Jekyll2022-01-28T23:09:32+00:00http://amplitudes.org/feed.xmlAmplitudes.orgComing soon.John Joseph M. CarrascoAmplitudes and Insights Group at Northwestern University2022-01-27T00:00:00+00:002022-01-27T00:00:00+00:00http://amplitudes.org/jobs/Northwestern<h1 id="postdoctoral-position-in-theoretical-high-energy-physics">Postdoctoral Position in Theoretical High Energy Physics</h1>
<p>The <a href="http://fancyphysics.org">Amplitudes and Insights group</a> in the Department of Physics and Astronomy of Weinberg College of Arts and Sciences at Northwestern University welcomes applications for a postdoctoral research scholar to join the group beginning the autumn of 2021 with a focus on large-scale analytic prediction.</p>
<p>The posting shall remain open until the position is filled, however for full consideration, please apply by close of business on February 15, 2022.</p>
<p>What you will do:</p>
<ol>
<li>Apply amplitude insights to physical stories from particle physics, to gravitational wave physics, to cosmology.</li>
<li>Discover new structure in multi-loop gauge and gravity invariant predictions.</li>
<li>Provide technical leadership in large-scale analytic calculation, mentoring and supporting other members of the group.</li>
</ol>
<p>Required Qualifications: PhD in physics. Penchant for gauge invariance.</p>
<p>Highly Desired:</p>
<ul>
<li>Experience in calculating and analyzing the UV properties of multi-loop gauge and gravity scattering amplitudes, and associated automation.</li>
<li>Experience constructing representations manifesting the duality between color and kinematics in non-trivial gauge theories and double-copy construction in the color-dual web of theories.</li>
<li>Experience with the low-energy expansion of string predictions at tree and loop level.</li>
<li>Experience with classical gravitational wave calculation at higher order either in PN or PM expansions, preferably both.</li>
<li>Experience with scientific computing towards analytic results on high performance computing clusters.</li>
</ul>
<p>To Apply: Applicants should send a CV with a list of publications and contact information for three references, as well as a scientific research statement of no greater than 4 pages, to <a href="mailto:carrasco@northwestern.edu">John Joseph Carrasco</a>.</p>
<p><em>Northwestern University is an Equal Opportunity, Affirmative Action Employer of all protected classes, including veterans and individuals with disabilities. Women, underrepresented racial and ethnic minorities, individuals with disabilities, and veterans are encouraged to apply. Hiring is contingent upon eligibility to work in the United States.</em></p>John Joseph M. CarrascoPostdoc in hep-thRadiated momentum in the Post-Minkowskian worldline approach via reverse unitarity2021-10-19T00:00:00+00:002021-10-19T00:00:00+00:00http://amplitudes.org/amplitudes/2110_10140<h1 id="links">Link(s):</h1>
<p>Paper and ancilary files.</p>
<ul>
<li><a href="https://arxiv.org/abs/2110.10140">Radiated momentum in the Post-Minkowskian worldline approach via reverse unitarity</a></li>
<li><a href="https://arxiv.org/src/2110.10140/anc">ancilary files</a></li>
</ul>
<h1 id="authors">Author(s):</h1>
<p>Massimiliano Maria Riva, Filippo Vernizzi</p>
<h1 id="abstract">Abstract:</h1>
<p>We compute the four-momentum radiated during the scattering of two spinless bodies, at leading order in the Newton’s contant $G$ and at all orders in the velocities, using the Effective Field Theory worldline approach. Following \cite{Mougiakakos:2021ckm}, we derive the conserved stress-energy tensor linearly coupled to gravity generated by localized sources, at leading and next-to-leading order in $G$, and from that the classical probability amplitude of graviton emission. The total emitted momentum is obtained by phase-space integration of the graviton momentum weighted by the modulo squared of the radiation amplitude. We recast this as a two-loop integral that we solve using techniques borrowed from particle physics, such as reverse unitarity, reduction to master integrals by integration-by-parts identities and canonical differential equations. The emitted momentum agrees with recent results obtained by other methods. Our approach provides an alternative way of directly computing radiated observables in the post-Minkowskian expansion without going through the classical limit of scattering amplitudes.</p>John Joseph M. Carrascohttp://prettyquestions.comPaper and ancillary files.Singularities of eight- and nine-particle amplitudes from cluster algebras and tropical geometry2021-10-12T00:00:00+00:002021-10-12T00:00:00+00:00http://amplitudes.org/amplitudes/2106_01392<h1 id="links">Link(s):</h1>
<p>Paper and ancilary files.</p>
<ul>
<li><a href="https://arxiv.org/abs/2106.01392">Singularities of eight- and nine-particle amplitudes from cluster algebras and tropical geometry</a></li>
<li><a href="https://arxiv.org/src/2106.01392/anc">ancilary files</a></li>
</ul>
<h1 id="authors">Author(s):</h1>
<p>Niklas Henke, Georgios Papathanasiou</p>
<h1 id="abstract">Abstract:</h1>
<p>We further exploit the relation between tropical Grassmannians and $\operatorname{Gr}(4,n)$ cluster algebras in order to make and refine predictions for the singularities of scattering amplitudes in $\mathcal{N}=4$ planar super Yang-Mills theory at higher multiplicity $n\ge 8$. As a mathematical foundation that provides access to square-root symbol letters in principle for any $n$, we analyse infinite mutation sequences in cluster algebras with general coefficients. First specialising our analysis to the eight-particle amplitude, and comparing it with a recent, closely related approach based on scattering diagrams, we find that the only additional letters the latter provides are the two square roots associated to the four-mass box. In combination with a tropical rule for selecting a finite subset of variables of the infinite $\operatorname{Gr}(4,9)$ cluster algebra, we then apply our results to obtain a collection of $3,078$ rational and $2,349$ square-root letters expected to appear in the nine-particle amplitude. In particular these contain the alphabet found in an explicit 2-loop NMHV symbol calculation at this multiplicity.</p>John Joseph M. Carrascohttp://prettyquestions.comPaper and ancillary files.The $ppto W(to lν)+γ$ process at next-to-next-to-leading order2021-09-14T00:00:00+00:002021-09-14T00:00:00+00:00http://amplitudes.org/amplitudes/2105_00954<h1 id="links">Link(s):</h1>
<p>Paper and ancilary files.</p>
<ul>
<li><a href="https://arxiv.org/abs/2105.00954">The $ppto W(to lν)+γ$ process at next-to-next-to-leading order</a></li>
<li><a href="https://arxiv.org/src/2105.00954/anc">ancilary files</a></li>
</ul>
<h1 id="authors">Author(s):</h1>
<p>John M. Campbell, Giuseppe De Laurentis, R. Keith Ellis, Satyajit Seth</p>
<h1 id="abstract">Abstract:</h1>
<p>We present details of the calculation of the $pp\to W(\to l\nu) \gamma$ process at next-to-next-to-leading order in QCD, calculated using the jettiness slicing method. The calculation is based entirely on analytic amplitudes. Because of the radiation zero, the NLO QCD contribution from the $gq$ channel is as important as the contribution from the Born $q\bar{q}$ process, disrupting the normal counting of leading and sub-leading contributions. We also assess the importance of electroweak (EW) corrections, including the EW corrections to both the six-parton channel $0\to \bar{u} d \nu e^+\gamma g$ and the five-parton channel $0\to \bar{u} d \nu e^+ \gamma$. Previous experimental results have been shown to agree with theoretical predictions, taking into account the large experimental errors. With the advent of run II data from the LHC, the statistical errors on the data will decrease, and will be competitive with the error on theoretical predictions for the first time. We present numerical results for $\sqrt{s}=7$ and 13 TeV. Analytic results for the one-loop six-parton QCD amplitude and the tree-level seven-parton QCD amplitude are presented in appendices.</p>John Joseph M. Carrascohttp://prettyquestions.comPaper and ancillary files.SUSY in the Sky with Gravitons2021-09-09T00:00:00+00:002021-09-09T00:00:00+00:00http://amplitudes.org/amplitudes/2109_04465<h1 id="links">Link(s):</h1>
<p>Paper and ancilary files.</p>
<ul>
<li><a href="https://arxiv.org/abs/2109.04465">SUSY in the Sky with Gravitons</a></li>
<li><a href="https://arxiv.org/src/2109.04465/anc">ancilary files</a></li>
</ul>
<h1 id="authors">Author(s):</h1>
<p>Gustav Uhre Jakobsen, Gustav Mogull, Jan Plefka, Jan Steinhoff</p>
<h1 id="abstract">Abstract:</h1>
<p>Picture yourself in the wave zone of a gravitational scattering event of two massive, spinning compact bodies (black holes, neutron stars or stars). We show that this system of genuine astrophysical interest enjoys a hidden $\mathcal{N}=2$ supersymmetry, at least to the order of spin-squared (quadrupole) interactions in arbitrary $D$ spacetime dimensions. Using the ${\mathcal N}=2$ supersymmetric worldline action, augmented by finite-size corrections for the non-Kerr black hole case, we build a quadratic-in-spin extension to the worldline quantum field theory (WQFT) formalism introduced in our previous work, and calculate the two bodies’ deflection and spin kick to sub-leading order in the post-Minkowskian expansion in Newton’s constant $G$. For spins aligned to the normal vector of the scattering plane we also obtain the scattering angle. All $D$-dimensional observables are derived from an eikonal phase given as the free energy of the WQFT, that is invariant under the $\mathcal{N}=2$ supersymmetry transformations.</p>John Joseph M. Carrascohttp://prettyquestions.comPaper and ancillary files.Standard Model EFTs via On-Shell Methods2021-08-23T00:00:00+00:002021-08-23T00:00:00+00:00http://amplitudes.org/amplitudes/2108_03669<h1 id="links">Link(s):</h1>
<p>Paper and ancilary files.</p>
<ul>
<li><a href="https://arxiv.org/abs/2108.03669">Standard Model EFTs via On-Shell Methods</a></li>
<li><a href="https://arxiv.org/src/2108.03669/anc">ancilary files</a></li>
</ul>
<h1 id="authors">Author(s):</h1>
<p>Manuel Accettulli Huber, Stefano De Angelis</p>
<h1 id="abstract">Abstract:</h1>
<p>We present the Standard Model Effective Field Theories (SMEFT) from purely on-shell arguments. Starting from few basics assumptions such as Poincar'e invariance and locality, we classify all the renormalisable and non-renormalisable interactions at lowest order in the couplings. From these building blocks, we review how locality and unitarity enforce Lie algebra structures to appear in the S-matrix elements together with relations among couplings (and hypercharges). Furthermore, we give a fully on-shell algorithm to compute any higher-point tree-level amplitude (or form factor) in generic EFTs, bypassing BCFW-like recursion relations which are known to be problematic when non-renormalisable interactions are involved. Finally, using known amplitudes techniques we compute the mixing matrix of SMEFT marginal interactions up to mass dimension 8, to linear order in the effective interactions.</p>John Joseph M. Carrascohttp://prettyquestions.comPaper and ancillary files.Extracting Einstein from the Loop-Level Double-Copy2021-08-15T00:00:00+00:002021-08-15T00:00:00+00:00http://amplitudes.org/integrands/2108_06798<h1 id="links">Link(s):</h1>
<p>Paper and ancilary files.</p>
<ul>
<li><a href="https://arxiv.org/abs/2108.06798">Extracting Einstein from the Loop-Level Double-Copy</a></li>
<li><a href="https://arxiv.org/src/2108.06798/anc">ancilary files</a></li>
</ul>
<h1 id="authors">Author(s):</h1>
<p>John Joseph M. Carrasco, Ingrid A. Vazquez-Holm</p>
<h1 id="abstract">Abstract:</h1>
<p>The naive double-copy of (multi) loop amplitudes involving massive matter coupled to gauge theories will generically produce amplitudes in a gravitational theory that contains additional contributions from propagating antisymmetric tensor and dilaton states even at tree-level. We present a graph-based approach that combines the method of maximal cuts with double-copy construction to offer a systematic framework to isolate the pure Einstein-Hilbert gravitational contributions through loop level. Indeed this allows for a bootstrap of pure-gravitational results from the double-copy of massive scalar-QCD. We apply this to construct the novel result of the D-dimensional one-loop five-point QFT integrand relevant in the classical limit to generating observables associated with the radiative effects of massive black-hole scattering via pure Einstein-Hilbert gravity.</p>John Joseph M. Carrascohttp://prettyquestions.comPaper and ancillary files.SAGEX 2021 PhD Organized Summer School2021-08-13T00:00:00+00:002021-08-13T00:00:00+00:00http://amplitudes.org/lectures/SAGEX_PhD_School<h1 id="link">Link</h1>
<p>Lecture Series: SAGEX PhD School in Amplitudes, 2021,
<a href="https://www.youtube.com/playlist?list=PLC6RXWfJfoYw0zStFGyxxbiXuO7sqD86U">here</a>.</p>
<h1 id="lecturer">Lecturer</h1>
<p>Thomasz Lukowski, Sabrina Pasterski, Chia-Hsien Shen, Kai Yan</p>
<h1 id="description">Description</h1>
<p>Recording of scientific lectures relevant to the area of quantum scattering amplitudes in theoretical physics. Lectures were given online at the SAGEX PhD School in Amplitudes, from August 9-13 2021.</p>John Joseph M. Carrascohttp://prettyquestions.comLinks to VideoAnalytic results for two-loop planar master integrals for Bhabha scattering2021-08-09T00:00:00+00:002021-08-09T00:00:00+00:00http://amplitudes.org/amplitudes/2108_03828<h1 id="links">Link(s):</h1>
<p>Paper and ancilary files.</p>
<ul>
<li><a href="https://arxiv.org/abs/2108.03828">Analytic results for two-loop planar master integrals for Bhabha scattering</a></li>
<li><a href="https://arxiv.org/src/2108.03828/anc">ancilary files</a></li>
</ul>
<h1 id="authors">Author(s):</h1>
<p>Claude Duhr, Vladimir A. Smirnov, Lorenzo Tancredi</p>
<h1 id="abstract">Abstract:</h1>
<p>We analytically evaluate the master integrals for the second type of planar contributions to the massive two-loop Bhabha scattering in QED using differential equa- tions with canonical bases. We obtain results in terms of multiple polylogarithms for all the master integrals but one, for which we derive a compact result in terms of elliptic mul- tiple polylogarithms. As a byproduct, we also provide a compact analytic result in terms of elliptic multiple polylogarithms for an integral belonging to the first family of planar Bhabha integrals, whose computation in terms of polylogarithms was addressed previously in the literature.</p>John Joseph M. Carrascohttp://prettyquestions.comPaper and ancillary files.Covariant Color-Kinematics Duality2021-08-04T00:00:00+00:002021-08-04T00:00:00+00:00http://amplitudes.org/amplitudes/2108_02276<h1 id="links">Link(s):</h1>
<p>Paper and ancilary files.</p>
<ul>
<li><a href="https://arxiv.org/abs/2108.02276">Covariant Color-Kinematics Duality</a></li>
<li><a href="https://arxiv.org/src/2108.02276/anc">ancilary files</a></li>
</ul>
<h1 id="authors">Author(s):</h1>
<p>Clifford Cheung, James Mangan</p>
<h1 id="abstract">Abstract:</h1>
<p>We show that color-kinematics duality is a manifest property of the equations of motion governing currents and field strengths. For the nonlinear sigma model (NLSM), this insight enables an implementation of the double copy at the level of fields, as well as an explicit construction of the kinematic algebra and associated kinematic current. As a byproduct, we also derive new formulations of the special Galileon (SG) and Born-Infeld (BI) theory. For Yang-Mills (YM) theory, this same approach reveals a novel structure – covariant color-kinematics duality – whose only difference from the conventional duality is that $1/\Box$ is replaced with covariant $1/D^2$. Remarkably, this structure implies that YM theory is itself the covariant double copy of gauged biadjoint scalar (GBAS) theory and an $F^3$ theory of field strengths encoding a corresponding kinematic algebra and current. Directly applying the double copy to equations of motion, we derive general relativity (GR) from the product of Einstein-YM and $F^3$ theory. This exercise reveals a trivial variant of the classical double copy that recasts any solution of GR as a solution of YM theory in a curved background. Covariant color-kinematics duality also implies a new decomposition of tree-level amplitudes in YM theory into those of GBAS theory. Using this representation we derive a closed-form, analytic expression for all BCJ numerators in YM theory and the NLSM for any number of particles in any spacetime dimension. By virtue of the double copy, this constitutes an explicit formula for all tree-level scattering amplitudes in YM, GR, NLSM, SG, and BI.</p>John Joseph M. Carrascohttp://prettyquestions.comPaper and ancillary files.