Publications related to Spacetime algebra

Geometric Algebra for Optimal Control With Applications in Manipulation Tasks

Many problems in robotics are fundamentally problems of geometry, which have led to an increased research effort in geometric methods for robotics in recent years. The results were algorithms using the various frameworks of screw theory, Lie algebra, and d ...

IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC2023

Experimental Observation and Spin Texture of Dirac Node Arcs in Tetradymite Topological Metals

Emmanouil Frantzeskakis, Ji Dai

We report the observation of a nontrivial spin texture in Dirac node arcs, i.e., novel topological objects formed when Dirac cones of massless particles extend along an open one-dimensional line in momentum space. We find that such states are present in al ...

AMER PHYSICAL SOC2021

Hamiltonian truncation in Anti-de Sitter spacetime

Kamran Salehi Vaziri, João Miguel Augusto Penedones Fernandes, Marco Meineri, Matthijs Jan Hogervorst

Quantum Field Theories (QFTs) in Anti-de Sitter (AdS) spacetime are often strongly coupled when the radius of AdS is large, and few methods are available to study them. In this work, we develop a Hamiltonian truncation method to compute the energy spectrum ...

Springer Nature2021

Interacting Dirac materials

Gabriel Aeppli

We investigate the extent to which the class of Dirac materials in two-dimensions provides general statements about the behavior of both fermionic and bosonic Dirac quasiparticles in the interacting regime. For both quasiparticle types, we find common feat ...

2020

Efficient Multi-dimensional Diracs Estimation with Linear Sample Complexity

Martin Vetterli, Thierry Blu, Hanjie Pan

Estimating Diracs in continuous two or higher dimensions is a fundamental problem in imaging. Previous approaches extended one dimensional methods, like the ones based on finite rate of innovation (FRI) sampling, in a separable manner, e.g., along the hori ...

2018

Poincaré, Scale and Conformal Symmetries : Gauge Perspective and Cosmological Ramifications

Georgios Karananas

Symmetries are omnipresent and play a fundamental role in the description of Nature. Thanks to them, we have at our disposal nontrivial selection rules that dictate how a theory should be constructed. This thesis, which is naturally divided into two parts, ...

EPFL2016

Zoology of condensed matter: framids, ordinary stuff, extra-ordinary stuff

Riccardo Rattazzi

We classify condensed matter systems in terms of the spacetime symmetries they spontaneously break. In particular, we characterize condensed matter itself as any state in a Poincare-invariant theory that spontaneously breaks Lorentz boosts while preserving ...

Springer Nature2015

Manifestation of a Second Dirac Surface State and Bulk Bands in THz Radiation from Topological Insulators

Helmuth Berger, Hua Chen

Topological insulators (TIs) are interesting quantum matters that have a narrow bandgap for bulk and a Dirac-cone-like conducting surface state (SS). The recent discovered second Dirac surface state (SS) and bulk bands (BBs) located similar to 1.5 eV above ...

Nature Publishing Group2015

Ultraviolet completion without symmetry restoration

Solomon G Shamsuddin Osman Endlich

We show that it is not possible to UV complete certain low-energy effective theories with spontaneously broken spacetime symmetries by embedding them into linear sigma models, that is, by adding "radial" modes and restoring the broken symmetries. When such ...

American Physical Society2014

Joint reconstruction of misaligned images from incomplete measurements for cardiac MRI

Pierre Vandergheynst, Gilles Puy, Gabriele Vincenzo Bonanno

We present a novel method for robust reconstruction of the image of a moving object from incomplete linear measurements. We assume that only few measurements of this object can be acquired at different instants and model the correlation between measurement ...

2013

Joint image registration and reconstruction from compressed multi-view measurements

Pierre Vandergheynst, Gilles Puy

We present a method for joint reconstruction of a set of images representing a given scene from few multi-view measurements obtained by compressed sensing. We model the correlation between measurements using global geometric transformations represented by ...

Spie-Int Soc Optical Engineering2013

Scale-Invariant Models of Gravity and Particle Physics and their Cosmological Implications

Daniel Zenhäusern

Currently, the best theoretical description of fundamental matter and its gravitational interaction is given by the Standard Model (SM) of particle physics and Einstein's theory of General Relativity (GR). These theories contain a number of seemingly unrel ...

EPFL2011

Vector Control of Single-Phase Voltage-Source Converters Based on Fictive-Axis Emulation

Alfred Rufer, Behrooz Bahrani, Stephan Kenzelmann

This paper presents an alternative way for the current regulation of single-phase voltage-source dc-ac converters in direct-quadrature (dq) synchronous reference frames. In a dq reference frame, ac (time varying) quantities appear as dc (time invariant) on ...

Institute of Electrical and Electronics Engineers2011

Fast and accurate computation of hyper-singular integrals in Galerkin surface integral equation formulations via the direct evaluation method

Juan Ramon Mosig, Athanasios Polymeridis

Hypersingular 4-D integrals, arising in the Galerkin discretization of surface integral equation formulations, are computed by means of the direct evaluation method. The proposed scheme extends the basic idea of the singularity cancellation methods, usuall ...

Institute of Electrical and Electronics Engineers2011

Dirac Lie Groups, Dirac Homogeneous Spaces and the Theorem of Drinfeld

Madeleine Jotz

The notions of Poisson Lie group and Poisson homogeneous space are extended to the Dirac category. The theorem of Drinfeld on the one-to-one correspondence between Poisson homogeneous spaces of a Poisson Lie group and a special class of Lagrangian subalgeb ...

2011

Variational Principles For Spin Systems And The Kirchhoff Rod

Tudor Ratiu, François Gay-Balmaz

We obtain the affine Euler-Poincare equations by standard Lagrangian reduction and deduce the associated Clebsch-constrained variational principle. These results are illustrated in deriving the equations of motion for continuum spin systems and Kirchhoff's ...

2009

Vector Control of Single-Phase Voltage Source Converters based on Fictive Axis Emulation

Alfred Rufer, Behrooz Bahrani, Stephan Kenzelmann

This paper presents an alternative way for controlling the current of single-phase voltage source dc-ac inverters in a dq synchronous reference frame. In a dq reference frame, ac (time varying) quantities appear as dc (time invariant) quantities allowing t ...

Ieee Service Center, 445 Hoes Lane, Po Box 1331, Piscataway, Nj 08855-1331 Usa2009

Distributed multi-view image coding with learned dictionaries

Pascal Frossard, Ivana Tosic

This paper addresses the problem of distributed image coding in camera neworks. The correlation between multiple images of a scene captured from different viewpoints can be effiiciently modeled by local geometric transforms of prominent images features. Su ...

2009

Multimedia and food chain modelling of toxics for comparative risk and life cycle impact assessment

Ralph Rosenbaum

The overall goal of this dissertation is to contribute to the development of best available practice in environmental multimedia fate and multipathway exposure modelling for human health and ecosystem impacts, addressing several important aspects. Environm ...

EPFL2006

Long-range radiative interaction between semiconductor quantum dots

Vincenzo Savona, Gaetano Parascandolo

We develop a Maxwell-Schrodinger formalism in order to describe the radiative interaction mechanism between semiconductor quantum dots. We solve the Maxwell equations for the electromagnetic field coupled to the polarization field of a quantum dot ensemble ...

2005