Recursos de colección

Caltech Authors (170.931 recursos)

Repository of works by Caltech published authors.

Group = Walter Burke Institute for Theoretical Physics

Mostrando recursos 1 - 20 de 247

  1. A spacetime derivation of the Lorentzian OPE inversion formula

    Simmons-Duffin, David; Stanford, Douglas; Witten, Edward
    Caron-Huot has recently given an interesting formula that determines OPE data in a conformal field theory in terms of a weighted integral of the four-point function over a Lorentzian region of cross-ratio space. We give a new derivation of this formula based on Wick rotation in spacetime rather than cross-ratio space. The derivation is simple in two dimensions but more involved in higher dimensions. We also derive a Lorentzian inversion formula in one dimension that sheds light on previous observations about the chaos regime in the SYK model.

  2. Four-dimensional lens space index from two-dimensional chiral algebra

    Fluder, Martin; Song, Jaewon
    We study the supersymmetric partition function on S^1 × L(r, 1), or the lens space index of four-dimensional N=2 superconformal field theories and their connection to two-dimensional chiral algebras. We primarily focus on free theories as well as ArgyresDouglas theories of type (A_1, A_k) and (A_1, D_k). We observe that in specific limits, the lens space index is reproduced in terms of the (refined) character of an appropriately twisted module of the associated two-dimensional chiral algebra or a generalized vertex operator algebra. The particular twisted module is determined by the choice of discrete holonomies for the flavor symmetry in four-dimensions.

  3. Evidence for a quantum-spin-Hall phase in graphene decorated with Bi_2Te_3 nanoparticles

    Hatsuda, K.; Mine, H.; Nakamura, T.; Li, J.; Wu, R.; Alicea, J.; Katsumoto, S.; Haruyama, J.
    Realization of the quantum-spin-Hall effect in graphene devices has remained an outstanding challenge dating back to the inception of the field of topological insulators. Graphene's exceptionally weak spin-orbit coupling-stemming from carbon's low mass-poses the primary obstacle. We experimentally and theoretically study artificially enhanced spin-orbit coupling in graphene via random decoration with dilute Bi2Te3 nanoparticles. Remarkably, multi-terminal resistance measurements suggest the presence of helical edge states characteristic of a quantum-spin-Hall phase; those magnetic-field dependence, X-ray photoelectron spectra, scanning tunneling spectroscopy, and first-principles calculations further support this scenario. These observations highlight a pathway to spintronics and quantum-information applications in graphene-based quantum-spin-Hall platforms.

  4. Modeling Position and Momentum in Finite-Dimensional Hilbert Spaces via Generalized Clifford Algebra

    Singh, Ashmeet; Carroll, Sean M.
    The finite entropy of black holes suggests that local regions of spacetime are described by finite-dimensional factors of Hilbert space, in contrast with the infinite-dimensional Hilbert spaces of quantum field theory. With this in mind, we explore how to cast finite-dimensional quantum mechanics in a form that matches naturally onto the smooth case, especially the recovery of conjugate position/momentum variables, in the limit of large Hilbert-space dimension. A natural tool for this task is the generalized Clifford algebra (GCA). Based on an exponential form of Heisenberg's canonical commutation relation, the GCA offers a finite-dimensional generalization of conjugate variables without relying on any a priori structure on Hilbert space. We highlight...

  5. Fracton topological order from the Higgs and partial-confinement mechanisms of rank-two gauge theory

    Ma, Han; Hermele, Michael; Chen, Xie
    Fractons are gapped pointlike excitations in d=3 topological ordered phases whose motion is constrained. They have been discovered in several gapped models but a unifying physical mechanism for generating them is still missing. It has been noticed that in symmetric-tensor U(1) gauge theories, charges are fractons and cannot move freely due to, for example, the conservation of not only the charge but also the dipole moment. To connect these theories with fully gapped fracton models, we study Higgs and partial confinement mechanisms in rank-2 symmetric-tensor gauge theories, where charges or magnetic excitations, respectively, are condensed. Specifically, we describe two different...

  6. Cutoff AdS_3 versus the TT[bar] deformation

    Kraus, Per; Liu, Junyu; Marolf, Donald
    A recent proposal relates two dimensional holographic conformal field theories deformed by the integrable TT[bar] flow to AdS_3 with a finite radial cutoff. We investigate this proposal by studying perturbative correlation functions on the two sides. For low point correlators of the stress tensor, we successfully match the deformed CFT results at large central charge to bulk results obtained in classical pure gravity. The deformed CFT also provides definite predictions for loop corrections in the bulk. We then include matter fields in the bulk. To reproduce the classical bulk two-point function of a scalar operator we show that the deformed...

  7. Resonant drag instabilities in protoplanetary discs: the streaming instability and new, faster growing instabilities

    Squire, Jonathan; Hopkins, Philip F.
    We identify and study a number of new, rapidly growing instabilities of dust grains in protoplanetary discs, which may be important for planetesimal formation. The study is based on the recognition that dust–gas mixtures are generically unstable to a resonant drag instability (RDI), whenever the gas, absent dust, supports undamped linear modes. We show that the ‘streaming instability’ is an RDI associated with epicyclic oscillations; this provides simple interpretations for its mechanisms and accurate analytic expressions for its growth rates and fastest growing wavelengths. We extend this analysis to more general dust streaming motions and other waves, including buoyancy and...

  8. Low-mass X-ray binaries from black hole retaining globular clusters

    Giesler, Matthew; Clausen, Drew; Ott, Christian D.
    Recent studies suggest that globular clusters (GCs) may retain a substantial population of stellar-mass black holes (BHs), in contrast to the long-held belief of a few to zero BHs. We model the population of BH low-mass X-ray binaries (BH-LMXBs), an ideal observable proxy for elusive single BHs, produced from a representative group of Milky Way GCs with variable BH populations. We simulate the formation of BH binaries in GCs through exchange interactions between binary and single stars in the company of tens to hundreds of BHs. Additionally, we consider the impact of the BH population on the rate of compact...

  9. On topological approach to local theory of surfaces in Calabi–Yau threefolds

    Gukov, Sergei; Liu, Chiu-Chu Melissa; Sheshmani, Artan; Yau, Shing-Tung
    We study the web of dualities relating various enumerative invariants, notably Gromov–Witten invariants and invariants that arise in topological gauge theory. In particular, we study Donaldson–Thomas gauge theory and its reductions to D=4D=4 and D=2D=2 which are relevant to the local theory of surfaces in Calabi–Yau threefolds.

  10. Commuting-projector Hamiltonians for chiral topological phases built from parafermions

    Son, Jun Ho; Alicea, Jason
    We introduce a family of commuting-projector Hamiltonians whose degrees of freedom involve ℤ_3 parafermion zero modes residing in a parent fractional-quantum-Hall fluid. These commuting-projector models inherit nontrivial Hall conductance from the parent quantum-Hall states in which they are defined, and thus can describe chiral topological phases. The two simplest models in this family emerge from dressing Ising-paramagnet and toric-code spin models with parafermions; we study their edge properties, anyonic excitations, and ground-state degeneracy. We show that the first model realizes a symmetry-enriched topological phase (SET) for which ℤ_2 spin-flip symmetry from the Ising paramagnet permutes the anyons. Interestingly, the interface...

  11. Recursive Soft Drop

    Dreyer, Frédéric A.; Necib, Lina; Soyez, Gregory; Thaler, Jesse
    We introduce a new jet substructure technique called Recursive Soft Drop, which generalizes the Soft Drop algorithm to have multiple grooming layers. Like the original Soft Drop method, this new recursive variant traverses a jet clustering tree to remove soft wide-angle contamination. By enforcing the Soft Drop condition N times, Recursive Soft Drop improves the jet mass resolution for boosted hadronic objects like W bosons, top quarks, and Higgs bosons. We further show that this improvement in mass resolution persists when including the effects of pileup, up to large pileup multiplicities. In the limit that N goes to infinity, the...

  12. De-Sitter Quantum Loops as the origin of Primordial Non-Gaussianities

    An, Haipeng; Wise, Mark B.; Zhang, Zipei
    It was pointed out recently that in some inflationary models quantum loops containing a scalar of mass m that couples to the inflaton can be the dominant source of primordial non-Gaussianities. We explore this phenomenon in the simplest such model focusing on the behavior of the primordial curvature fluctuations for small m/H. Explicit calculations are done for the three and four point curvature fluctuation correlations. Constraints on the parameters of the model from the CMB limits on primordial non-Gaussianity are discussed. The bi-spectrum in the squeezed limit and the tri-spectrum in the compressed limit are examined. The form of the n-point correlations as any partial sum of wave vectors...

  13. Spectral form factors and late time quantum chaos

    Liu, Junyu
    This is a collection of notes that are about spectral form factors of standard ensembles in the random matrix theory, written for the practical usage of current study of late time quantum chaos. More precisely, we consider Gaussian Unitary Ensemble (GUE), Gaussian Orthogonal Ensemble (GOE), Gaussian Symplectic Ensemble (GSE), Wishart-Laguerre Unitary Ensemble (LUE), Wishart-Laguerre Orthogonal Ensemble (LOE), and Wishart-Laguerre Symplectic Ensemble (LSE). These results and their physics applications cover a three-fold classification of late time quantum chaos in terms of spectral form factors.

  14. Dual fluid for the Kerr black hole

    Lysov, Vyacheslav
    Rotating black holes are algebraically special solutions to the vacuum Einstein equation. Using properties of the algebraically special solutions we construct the dual fluid, which flows on black hole horizon. An explicit form of the Kerr solution allows us to write an explicit dual fluid solution and investigate its stability using energy balance equation. We show that the dual fluid is stable because of high algebraic speciality of the Kerr solution.

  15. Stochastic Bias from Loops of Massive Particles During Inflation

    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 ζ 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 ζ. We show that these loop effects can give the largest...

  16. Reconciling two notions of quantum operator disagreement: Entropic uncertainty relations and information scrambling, united through quasiprobabilities

    Yunger Halpern, Nicole; Bartolotta, Anthony; Pollack, Jason
    How violently do two quantum operators disagree? Different fields of physics feature different measures of incompatibility: (i) In quantum information theory, entropic uncertainty relations constrain measurement outcomes. (ii) In condensed matter and high-energy physics, the out-of-time-ordered correlator (OTOC) signals scrambling, the spread of information through many-body entanglement. We unite these measures, deriving entropic uncertainty relations for scrambling. The entropies are of distributions over weak and strong measurements' possible outcomes. Weakness causes the OTOC quasiprobability (a nonclassical generalization of a probability, in terms of which the OTOC decomposes) to govern terms in the uncertainty bound. Scrambling strengthens the bound, we show, in numerical simulations of a spin chain. Beyond scrambling, we derive...

  17. Resilience of scrambling measurements

    Swingle, Brian; Yunger Halpern, Nicole
    Most experimental protocols for measuring scrambling require time evolution with a Hamiltonian and with the Hamiltonian's negative counterpart (backward time evolution). Engineering controllable quantum many-body systems for which such forward and backward evolution is possible is a significant experimental challenge. Furthermore, if the system of interest is quantum chaotic, one might worry that any small errors in the time reversal will be rapidly amplified, obscuring the physics of scrambling. This paper undermines this expectation: We exhibit a renormalization protocol that extracts nearly ideal out-of-time-ordered-correlator measurements from imperfect experimental measurements. We analytically and numerically demonstrate the protocol's effectiveness, up to the...

  18. Coulomb branches with complex singularities

    Argyres, Philip C.; Martone, Mario
    We construct 4d superconformal field theories (SCFTs) whose Coulomb branches have singular complex structures. This implies, in particular, that their Coulomb branch coordinate rings are not freely generated. Our construction also gives examples of distinct SCFTs which have identical moduli space (Coulomb, Higgs, and mixed branch) geometries. These SCFTs thus provide an interesting arena in which to test the relationship between moduli space geometries and conformal field theory data. We construct these SCFTs by gauging certain discrete global symmetries of N = 4 superYang-Mills (sYM) theories. In the simplest cases, these discrete symmetries are outer automorphisms of the sYM gauge group,...

  19. Chaos and random matrices in supersymmetric SYK

    Hunter-Jones, Nicholas; Liu, Junyu
    We use random matrix theory to explore late-time chaos in supersymmetric quantum mechanical systems. Motivated by the recent study of supersymmetric SYK models and their random matrix classification, we consider the Wishart-Laguerre unitary ensemble and compute the spectral form factors and frame potentials to quantify chaos and randomness. Compared to the Gaussian ensembles, we observe the absence of a dip regime in the form factor and a slower approach to Haar-random dynamics. We find agreement between our random matrix analysis and predictions from the supersymmetric SYK model, and discuss the implications for supersymmetric chaotic systems.

  20. The S Matrix of 6D Super Yang-Mills and Maximal Supergravity from Rational Maps

    Cachazo, Freddy; Guevara, Alfredo; Heydeman, Matthew; Mizera, Sebastian; Schwarz, John H.; Wen, Congkao
    We present new formulas for n-particle tree-level scattering amplitudes of sixdimensional N = (1, 1) super Yang–Mills (SYM) and N = (2, 2) supergravity (SUGRA). They are written as integrals over the moduli space of certain rational maps localized on the (n − 3)! solutions of the scattering equations. Due to the properties of spinor-helicity variables in six dimensions, the even-n and odd-n formulas are quite different and have to be treated separately. We first propose a manifestly supersymmetric expression for the even-n amplitudes of N = (1, 1) SYM theory and perform various consistency checks. By considering soft-gluon limits of the even-n amplitudes, we deduce the...

Aviso de cookies: Usamos cookies propias y de terceros para mejorar nuestros servicios, para análisis estadístico y para mostrarle publicidad. Si continua navegando consideramos que acepta su uso en los términos establecidos en la Política de cookies.