppm (parts per million). To test these claims we are conducting a Large Program with the VLT UVES . Read More

In this note, we show that the units in Grothendieck-Witt rings extend to an unramified strictly A^1-invariant sheaf of abelian groups on the category of smooth schemes. This implies that there is an A^1-local classifying space of spherical fibrations. Read More

2013Jan
Affiliations: 1Fermilab, 2Fermilab, 3Fermilab, 4Fermilab, 5Fermilab, 6Fermilab, 7Fermilab, 8Fermilab, 9Fermilab, 10Fermilab, 11Fermilab, 12Fermilab, 13Fermilab, 14Fermilab, 15Fermilab, 16Fermilab, 17Fermilab, 18Fermilab, 19SLAC

The Project X Injector Experiment (PXIE), a test bed for the Project X front end, will be completed at Fermilab at FY12-16. One of the challenging goals of PXIE is demonstration of the capability to form a 1 mA H- beam with an arbitrary selected bunch pattern from the initially 5 mA 162.5 MHz CW train. Read More

2013Jan
Affiliations: 1Fermilab, 2Fermilab, 3Fermilab, 4Fermilab, 5Fermilab, 6Fermilab, 7Fermilab, 8Fermilab, 9Fermilab, 10Fermilab, 11Fermilab, 12Fermilab, 13Fermilab, 14Fermilab, 15Fermilab, 16Fermilab

The Advanced Superconducting Test Acccelerator (ASTA) is being constructed at Fermilab. The existing New Muon Lab (NML) building is being converted for this facility. The accelerator will consist of an electron gun, injector, beam acceleration section consisting of 3 TTF-type or ILC-type cryomodules, multiple downstream beamlines for testing diagnostics and conducting various beam tests, and a high power beam dump. Read More

2013Jan
Affiliations: 1Fermilab, 2Fermilab, 3Fermilab, 4Fermilab, 5Fermilab, 6Fermilab, 7Fermilab

Fermilab is planning the construction of a prototype front end of the Project X linac. The Project X Injector Experiment (PXIE) is expected to accelerate 1 mA cw H- beam up to 30 MeV. Some of the major goals of the project are to test a cw RFQ and H- source, a broadband bunch-by-bunch beam chopper and a low-energy superconducting linac. Read More

2013Jan
Affiliations: 1Fermilab, 2Fermilab, 3Fermilab, 4Fermilab, 5Fermilab, 6Fermilab, 7Fermilab, 8Fermilab, 9SLAC

A capability to provide a large variety of bunch patterns is crucial for the concept of the Project X serving MW-range beam to several experiments simultaneously. This capability will be realized by the Medium Energy Beam Transport's (MEBT) chopping system that will divert 80% of all bunches of the initially 5mA, 2.1 MeV CW 162. Read More

Higher Order Modes (HOM) excited by the beam in the 3.9 GHz accelerating cavities in FLASH can be used for beam position diagnostics, as in a cavity beam position monitor. Previous studies of the modal choices within the complicated spectrum have revealed several options: cavity modes with strong coupling to the beam, and therefore with the potential for better position resolution, but which are propagating within all 4 cavities, and modes localized in the cavities or the beam pipes, which can give localized position information, but which provide worse resolution. Read More

2012Sep
Affiliations: 1Fermilab, 2Fermilab, 3Fermilab, 4Fermilab, 5Fermilab, 6Fermilab, 7Fermilab, 8Fermilab, 9Fermilab, 10Fermilab, 11Fermilab, 12Fermilab, 13Fermilab, 14Fermilab, 15Fermilab, 16Fermilab, 17Fermilab, 18Fermilab, 19Fermilab, 20Fermilab, 21Fermilab, 22Fermilab, 23Fermilab, 24Fermilab, 25Fermilab, 26Fermilab, 27Fermilab

This paper describes the development of a digital-based Beam Position System which was designed, developed, and adapted for the Tevatron during Collider Run II. Read More

The first cryomodule for the beam test facility at the Fermilab New-Muon-Lab building is currently under RF commissioning. Among other diagnostics systems, the transverse position of the helium gas return pipe with the connected 1.3 GHz SRF accelerating cavities is measured along the ~15 m long module using a stretched-wire position monitoring system. Read More

2012Sep
Affiliations: 1Fermilab, 2Fermilab, 3Fermilab, 4Fermilab, 5Fermilab, 6Fermilab, 7Fermilab, 8Fermilab, 9Fermilab, 10Fermilab, 11KEK, Tsukuba, 12KEK, Tsukuba

A beam position monitor (BPM) upgrade at the KEK Accelerator Test Facility (ATF) damping ring has been accomplished, carried out by a KEK/FNAL/SLAC collaboration under the umbrella of the global ILC R&D effort. The upgrade consists of a high resolution, high reproducibility read-out system, based on analog and processing, and also implements a new automatic gain error correction schema. The technical concept and realization as well as results of beam studies are presented. Read More

2012Aug
Affiliations: 1Fermilab, 2Fermilab, 3Fermilab, 4Fermilab, 5Fermilab, 6Fermilab, 7Fermilab, 8Fermilab, 9Fermilab, 10Fermilab

The beam-profile diagnostics station prototype for the superconducting rf electron linac being constructed at Fermilab at the New Muon Lab has been tested. The station uses intercepting radiation converter screens for the low-power beam mode: either a 100-\mu m thick YAG:Ce single crystal scintillator or a 1-\mu m thin Al optical transition radiation (OTR) foil. The screens are oriented with the surface perpendicular to the beam direction. Read More

2012Aug
Affiliations: 1Fermilab, 2Fermilab, 3Fermilab, 4Fermilab, 5Fermilab, 6Fermilab, 7Fermilab, 8Fermilab, 9Fermilab, 10Fermilab, 11Fermilab, 12Fermilab, 13Fermilab, 14Fermilab, 15Fermilab, 16Fermilab

A superconducting RF accelerator test facility is being constructed at Fermilab. The existing New Muon Lab (NML) building is being converted for this facility. The accelerator will consist of an electron gun, injector, beam acceleration section consisting of 3 TTF-type or ILC-type cryomodules, multiple downstream beam lines for testing diagnostics and conducting various beam tests, and a high power beam dump. Read More

Beam-excited higher order modes (HOM) in accelerating cavities contain transverse beam position information. Previous studies have narrowed down three modal options for beam position diagnostics in the third harmonic 3.9 GHz cavities at FLASH. Read More

2012Jul
Affiliations: 1CERN, 2CERN, 3Fermilab, 4Fermilab, 5Fermilab

A common-mode free cavity BPM is currently under development at Fermilab within the ILC-CLIC collaboration. This monitor will be operated in a CLIC Main Linac multi-bunch regime, and needs to provide both, high spatial and time resolution. We present the design concept, numerical analysis, investigation on tolerances and error effects, as well as simulations on the signal response applying a multi-bunch stimulus. Read More

2012Jul
Affiliations: 1CERN, 2CERN, 3CERN, 4Fermilab, 5Fermilab, 6Fermilab, 7Fermilab

In frame of the development of a high resolution BPM system for the CLIC Main Linac we present the design of a cavity BPM prototype. It consists of a waveguide loaded dipole mode resonator and a monopole mode reference cavity, both operating at 15 GHz, to be compatible with the bunch frequencies at the CLIC Test Facility. Requirements, design concept, numerical analysis, and practical considerations are discussed. Read More

For an isotropic reductive group G satisfying a suitable rank condition over an infinite field k, we show that the sections of the $\mathbb{A}^1$-fundamental group sheaf of G over an extension field L/k can be identified with the second group homology of G(L). For a split group G, we provide explicit loops representing all elements in the $\mathbb{A}^1$-fundamental group. Using $\mathbb{A}^1$-homotopy theory, we deduce a Steinberg relation for these explicit loops. Read More

2012Jul
Affiliations: 1Orsay and KEK, Tsukuba, 2Valencia U., IFIC, 3SLAC, 4Daresbury, 5Oxford U., JAI, 6KEK, Tsukuba, 7KEK, Tsukuba, 8Beijing, Inst. High Energy Phys., 9SLAC, 10Oxford U., JAI, 11Royal Holloway, U. of London, 12Savoie U., 13Royal Holloway, U. of London, 14Royal Holloway, U. of London, 15Oxford U., JAI, 16Oxford U., JAI, 17Oxford U., JAI, 18Oxford U., JAI, 19CERN, 20Royal Holloway, U. of London, 21DESY, 22Valencia U., IFIC, 23KEK, Tsukuba, 24Beijing, Inst. High Energy Phys., 25Savoie U., 26Fermilab, 27Ecole Polytechnique, 28KEK, Tsukuba, 29Kyungpook Natl. U., 30KEK, Tsukuba, 31Pohang Accelerator Lab., 32Pohang Accelerator Lab., 33Kyoto U., Inst. Chem. Res., 34Savoie U., 35Daresbury, 36Tokyo U., 37Royal Holloway, U. of London, 38Kyungpook Natl. U., 39Kyungpook Natl. U., 40Pohang Accelerator Lab., 41Tokyo U., 42KEK, Tsukuba, 43KEK, Tsukuba, 44KEK, Tsukuba, 45SLAC, 46University Coll. London, 47KEK, Tsukuba, 48SLAC, 49Royal Holloway, U. of London, 50KEK, Tsukuba, 51Tokyo U., 52SLAC, 53Tohoku U., 54KEK, Tsukuba, 55Tokyo U., 56Pohang Accelerator Lab., 57Brookhaven, 58SLAC, 59Oxford U., JAI, 60SLAC, 61SLAC, 62Orsay and KEK, Tsukuba, 63Oxford U., JAI, 64Orsay, 65Fermilab, 66Tohoku U., 67Manchester U., 68CERN, 69SLAC, 70SLAC, 71Tokyo U., 72KEK, Tsukuba, 73Oxford U., JAI, 74Hiroshima U., 75KEK, Tsukuba, 76KEK, Tsukuba, 77CERN, 78KEK, Tsukuba, 79Oxford U., JAI, 80Ecole Polytechnique, 81SLAC, 82Oxford U., JAI, 83Fermilab, 84SLAC, 85SLAC, 86Liverpool U., 87SLAC, 88Tokyo U., 89Tokyo U., 90SLAC, 91Tokyo U., 92KEK, Tsukuba, 93SLAC, 94CERN

ATF2 is a final-focus test beam line which aims to focus the low emittance beam from the ATF damping ring to a vertical size of about 37 nm and to demonstrate nanometer level beam stability. Several advanced beam diagnostics and feedback tools are used. In December 2008, construction and installation were completed and beam commissioning started, supported by an international team of Asian, European, and U. Read More