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Caltech Authors (162.774 recursos)

Repository of works by Caltech published authors.

Type = Report or Paper

Mostrando recursos 1 - 20 de 3.051

  1. Micro-resonator soliton generated directly with a diode laser

    Volet, Nicolas; Yi, Xu; Yang, Qi-Fan; Stanton, Eric J.; Morton, Paul A.; Yang, Ki Youl; Vahala, Kerry J.; Bowers, John E.
    An external-cavity diode laser is reported with ultralow noise, high power coupled to a fiber, and fast tunability. These characteristics enable the generation of an optical frequency comb in a silica micro-resonator with a single-soliton state. Neither an optical modulator nor an amplifier was used in the experiment. This demonstration greatly simplifies the soliton generation setup and represents a significant step forward to a fully integrated soliton comb system.

  2. Searching for Exoplanets Using a Microresonator Astrocomb

    Suh, Myoung-Gyun; Yi, Xu; Lai, Yu-Hung; Leifer, S.; Grudinin, Ivan S.; Vasisht, G.; Martin, Emily C.; Fitzgerald, Michael P.; Doppmann, G.; Wang, J.; Mawet, D.; Papp, Scott B.; Diddams, Scott A.; Beichman, C.; Vahala, Kerry
    Detection of weak radial velocity shifts of host stars induced by orbiting planets is an important technique for discovering and characterizing planets beyond our solar system. Optical frequency combs enable calibration of stellar radial velocity shifts at levels required for detection of Earth analogs. A new chip-based device, the Kerr soliton microcomb, has properties ideal for ubiquitous application outside the lab and even in future space-borne instruments. Moreover, microcomb spectra are ideally suited for astronomical spectrograph calibration and eliminate filtering steps required by conventional mode-locked-laser frequency combs. Here, for the calibration of astronomical spectrographs, we demonstrate an atomic/molecular line-referenced, near-infrared...

  3. Double-Trace Deformations of Conformal Correlations

    Giombi, Simone; Kirilin, Vladimir; Perlmutter, Eric
    Large N conformal field theories often admit unitary renormalization group flows triggered by double-trace deformations. We compute the change in scalar four-point functions under double-trace flow, to leading order in 1/N. This has a simple dual in AdS, where the flow is implemented by a change of boundary conditions, and provides a physical interpretation of single-valued conformal partial waves. We extract the change in the conformal dimensions and three-point coefficients of infinite families of double-trace composite operators. Some of these quantities are found to be sign-definite under double-trace flow. As an application, we derive anomalous dimensions of spinning double-trace operators...

  4. Vector Effective Field Theories from Soft Limits

    Cheung, Clifford; Kampf, Karol; Novotny, Jiri; Shen, Chia-Hsien; Trnka, Jaroslav; Wen, Congkao
    We present a bottom-up construction of vector effective field theories using the infrared structure of scattering amplitudes. Our results employ two distinct probes of soft kinematics: multiple soft limits and single soft limits after dimensional reduction, applicable in four and general dimensions, respectively. Both approaches uniquely specify the Born-Infeld (BI) model as the only theory of vectors completely fixed by certain infrared conditions which generalize the Adler zero for pions. These soft properties imply new recursion relations for on-shell scattering amplitudes in BI theory and suggest the existence of a wider class of vector effective field theories.

  5. Beyond Falsifiability: Normal Science in a Multiverse

    Carroll, Sean M.
    Cosmological models that invoke a multiverse - a collection of unobservable regions of space where conditions are very different from the region around us - are controversial, on the grounds that unobservable phenomena shouldn't play a crucial role in legitimate scientific theories. I argue that the way we evaluate multiverse models is precisely the same as the way we evaluate any other models, on the basis of abduction, Bayesian inference, and empirical success. There is no scientifically respectable way to do cosmology without taking into account different possibilities for what the universe might be like outside our horizon. Multiverse theories are utterly conventionally scientific, even if evaluating them can...

  6. Decentralization and the Gamble for Unity

    Gibilisco, Michael
    I reconcile competing accounts of decentralization and its effect on secessionist mobilization by endogenizing the regional minority’s grievance level in a dynamic framework. I demonstrate that decentralized institutions may have higher rates of minority unrest than their more centralized counterparts, and vice versa. Federations with moderate levels of power-sharing arrangements are particularly prone to secessionist violence. Even optimally chosen levels of decentralization can be followed by outbursts of minority protest or rebellion as the government subsequently refrains from repression in order to generate enough good will for a lasting peace. More broadly, grievances have a non-monotonic relationship with the onset and duration...

  7. Hox-logic of preadaptations for social insect symbiosis in rove beetles

    Parker, Joseph; Eldredge, K. Taro; Thomas, Isaiah M.; Coleman, Rory; Davis, Steven R.
    How symbiotic lifestyles evolve from free-living ecologies is poorly understood. Novel traits mediating symbioses may stem from preadaptations: features of free-living ancestors that predispose taxa to engage in nascent interspecies relationships. In Metazoa's largest family, Staphylinidae (rove beetles), the body plan within the subfamily Aleocharinae is preadaptive for symbioses with social insects. Short elytra expose a pliable abdomen that bears targetable glands for host manipulation or chemical defense. The exposed abdomen has also been convergently refashioned into ant- and termite-mimicking shapes in multiple symbiotic lineages. Here we show how this preadaptive anatomy evolved via novel Hox gene functions that remodeled...

  8. Lecture notes on Turbulent Fluid Motion

    Burgers, J. M.
    Lecture notes of prof. Burgers prepared during his sabbatical at CalTech.

  9. A Testbed Experiment of a (Smart) Marked Based, Student Transportation Policy: Non Convexities, Coordination, Non Existence

    Lee, Hsing Yang; Maron, Travis; Plott, Charles R.; Seo, Han
    The paper develops and studies a decentralized mechanism for pricing and allocation challenges typically met with administrative processes. Traditional forms of markets are not used due to conditions associated with market failure, such as complex coordination problems, thin markets, non-convexities including and zero marginal cost due to lumpy transportation capacities. The mechanism rests on an assignment process that is guided by a computational process, enforces rules and channels information feedback to participants. Special, testbed experimental methods produce high levels of efficiency when confronted by individual behaviors that are consistent with traditional models of strategic behavior.

  10. KELT-21b: A Hot Jupiter Transiting the Rapidly-Rotating Metal-Poor Late-A Primary of a Likely Hierarchical Triple System

    Johnson, Marshall C.; Calchi Novati, Sebastiano; Fulton, Benjamin J.
    We present the discovery of KELT-21b, a hot Jupiter transiting the V=10.5 A8V star HD 332124. The planet has an orbital period of P = 3.6127647 ± 0.0000033 days and a radius of 1.586^(+0.039)_(-0.040) R_J. We set an upper limit on the planetary mass of M_P < 3.91 M_J at 3σ confidence. We confirmed the planetary nature of the transiting companion using this mass limit and Doppler tomographic observations to verify that the companion transits HD 332124. These data also demonstrate that the planetary orbit is well-aligned with the stellar spin, with a sky-projected spin-orbit misalignment of λ=−5.6^(+1.7∘)_(-1.9). The star...

  11. Reconciling observed and simulated stellar halo masses

    Sanderson, Robyn E.; Garrison-Kimmel, Shea; Wetzel, Andrew; Chan, Tsang Keung; Hopkins, Philip F.; Kereš, Dušan; Escala, Ivanna; Faucher-Giguère, Claude-André; Ma, Xiangcheng
    We use cosmological hydrodynamical simulations of Milky-Way-mass galaxies from the FIRE project to evaluate various strategies for estimating the mass of a galaxy's accreted stellar halo from deep, integrated-light images. We find good agreement with observations if we mimic observational methods to measure the mass of a stellar "halo" component, selecting stars via projected radius relative to the disk scale length or by their surface brightness. However, these observational methods systematically underestimate the true stellar halo mass, defined in the simulation as the mass of accreted stars formed outside of the host galaxy, by up to a factor of ten. Furthermore, these observational selection strategies introduce spurious dependencies on...

  12. Systematic calibration error requirements for gravitational-wave detectors via the Cramér-Rao bound

    Hall, Evan D.; Cahillane, Craig; Izumi, Kiwamu; Smith, Rory J. E.; Adhikari, Rana X.
    Gravitational-wave (GW) laser interferometers such as Advanced LIGO transduce spacetime strain into optical power fluctuation. Converting this optical power fluctuations back into an estimated spacetime strain requires a calibration process that accounts for both the interferometer's optomechanical response and the feedback control loop used to control the interferometer test masses. Systematic errors in the calibration parameters lead to systematic errors in the GW strain estimate, and hence to systematic errors in the astrophysical parameter estimates in a particular GW signal. In this work we examine this effect for a GW signal similar to GW150914, both for a low-power detector operation similar to the first and second Advanced LIGO observing...

  13. Branches of the Black Hole Wave Function Need Not Contain Firewalls

    Bao, Ning; Carroll, Sean M.; Chatwin-Davies, Aidan; Pollack, Jason; Remmen, Grant N.
    We discuss the branching structure of the quantum-gravitational wave function that describes the evaporation of a black hole. A global wave function that initially describes a classical Schwarzschild geometry is continually decohered into distinct semiclassical branches by the emission of Hawking radiation. The laws of quantum mechanics dictate that the wave function evolves unitarily, but this unitary evolution is only manifest when considering the global description of the wave function: it is not implemented by time evolution on a single semiclassical branch. Conversely, geometric notions like the position or smoothness of a horizon only make sense on the level of individual branches. We consider the implications of this picture...

  14. 4d N=1/2d Yang-Mills Duality in Holography

    Fluder, Martin
    We study the supergravity dual of four-dimensional N=1 superconformal field theories arising from wrapping M5-branes on a K\"ahler two-cycle inside a Calabi-Yau threefold. We derive an effective three-dimensional theory living on the cobordism between the infrared and ultraviolet Riemann surfaces, describing the renormalization group flows between AdS_7 and AdS_5 as well as between different AdS_5 fixed points. The realization of this system as an effective theory is convenient to make connections to known theories, and we show that upon imposing (physical) infrared boundary conditions, the effective three-dimensional theory further reduces to two-dimensional SU(2) Yang-Mills theory on the Riemann surface, thus...

  15. From CFT to Ramond super-quantum curves

    Ciosmak, Paweł; Hadasz, Leszek; Jaskólski, Zbigniew; Manabe, Masahide; Sułkowski, Piotr
    As we have shown in the previous work, using the formalism of matrix and eigenvalue models, to a given classical algebraic curve one can associate an infinite family of quantum curves, which are in one-to-one correspondence with singular vectors of a certain (e.g. Virasoro or super-Virasoro) underlying algebra. In this paper we reformulate this problem in the language of conformal field theory. Such a reformulation has several advantages: it leads to the identification of quantum curves more efficiently, it proves in full generality that they indeed have the structure of singular vectors, it enables identification of corresponding eigenvalue models. Moreover, this approach can be easily generalized to other underlying...

  16. Resummed Photon Spectra for WIMP Annihilation

    Baumgart, Matthew; Cohen, Timothy; Moult, Ian; Rodd, Nicholas L.; Slatyer, Tracy R.; Solon, Mikhail P.; Stewart, Iain W.; Vaidya, Varun
    We construct an effective field theory (EFT) description of the hard photon spectrum for heavy WIMP annihilation. This facilitates precision predictions relevant for line searches, and allows the incorporation of non-trivial energy resolution effects. Our framework combines techniques from non-relativistic EFTs and soft-collinear effective theory (SCET), as well as its multi-scale extensions that have been recently introduced for studying jet substructure. We find a number of interesting features, including the simultaneous presence of SCET$_{\text{I}}$ and SCET$_{\text{II}}$ modes, as well as collinear-soft modes at the electroweak scale. We derive a factorization formula that enables both the resummation of the leading large Sudakov double logarithms that appear in the...

  17. Loop-Induced Stochastic Bias at Small Wavevectors

    McAneny, Michael; Ridgway, Alexander K.; Solon, Mikhail P.; Wise, Mark B.
    Primordial non-Gaussianities enhanced at small wavevectors can induce a power spectrum of the galaxy overdensity that differs greatly from that of the matter overdensity at large length scales. In previous work, it was shown that "squeezed" three-point and "collapsed" four-point functions of the curvature perturbation $\zeta$ can generate these non-Gaussianities and give rise to so-called scale-dependent and stochastic bias in the galaxy overdensity power spectrum. We explore a third way to generate non-Gaussianities enhanced at small wavevectors: the infrared behavior of quantum loop contributions to the four-point correlations of $\zeta$. We show that these loop effects lead to stochastic bias, which can be observable in the context of quasi-single...

  18. A 2d (0,2) appetizer

    Dedushenko, Mykola; Gukov, Sergei
    Searching for the simplest non-abelian 2d gauge theory with N=(0,2) supersymmetry and non-trivial IR physics, we propose a new duality for SU(2) SQCD with Nf=4 chiral flavors. The chiral algebra of this theory is found to be so(8)−2, the same as in 4d N=2 SU(2) gauge theory with four hypermultiplets

  19. Note on Green Function Formalism and Topological Invariants

    Zhou, Yehao; Liu, Junyu
    It has been discovered previously that the topological order parameter could be identified from the topological data of the Green function, namely the (generalized) TKNN invariant in general dimensions, for both non-interacting and interacting systems. In this note, we show that this phenomena has a clear geometric derivation. This proposal could be regarded as an alternative proof for the identification of the corresponding topological invariant and topological order parameter.

  20. Coulomb Branch Operators and Mirror Symmetry in Three Dimensions

    Dedushenko, Mykola; Fan, Yale; Pufu, Silviu S.; Yacoby, Ran
    We develop new techniques for computing exact correlation functions of a class of local operators, including certain monopole operators, in three-dimensional N=4 abelian gauge theories that have superconformal infrared limits. These operators are position-dependent linear combinations of Coulomb branch operators. They form a one-dimensional topological algebra that encodes a deformation quantization of the Coulomb branch chiral ring, and their correlation functions completely fix the (n≤3)-point functions of all half-BPS Coulomb branch operators. Using these results, we provide new derivations of the conformal dimension of half-BPS monopole operators as well as new and detailed tests of mirror symmetry. Our main approach...

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