3,415 research outputs found
Gravitational Radiation from Color-Kinematics Duality
We perturbatively calculate classical radiation in Yang-Mills theory and
dilaton gravity, to next-to-leading order in couplings. The radiation is
sourced by the scattering of two relativistic massive scalar sources with the
dynamical effect taken into account, corresponding to the post-Minkowskian
regime in gravity. We show how to arrange the Yang-Mills radiation such that
the duality between colors and kinematics is manifest, including the three-term
Jacobi identity. The search for duality-satisfying expressions exploits an
auxiliary bi-adjoint scalar theory as a guide for locality. The double copy is
obtained by replacing the color factors in Yang-Mills with kinematic
counterparts, following Bern-Carrasco-Johansson construction in S- matrix. On
the gravity side, the radiation is directly computed at the third
post-Minkowskian order with massive sources. We find perfect agreement between
observables in dilaton gravity and the Yang-Mills double copy. This
non-trivially generalizes the leading-order rules by Goldberger and Ridgway.
For the first time, the kinematic Jacobi identity appears beyond field-theory
S-matrix, suggesting that the color-kinematics duality holds more generally.
Our results offer a path for simplifying analytical calculations in
post-Minkowskian regime.Comment: 3 figures, 3 tables, and 7 ancillary files; comments are welcomed;
v2: references added, typos fixed, one more figure is include
Non-renormalization Theorems without Supersymmetry
We derive a new class of one-loop non-renormalization theorems that strongly
constrain the running of higher dimension operators in a general
four-dimensional quantum field theory. Our logic follows from unitarity: cuts
of one-loop amplitudes are products of tree amplitudes, so if the latter vanish
then so too will the associated divergences. Finiteness is then ensured by
simple selection rules that zero out tree amplitudes for certain helicity
configurations. For each operator we define holomorphic and anti-holomorphic
weights, , where and are the number and
sum over helicities of the particles created by that operator. We argue that an
operator can only be renormalized by an operator if
and , absent non-holomorphic
Yukawa couplings. These results explain and generalize the surprising
cancellations discovered in the renormalization of dimension six operators in
the standard model. Since our claims rely on unitarity and helicity rather than
an explicit symmetry, they apply quite generally.Comment: 6 pages, 2 figures, and 2 table
Symmetry and Action for Flavor-Kinematics Duality
We propose a new representation of the nonlinear sigma model that exhibits a
manifest duality between flavor and kinematics. The fields couple exclusively
through cubic Feynman vertices which also serve as the structure constants of
an underlying kinematic algebra. The action is invariant under a combination of
internal and spacetime symmetries whose conservation equations imply
flavor-kinematics duality, ensuring that all Feynman diagrams satisfy kinematic
Jacobi identities. Substituting flavor for kinematics, we derive a new cubic
action for the special Galileon theory. In this picture, the vanishing soft
behavior of amplitudes is a byproduct of the Weinberg soft theorem.Comment: 5 pages+refs; matched to published versio
Simple Recursion Relations for General Field Theories
On-shell methods offer an alternative definition of quantum field theory at
tree-level, replacing Feynman diagrams with recursion relations and interaction
vertices with a handful of seed scattering amplitudes. In this paper we
determine the simplest recursion relations needed to construct a general
four-dimensional quantum field theory of massless particles. For this purpose
we define a covering space of recursion relations which naturally generalizes
all existing constructions, including those of BCFW and Risager. The validity
of each recursion relation hinges on the large momentum behavior of an n-point
scattering amplitude under an m-line momentum shift, which we determine solely
from dimensional analysis, Lorentz invariance, and locality. We show that all
amplitudes in a renormalizable theory are 5-line constructible. Amplitudes are
3-line constructible if an external particle carries spin or if the scalars in
the theory carry equal charge under a global or gauge symmetry. Remarkably,
this implies the 3-line constructibility of all gauge theories with fermions
and complex scalars in arbitrary representations, all supersymmetric theories,
and the standard model. Moreover, all amplitudes in non-renormalizable theories
without derivative interactions are constructible; with derivative
interactions, a subset of amplitudes is constructible. We illustrate our
results with examples from both renormalizable and non-renormalizable theories.
Our study demonstrates both the power and limitations of recursion relations as
a self-contained formulation of quantum field theory.Comment: 27 pages and 2 figures; v2: typos corrected to match journal versio
Hidden Conformal Invariance of Scalar Effective Field Theories
We argue that conformal invariance is a common thread linking several scalar
effective field theories that appear in the double copy and scattering
equations. For a derivatively coupled scalar with a quartic
vertex, classical conformal invariance dictates an infinite tower of additional
interactions that coincide exactly with Dirac-Born-Infeld theory analytically
continued to spacetime dimension . For the case of a quartic vertex, classical conformal invariance constrains the theory to be the
special Galileon in dimensions. We also verify the conformal invariance
of these theories by showing that their amplitudes are uniquely fixed by the
conformal Ward identities. In these theories, conformal invariance is a much
more stringent constraint than scale invariance.Comment: 7 page
Language Transfer of Audio Word2Vec: Learning Audio Segment Representations without Target Language Data
Audio Word2Vec offers vector representations of fixed dimensionality for
variable-length audio segments using Sequence-to-sequence Autoencoder (SA).
These vector representations are shown to describe the sequential phonetic
structures of the audio segments to a good degree, with real world applications
such as query-by-example Spoken Term Detection (STD). This paper examines the
capability of language transfer of Audio Word2Vec. We train SA from one
language (source language) and use it to extract the vector representation of
the audio segments of another language (target language). We found that SA can
still catch phonetic structure from the audio segments of the target language
if the source and target languages are similar. In query-by-example STD, we
obtain the vector representations from the SA learned from a large amount of
source language data, and found them surpass the representations from naive
encoder and SA directly learned from a small amount of target language data.
The result shows that it is possible to learn Audio Word2Vec model from
high-resource languages and use it on low-resource languages. This further
expands the usability of Audio Word2Vec.Comment: arXiv admin note: text overlap with arXiv:1603.0098
Leading Effect of CP Violation with Four Generations
In the Standard Model with a fourth generation of quarks, we study the
relation between the Jarlskog invariants and the triangle areas in the 4-by-4
CKM matrix. To identify the leading effects that may probe the CP violation in
processes involving quarks, we invoke small mass and small angle expansions,
and show that these leading effects are enhanced considerably compared to the
three generation case by the large masses of fourth generation quarks. We
discuss the leading effect in several cases, in particular the possibility of
large CP violation in processes, which echoes the heightened recent
interest because of experimental hints.Comment: 12 pages, no figur
Nanodiscs via interfacial cross-linking of smectic liquid-crystalline phase and their application
Triallyl(3,4,5- tridodecyloxybenzyl)ammonium bromide was used to form lyotropic liquid crystal. Inverted hexagonal phase was the original target. The liquid crystal and the cross-linked material were characterized by XRD (powder x-ray diffraction), PLM (polarized light microscopy), TEM (transmission electron microscopy), and AFM (atomic force microscopy). The characterizations indicated that the surfactant did not form inverse hexagonal phase but smectic phase instead. The cross-linking afforded nanodisc-like structures as a result.
The large size of the triallyl ammonium headgroup was possibly responsible for the phase change
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