32 research outputs found
The Virtue of Defects in 4D Gauge Theories and 2D CFTs
We advance a correspondence between the topological defect operators in
Liouville and Toda conformal field theories - which we construct - and loop
operators and domain wall operators in four dimensional N=2 supersymmetric
gauge theories on S^4. Our computation of the correlation functions in
Liouville/Toda theory in the presence of topological defect operators, which
are supported on curves on the Riemann surface, yields the exact answer for the
partition function of four dimensional gauge theories in the presence of
various walls and loop operators; results which we can quantitatively
substantiate with an independent gauge theory analysis. As an interesting
outcome of this work for two dimensional conformal field theories, we prove
that topological defect operators and the Verlinde loop operators are different
descriptions of the same operators.Comment: 59 pages, latex; v2 corrections to some formula
't Hooft Operators in Gauge Theory from Toda CFT
We construct loop operators in two dimensional Toda CFT and calculate with
them the exact expectation value of certain supersymmetric 't Hooft and dyonic
loop operators in four dimensional \Ncal=2 gauge theories with SU(N) gauge
group. Explicit formulae for 't Hooft and dyonic operators in \Ncal=2^* and
\Ncal=2 conformal SQCD with SU(N) gauge group are presented. We also briefly
speculate on the Toda CFT realization of arbitrary loop operators in these
gauge theories in terms of topological web operators in Toda CFT.Comment: 49 pages, LaTeX. Typos fixed, references adde
When Right Feels Left: Referral of Touch and Ownership between the Hands
Feeling touch on a body part is paradigmatically considered to require stimulation of tactile afferents from the body part in question, at least in healthy non-synaesthetic individuals. In contrast to this view, we report a perceptual illusion where people experience “phantom touches” on a right rubber hand when they see it brushed simultaneously with brushes applied to their left hand. Such illusory duplication and transfer of touch from the left to the right hand was only elicited when a homologous (i.e., left and right) pair of hands was brushed in synchrony for an extended period of time. This stimulation caused the majority of our participants to perceive the right rubber hand as their own and to sense two distinct touches – one located on the right rubber hand and the other on their left (stimulated) hand. This effect was supported by quantitative subjective reports in the form of questionnaires, behavioral data from a task in which participants pointed to the felt location of their right hand, and physiological evidence obtained by skin conductance responses when threatening the model hand. Our findings suggest that visual information augments subthreshold somatosensory responses in the ipsilateral hemisphere, thus producing a tactile experience from the non-stimulated body part. This finding is important because it reveals a new bilateral multisensory mechanism for tactile perception and limb ownership
Mapping the Conformational Dynamics and Pathways of Spontaneous Steric Zipper Peptide Oligomerization
The process of protein misfolding and self-assembly into various, polymorphic aggregates is associated with a number of important neurodegenerative diseases. Only recently, crystal structures of several short peptides have provided detailed structural insights into -sheet rich aggregates, known as amyloid fibrils. Knowledge about early events of the formation and interconversion of small oligomeric states, an inevitable step in the cascade of peptide self-assembly, however, remains still limited
A new era for understanding amyloid structures and disease
The aggregation of proteins into amyloid fibrils and their deposition into plaques and intracellular inclusions is the hallmark of amyloid disease. The accumulation and deposition of amyloid fibrils, collectively known as amyloidosis, is associated with many pathological conditions that can be associated with ageing, such as Alzheimer disease, Parkinson disease, type II diabetes and dialysis-related amyloidosis. However, elucidation of the atomic structure of amyloid fibrils formed from their intact protein precursors and how fibril formation relates to disease has remained elusive. Recent advances in structural biology techniques, including cryo-electron microscopy and solid-state NMR spectroscopy, have finally broken this impasse. The first near-atomic-resolution structures of amyloid fibrils formed in vitro, seeded from plaque material and analysed directly ex vivo are now available. The results reveal cross-β structures that are far more intricate than anticipated. Here, we describe these structures, highlighting their similarities and differences, and the basis for their toxicity. We discuss how amyloid structure may affect the ability of fibrils to spread to different sites in the cell and between organisms in a prion-like manner, along with their roles in disease. These molecular insights will aid in understanding the development and spread of amyloid diseases and are inspiring new strategies for therapeutic intervention