S. Palmer

S. Palmer
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High Energy Physics - Phenomenology (7)
 
Mathematical Physics (7)
 
Mathematics - Mathematical Physics (7)
 
High Energy Physics - Theory (7)
 
Quantitative Biology - Neurons and Cognition (5)
 
High Energy Physics - Experiment (5)
 
Physics - Strongly Correlated Electrons (1)
 
Quantitative Biology - Quantitative Methods (1)

Publications Authored By S. Palmer

Almost all neural computations involve making predictions. Whether an organism is trying to catch prey, avoid predators, or simply move through a complex environment, the data it collects through its senses can guide its actions only to the extent that it can extract from these data information about the future state of the world. An essential aspect of the problem in all these forms is that not all features of the past carry predictive power. Read More

In this thesis, the emerging field of higher gauge theory will be discussed, particularly in relation to problems arising in M-theory, such as selfdual strings and the so-called (2,0) theory. This thesis will begin with a Nahm-like construction for selfdual strings using loop space, the space of loops on spacetime. This construction maps solutions of the Basu-Harvey equation, the BPS equation arising in the description of multiple M2-branes, to solutions of a selfdual string equation on loop space. Read More

VBFNLO is a flexible parton level Monte Carlo program for the simulation of vector boson fusion (VBF), double and triple vector boson (plus jet) production as well as QCD-induced single and double vector boson production plus two jets in hadronic collisions at next-to-leading order (NLO) in the strong coupling constant. Furthermore, Higgs boson plus two jet production via gluon fusion at the one-loop level is included. This note briefly describes the main additional features and processes that have been added in the new release -- VBFNLO Version 2. Read More

Practice of a complex motor gesture involves exploration of motor space to attain a better match to target output, but little is known about the neural code for such exploration. Here, we examine spiking in an area of the songbird brain known to contribute to modification of song output. We find that neurons in the outflow nucleus of a specialized basal ganglia- thalamocortical circuit, the lateral magnocellular nucleus of the anterior nidopallium (LMAN), code for time in the motor gesture (song) both during singing directed to a female bird (performance) and when the bird sings alone (practice). Read More

We present a design and implementation of the Thomas algorithm optimized for hardware acceleration on an FPGA, the Thomas Core. The hardware-based algorithm combined with the custom data flow and low level parallelism available in an FPGA reduces the overall complexity from 8N down to 5N serial arithmetic operations, and almost halves the overall latency by parallelizing the two costly divisions. Combining this with a data streaming interface, we reduce memory overheads to 2 N-length vectors per N-tridiagonal system to be solved. Read More

We present and discuss explicit solutions to the non-abelian self-dual string equation as well as to the non-abelian self-duality equation in six dimensions. These solutions are generalizations of the 't Hooft-Polyakov monopole and the BPST instanton to higher gauge theory. We expect that these solutions are relevant to the effective description of M2- and M5-branes. Read More

M2-branes couple to a 3-form potential, which suggests that their description involves a non-abelian 2-gerbe or, equivalently, a principal 3-bundle. We show that current M2-brane models fit this expectation: they can be reformulated as higher gauge theories on such categorified bundles. We thus add to the still very sparse list of physically interesting higher gauge theories. Read More

We analyze the gauge structure of a recently proposed superconformal field theory in six dimensions. We find that this structure amounts to a weak Courant-Dorfman algebra, which, in turn, can be interpreted as a strong homotopy Lie algebra. This suggests that the superconformal field theory is closely related to higher gauge theory, describing the parallel transport of extended objects. Read More

Guiding behavior requires the brain to make predictions about future sensory inputs. Here we show that efficient predictive computation starts at the earliest stages of the visual system. We estimate how much information groups of retinal ganglion cells carry about the future state of their visual inputs, and show that every cell we can observe participates in a group of cells for which this predictive information is close to the physical limit set by the statistical structure of the inputs themselves. Read More

Redundancies and correlations in the responses of sensory neurons seem to waste neural resources but can carry cues about structured stimuli and may help the brain to correct for response errors. To assess how the retina negotiates this tradeoff, we measured simultaneous responses from populations of ganglion cells presented with natural and artificial stimuli that varied greatly in correlation structure. We found that pairwise correlations in the retinal output remained similar across stimuli with widely different spatio-temporal correlations including white noise and natural movies. Read More

In this paper we discuss the production of a heavy scalar MSSM Higgs boson H and its subsequent decays into pairs of electroweak gauge bosons WW and ZZ. We perform a scan over the relevant MSSM parameters, using constraints from direct Higgs searches and several low-energy observables. We then compare the possible size of the pp -> H -> WW,ZZ cross sections with corresponding Standard Model cross sections. Read More

Vbfnlo is a flexible parton level Monte Carlo program for the simulation of vector boson fusion (VBF), double and triple vector boson (plus jet) production in hadronic collisions at next-to-leading order (NLO) in the strong coupling constant, as well as Higgs boson plus two jet production via gluon fusion at the one-loop level. This note briefly describes the main additional features and processes that have been added in the new release -- Vbfnlo Version 2.6. Read More

Recently a Nahm transform has been discovered for magnetic bags, which are conjectured to arise in the large n limit of magnetic monopoles with charge n. We interpret these ideas using string theory and present some partial proofs of this conjecture. We then extend the notion of bags and their Nahm transform to higher gauge theories and arbitrary domains. Read More

We make the observation that M-brane models defined in terms of 3-algebras can be interpreted as higher gauge theories involving Lie 2-groups. Such gauge theories arise in particular in the description of non-abelian gerbes. This observation allows us to put M2- and M5-brane models on equal footing, at least as far as the gauge structure is concerned. Read More

2012Jan
Authors: LHC Higgs Cross Section Working Group, S. Dittmaier1, C. Mariotti2, G. Passarino3, R. Tanaka4, S. Alekhin, J. Alwall, E. A. Bagnaschi, A. Banfi, J. Blumlein, S. Bolognesi, N. Chanon, T. Cheng, L. Cieri, A. M. Cooper-Sarkar, M. Cutajar, S. Dawson, G. Davies, N. De Filippis, G. Degrassi, A. Denner, D. D'Enterria, S. Diglio, B. Di Micco, R. Di Nardo, R. K. Ellis, A. Farilla, S. Farrington, M. Felcini, G. Ferrera, M. Flechl, D. de Florian, S. Forte, S. Ganjour, M. V. Garzelli, S. Gascon-Shotkin, S. Glazov, S. Goria, M. Grazzini, J. -Ph. Guillet, C. Hackstein, K. Hamilton, R. Harlander, M. Hauru, S. Heinemeyer, S. Hoche, J. Huston, C. Jackson, P. Jimenez-Delgado, M. D. Jorgensen, M. Kado, S. Kallweit, A. Kardos, N. Kauer, H. Kim, M. Kovac, M. Kramer, F. Krauss, C. -M. Kuo, S. Lehti, Q. Li, N. Lorenzo, F. Maltoni, B. Mellado, S. O. Moch, A. Muck, M. Muhlleitner, P. Nadolsky, P. Nason, C. Neu, A. Nikitenko, C. Oleari, J. Olsen, S. Palmer, S. Paganis, C. G. Papadopoulos, T . C. Petersen, F. Petriello, F. Petrucci, G. Piacquadio, E. Pilon, C. T. Potter, J. Price, I. Puljak, W. Quayle, V. Radescu, D. Rebuzzi, L. Reina, J. Rojo, D. Rosco, G. P. Salam, A. Sapronov, J. Schaarschmidt, M. Schonherr, M. Schumacher, F. Siegert, P. Slavich, M. Spira, I. W. Stewart, W. J. Stirling, F. Stockli, C. Sturm, F. J. Tackmann, R. S. Thorne, D. Tommasini, P. Torrielli, F. Tramontano, Z. Trocsanyi, M. Ubiali, S. Uccirati, M. Vazquez Acosta, T. Vickey, A. Vicini, W. J. Waalewijn, D. Wackeroth, M. Warsinsky, M. Weber, M. Wiesemann, G. Weiglein, J. Yu, G. Zanderighi
Affiliations: 1eds., 2eds., 3eds., 4eds.

This Report summarises the results of the second year's activities of the LHC Higgs Cross Section Working Group. The main goal of the working group was to present the state of the art of Higgs Physics at the LHC, integrating all new results that have appeared in the last few years. The first working group report Handbook of LHC Higgs Cross Sections: 1. Read More

VBFNLO is a flexible parton level Monte Carlo program for the simulation of vector boson fusion (VBF), QCD induced single and double vector boson production plus two jets, and double and triple vector boson production (plus jet) in hadronic collisions at next-to-leading order (NLO) in the strong coupling constant, as well as Higgs boson plus two jet production via gluon fusion at the one-loop level. For the new version -- Version 2.7. Read More

We generalize a recently developed ADHMN-like construction of self-dual string solitons using loop space. In particular, we present two extensions: The first one starts from solutions to the Basu-Harvey equation for the ABJM model, the second one starts from solutions to a corresponding BPS equation in an N=2 supersymmetric deformation of the BLG model. Both constructions yield solutions to the abelian and the nonabelian self-dual string equation transgressed to loop space. Read More

Weak boson fusion is expected to be an important Higgs production channel at the LHC. Complete one-loop results for weak boson fusion in the Standard Model have been obtained by calculating the full virtual electroweak corrections and photon radiation and implementing these results into the public Monte Carlo program VBFNLO which includes the NLO QCD corrections. Furthermore the dominant supersymmetric one-loop corrections to neutral Higgs production, in the general case where the MSSM includes complex phases, have been calculated. Read More

To evaluate the nature of the neural code in the cerebral cortex, we have used a combination of theory and experiment to assess how information is represented in a realistic cortical population response. We have shown how a sensory stimulus could be estimated on a biologically-realistic time scale, given brief individual responses from a population of neurons with similar response properties. For neurons in extrastriate motion area MT, a combinatorial code, one that keeps track of the cell identity of action potentials and silences in individual neurons across the population, carries twice as much information about visual motion as does spike count averaged over the same group of cells. Read More

We present the results of an exact diagonalization study of the spin-1/2 Heisenberg antiferromagnet on a two-dimensional version of the pyrochlore lattice, also known as the square lattice with crossings or the checkerboard lattice. Examining the low energy spectra for systems of up to 24 spins, we find that all clusters studied have non-degenerate ground states with total spin zero, and big energy gaps to states with higher total spin. We also find a large number of non-magnetic excitations at energies within this spin gap. Read More

We study the classical Heisenberg model for spins on a pyrochlore lattice interacting via long range dipole-dipole forces and nearest neighbor exchange. Antiferromagnetic exchange alone is known not to induce ordering in this system. We analyze low temperature order resulting from the combined interactions, both by using a mean-field approach and by examining the energy cost of fluctuations about an ordered state. Read More

The first direct experimental evidence for the Fermi surface (FS) driving the helical antiferromagnetic ordering in a gadolinium-yttrium alloy is reported. The presence of a FS sheet capable of nesting is revealed, and the nesting vector associated with the sheet is found to be in excellent agreement with the periodicity of the helical ordering. Read More