Recursos de colección
Caltech Authors (147.369 recursos)
Repository of works by Caltech published authors.
Group = Walter Burke Institute for Theoretical Physics
Repository of works by Caltech published authors.
Group = Walter Burke Institute for Theoretical Physics
Hellerman, Simeon; Kobayashi, Nozomu; Maeda, Shunsuke; Watanabe, Masataka
In this note we search for the ground state, in infinite volume, of the D = 3 WilsonFisher conformal O(4) model, at nonzero values of the two independent charge densities ρ1,2 . Using an effective theory valid on scales longer than the scale defined by the charge density, we show that the ground-state configuration is inhomogeneous for generic ratios ρ1 /ρ2 . This result confirms, within the context of a well-defined effective theory, a recent no-go result of  . We also show that any spatially periodic ground state solutions have an energetic preference towards longer periods, within some range of ρ1/ρ2 containing a neighborhood of zero. This suggests that...
Cuomo, Gabriel Francisco; Karateev, Denis; Kravchuk, Petr
We provide a framework for generic 4D conformal bootstrap computations. It is based on the unification of two independent approaches, the covariant (embedding) formalism and the non-covariant (conformal frame) formalism. We construct their main ingredients (tensor structures and differential operators) and establish a precise connection between them. We supplement the discussion by additional details like classification of tensor structures of n-point functions, normalization of 2-point functions and seed conformal blocks, Casimir differential operators and treatment of conserved operators and permutation symmetries. Finally, we implement our framework in a Mathematica package and make it freely available.
Chang, Chi-Ming; Lin, Ying-Hsuan
We bootstrap N = (1, 0) superconformal field theories in six dimensions, by analyzing the four-point function of flavor current multiplets. Assuming E8 flavor group, we present universal bounds on the central charge CT and the flavor central charge CJ . Based on the numerical data, we conjecture that the rank-one E-string theory saturates the universal lower bound on CJ , and numerically determine the spectrum of long multiplets in the rank-one E-string theory. We comment on the possibility of solving the higher-rank E-string theories by bootstrap and thereby probing M-theory on AdS7 × S^4/Z_2.
Cheung, Clifford; Shen, Chia-Hsien; Wen, Congkao
We derive new amplitudes relations revealing a hidden unity among wide-ranging theories in arbitrary spacetime dimensions. Our results rely on a set of Lorentz invariant differential operators which transmute physical tree-level scattering amplitudes into new ones. By transmuting the amplitudes of gravity coupled to a dilaton and two-form, we generate all the amplitudes of Einstein-Yang-Mills theory, Dirac-Born-Infield theory, special Galileon, nonlinear sigma model, and biadjoint scalar theory. Transmutation also relates amplitudes in string theory and its variants. As a corollary, celebrated aspects of gluon and graviton scattering like color-kinematics duality, the KLT relations, and the CHY construction are inherited traits of the transmuted amplitudes. Transmutation recasts the Adler zero as...
Dedushenko, Mykola; Gukov, Sergei; Putrov, Pavel
We propose a way of computing 4-manifold invariants, old and new, as chiral correlation functions in half-twisted 2d N = (0, 2) theories that arise from compactification of fivebranes. Such formulation gives a new interpretation of some known statements about Seiberg-Witten invariants, such as the basic class condition, and gives a prediction for structural properties of the multi-monopole invariants and their non-abelian generalizations.
Squire, J.; Schekochihin, A. A.; Quataert, E.
This work, which extends Squire et al (Astrophys. J. Lett. 2016 830 L25), explores the effect of self-generated pressure anisotropy on linearly polarized shear-Alfvén fluctuations in low-collisionality plasmas. Such anisotropies lead to stringent limits on the amplitude of magnetic perturbations in high-β plasmas, above which a fluctuation can destabilize itself through the parallel firehose instability. This causes the wave frequency to approach zero, 'interrupting' the wave and stopping its oscillation. These effects are explored in detail in the collisionless and weakly collisional 'Braginskii' regime, for both standing and traveling waves. The focus is on simplified models in one dimension, on...
Cheung, Clifford; Remmen, Grant N.
We derive new representations of the Einstein-Hilbert action in which graviton perturbation theory is immensely simplified. To accomplish this, we recast the Einstein-Hilbert action as a theory of purely cubic interactions among gravitons and a single auxiliary field. The corresponding equations of motion are the Einstein field equations rewritten as two coupled first-order differential equations. Since all Feynman diagrams are cubic, we are able to derive new off-shell recursion relations for tree-level graviton scattering amplitudes. With a judicious choice of gauge fixing, we then construct an especially compact form for the Einstein-Hilbert action in which all graviton interactions are simply proportional to the graviton kinetic term. Our results apply to...
Anderson, Kassandra R.; Lai, Dong; Storch, Natalia I.
Eclipsing binaries are observed to have a range of eccentricities and spin-orbit misalignments (stellar obliquities). Whether such properties are primordial or arise from post-formation dynamical interactions remains uncertain. This paper considers the scenario in which the binary is the inner component of a hierarchical triple stellar system, and derives the requirements that the tertiary companion must satisfy in order to raise the eccentricity and obliquity of the inner binary. Through numerical integrations of the secular octupole-order equations of motion of stellar triples, coupled with the spin precession of the oblate primary star due to the torque from the secondary, we...
Pablo, Herbert; Richardson, N. D.; Fuller, J.; Rowe, J.; Moffatt, A. F. J.; Kuschnig, R.; Popowicz, A.; Handler, G.; Neiner, C.; Pigulski, A.; Wade, G. A.; Weiss, W.; Buysschaert, B.; Ramiaramanantsoa, T.; Bratcher, A. D.; Gerhartz, C. J.; Greco, J. J.; Hardegree-Ullman, K.; Lembryk, L.; Oswald, W. L.
ι Ori is a well-studied massive binary consisting of an O9 III + B1 III/IV star. Due to its high eccentricity (e = 0.764) and short orbital period (Porb = 29.133 76 d), it has been considered to be a good candidate to show evidence of tidal effects; however, none have previously been identified. Using photometry from the BRIght Target Explorer (BRITE)-Constellation space photometry mission, we have confirmed the existence of tidal distortions through the presence of a heartbeat signal at periastron. We combine spectroscopic and light-curve analyses to measure the masses and radii of the components, revealing ι Ori...
Bao, Ning; Carroll, Sean M.; Singh, Ashmeet
We argue in a model-independent way that the Hilbert space of quantum gravity is locally finite-dimensional. In other words, the density operator describing the state corresponding to a small region of space, when such a notion makes sense, is defined on a finite-dimensional factor of a larger Hilbert space. Because quantum gravity potentially describes superpo- sitions of different geometries, it is crucial that we associate Hilbert-space factors with spatial regions only on individual decohered branches of the universal wave function. We discuss some implications of this claim, including the fact that quantum field theory cannot be a fundamental description of Nature.
Bourjaily, Jacob L.; Herrmann, Enrico; Trnka, Jaroslav
We introduce a prescriptive approach to generalized unitarity, resulting in a strictly-diagonal basis of loop integrands with coefficients given by specifically-tailored residues in field theory. We illustrate the power of this strategy in the case of planar, maximally supersymmetric Yang-Mills theory, where we construct closed-form representations of all ($n$-point N$^k$MHV) scattering amplitudes through three loops. The prescriptive approach contrasts with the ordinary description of unitarity-based methods by avoiding any need for linear algebra to determine integrand coefficients. We describe this approach in general terms as it should have applications to many quantum field theories, including those without planarity, supersymmetry, or massless spectra defined in any number of dimensions.
I summarize, at its 41st--and what would have been Bruno's 94th-birthday, the history of the discoveries of Supergravity.
Nagakura, Hiroki; Iwakami, Wakana; Furusawa, Shun; Sumiyoshi, Kohsuke; Yamada, Shoichi; Matsufuru, Hideo; Imakura, Akira
We present a newly developed moving-mesh technique for the multi-dimensional Boltzmann-Hydro code for the simulation of core-collapse supernovae (CCSNe). What makes this technique different from others is the fact that it treats not only hydrodynamics but also neutrino transfer in the language of the 3 + 1 formalism of general relativity (GR), making use of the shift vector to specify the time evolution of the coordinate system. This means that the transport part of our code is essentially general relativistic, although in this paper it is applied only to the moving curvilinear coordinates in the flat Minknowski spacetime, since the...
Yang, Huan; Yagi, Kent; Blackman, Jonathan; Lehner, Luis; Paschalidis, Vasileios; Pretorius, Frans; Yunes, Nicolás
The measurement of multiple ringdown modes in gravitational waves from binary black hole mergers will allow for testing the fundamental properties of black holes in general relativity and to constrain modified theories of gravity. To enhance the ability of Advanced LIGO/Virgo to perform such tasks, we propose a coherent mode stacking method to search for a chosen target mode within a collection of multiple merger events. We first rescale each signal so that the target mode in each of them has the same frequency and then sum the waveforms constructively. A crucial element to realize this coherent superposition is to...
Cheung, Clifford; de la Fuente, Anton; Sundrum, Raman
We reformulate the scattering amplitudes of 4D flat space gauge theory and gravity in the language of a 2D CFT on the celestial sphere. The resulting CFT structure exhibits an OPE constructed from 4D collinear singularities, as well as infinite-dimensional Kac-Moody and Virasoro algebras encoding the asymptotic symmetries of 4D flat space. We derive these results by recasting 4D dynamics in terms of a convenient foliation of flat space into 3D Euclidean AdS and Lorentzian dS geometries. Tree-level scattering amplitudes take the form of Witten diagrams for a continuum of (A)dS modes, which are in turn equivalent to CFT correlators...
Harada, A.; Nagakura, H.; Iwakami, W.; Yamada, S.
We investigate the criterion for the acoustic mechanism to work successfully in core-collapse supernovae. The acoustic mechanism is an alternative to the neutrino-heating mechanism. It was proposed by Burrows et al., who claimed that acoustic waves emitted by g-mode oscillations in proto-neutron stars (PNS) energize a stalled shock wave and eventually induce an explosion. Previous works mainly studied to which extent the g-modes are excited in the PNS. In this paper, on the other hand, we investigate how strong the acoustic wave needs to be if it were to revive a stalled shock wave. By adding the acoustic power as...
Carroll, Sean M.; Chatwin-Davies, Aidan
In a wide class of cosmological models, a positive cosmological constant drives cosmological evolution toward an asymptotically de Sitter phase. Here we connect this behavior to the increase of entropy over time, based on the idea that de Sitter space is a maximum-entropy state. We prove a cosmic no-hair theorem for Robertson-Walker and Bianchi I spacetimes by assuming that the generalized entropy of a Q-screen ("quantum" holographic screen), in the sense of the cosmological version of the Generalized Second Law conjectured by Bousso and Engelhardt, increases up to a finite maximum value, which we show coincides with the de Sitter horizon entropy. We do not use the Einstein...
Carroll, Sean M.; Remmen, Grant N.
We construct a model in which the cosmological constant is canceled from the gravitational equations of motion. Our model relies on two key ingredients: a nonlocal constraint on the action, which forces the spacetime average of the Lagrangian density to vanish, and a dynamical way for this condition to be satisfied classically with arbitrary matter content. We implement the former condition with a spatially-constant Lagrange multiplier associated with the volume form and the latter by including a free four-form gauge field strength in the action. These two features are enough to remove the cosmological constant from the Einstein equation. The model is consistent with all cosmological and experimental bounds...
Morozova, Viktoriya; Piro, Anthony L.; Valenti, Stefano
A longstanding problem in the study of supernovae (SNe) has been the relationship between the Type IIP and Type IIL subclasses. Whether they come from distinct progenitors or they are from similar stars with some property that smoothly transitions from one class to another has been the subject of much debate. Here, using one-dimensional radiation-hydrodynamic SN models, we show that the multi-band light curves of SNe IIL are well fit by ordinary red supergiants surrounded by dense circumstellar material (CSM). The inferred extent of this material, coupled with a typical wind velocity of ~10-100 km s^(-1), suggests enhanced activity by...
Kameyama, Masaya; Nawata, Satoshi
We formulate large N duality of U(N) refined Chern-Simons theory with a torus knot/link in S^3. By studying refined BPS states in M-theory, we provide the explicit form of low-energy effective actions of Type IIA string theory with D4-branes on the Ω-background. This form enables us to relate refined Chern-Simons invariants of a torus knot/link in S^3 to refined BPS invariants in the resolved conifold. Assuming that the extra U(1) global symmetry acts on BPS states trivially, the duality predicts graded dimensions of cohomology groups of moduli spaces of M2-M5 bound states associated to a torus knot/link in the resolved conifold.