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Caltech Authors (155.447 recursos)

Repository of works by Caltech published authors.

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Mostrando recursos 1 - 20 de 460

  1. The nature of X-ray spectral variability in MCG-6-30-15

    Kammoun, E. S.; Papadakis, I. E.
    The flux-flux plot (FFP) method can provide model-independent clues regarding the X-ray variability of active galactic nuclei. To use it properly, the bin size of the light curves should be as short as possible, provided the average counts in the light curve bins are larger than $\sim 200$. We apply the FFP method to the 2013, simultaneous XMM-Newton and NuSTAR observations of the Seyfert galaxy MCG$-$6-30-15, in the 0.3-40 keV range. The FFPs above $\sim 1.6$ keV are well-described by a straight line. This result rules out spectral slope variations and the hypothesis of absorption driven variability. Our results are fully consistent with a power-law component varying in normalization...

  2. Truncation of the Accretion Disk at One Third of the Eddington Limit in the Neutron Star Low-Mass X-ray Binary Aquila X-1

    Ludlam, Renee M.; Miller, Jon M.; Degenaar, Nathalie; Sanna, Andrea; Cackett, Edward M.; Altamirano, Diego; King, Ashley L.
    We perform a reflection study on a new observation of the neutron star low-mass X-ray binary Aquila X-1 taken with NuSTAR during the August 2016 outburst and compare with the July 2014 outburst. The source was captured at $\sim32\%\ L_{\mathrm{Edd}}$, which is over four times more luminous than the previous observation during the 2014 outburst. Both observations exhibit a broadened Fe line profile. Through reflection modeling, we determine that the inner disk is truncated $R_{in,\ 2016}=11_{-1}^{+2}\ R_{g}$ (where $R_{g}=GM/c^{2}$) and $R_{in,\ 2014}=14\pm2\ R_{g}$ (errors quoted at the 90% confidence level). Fiducial neutron star parameters (M$_{NS}=1.4$ M$_{\odot}$, $R_{NS}=10$ km) give a stellar radius of $R_{NS}=4.85\ R_{g}$; our measurements rule out a...

  3. The active nucleus of the ULIRG IRAS F00183-7111 viewed by NuSTAR

    Iwasawa, K.; Spoon, H. W. W.; Comastri, A.; Gilli, R.; Lanzuisi, G.; Piconcelli, E.; Vignali, C.; Brusa, M.; Puccetti, S.
    We present an X-ray study of the ultra-luminous infrared galaxy IRAS F00183-7111 (z=0.327), using data obtained from NuSTAR, Chandra X-ray Observatory, Suzaku and XMM-Newton. The Chandra imaging shows that a point-like X-ray source is located at the nucleus of the galaxy at energies above 2 keV. However, the point source resolves into diffuse emission at lower energies, extending to the east, where the extranuclear [O III] emission, presumably induced by a galactic-scale outflow, is present. The nuclear source is detected by NuSTAR up to the rest-frame 30 keV. The strong, high-ionization Fe K line, first seen by XMM-Newton, and subsequently by Suzaku and Chandra, is not detected in the...

  4. Ultracold Molecular Assembly

    Liu, Lee R.; Zhang, Jessie T.; Yu, Yichao; Hutzler, Nicholas R.; Yu, Liu; Rosenband, Till; Ni, Kang-Kuen
    Chemical reactions can be surprisingly efficient at ultracold temperatures ( < 1mK) due to the wave nature of atoms and molecules. The study of reactions in the ultracold regime is a new research frontier enabled by cooling and trapping techniques developed in atomic and molecular physics. In addition, ultracold molecular gases that offer diverse molecular internal states and large electric dipolar interactions are sought after for studies of strongly interacting many-body quantum physics. Here we propose a new approach for producing ultracold molecules in the absolute internal and motional quantum ground state, where single molecules are assembled one by one...

  5. Radio Frequency Magneto-Optical Trapping of CaF with High Density

    Anderegg, Loic; Augenbraun, Benjamin; Chae, Eunmi; Hemmerling, Boerge; Hutzler, Nicholas R.; Ravi, Aakash; Collopy, Alejandra; Ye, Jun; Ketterle, Wolfgan; Doyle, John
    We demonstrate significantly improved magneto-optical trapping of molecules using a very slow cryogenic beam source and RF modulated and DC magnetic fields. The RF MOT confines 1.1(3)×10^5 CaF molecules at a density of 4(1)×10^6 cm^(−3), which is an order of magnitude greater than previous molecular MOTs. Near Doppler-limited temperatures of 340(20) μK are attained. The achieved density enables future work to directly load optical tweezers and create optical arrays for quantum simulation.

  6. Motional Ground State Cooling Outside the Lamb-Dicke Regime

    Yu, Yichao; Hutzler , Nicholas R.; Zhang, Jessie T.; Liu, Lee R.; Rosenband, Till; Ni, Kang-Kuen
    We report Raman sideband cooling of a single sodium atom to its three-dimensional motional ground state in an optical tweezer. Despite a large Lamb-Dicke parameter, high initial temperature, and large differential light shifts between the excited state and the ground state, we achieve a ground state population of 81(4)% after 100 ms of cooling, for the 85% of atoms that survive cooling and re-imaging. Our technique includes addressing high-order sidebands, where several motional quanta are removed by a single laser pulse, and fast modulation of the optical tweezer intensity. We demonstrate that Raman sideband cooling to the 3D motional ground...

  7. Precision Measurement of Time-Reversal Symmetry Violation with Laser-Cooled Polyatomic Molecules

    Kozyryev, Ivan; Hutzler, Nicholas R.
    Precision searches for time-reversal symmetry violating interactions in polar molecules are extremely sensitive probes of high energy physics beyond the Standard Model. To extend the reach of these probes into the PeV regime, long coherence times and large count rates are necessary. Recent advances in laser cooling of polar molecules offer one important tool -- optical trapping. However, the types of molecules that have been laser-cooled so far do not have the highly desirable combination of features for new physics searches, such as the ability to fully polarize and the existence of internal co-magnetometer states. We show that by utilizing...

  8. The 3d Stress-Tensor Bootstrap

    Dymarsky, Anatoly; Kos, Filip; Kravchuk, Petr; Poland, David; Simmons-Duffin, David
    We study the conformal bootstrap for 4-point functions of stress tensors in parity-preserving 3d CFTs. To set up the bootstrap equations, we analyze the constraints of conformal symmetry, permutation symmetry, and conservation on the stress-tensor 4-point function and identify a non-redundant set of crossing equations. Studying these equations numerically using semidefinite optimization, we compute bounds on the central charge as a function of the independent coefficient in the stress-tensor 3-point function. With no additional assumptions, these bounds numerically reproduce the conformal collider bounds and give a general lower bound on the central charge. We also study the effect of gaps in the scalar, spin-2, and spin-4 spectra on the central...

  9. An equality between entanglement and uncertainty

    Berta, Mario; Coles, Patrick J.; Wehner, Stephanie
    Heisenberg's uncertainty principle implies that if one party (Alice) prepares a system and randomly measures one of two incompatible observables, then another party (Bob) cannot perfectly predict the measurement outcomes. This implication assumes that Bob does not possess an additional system that is entangled to the measured one; indeed the seminal paper of Einstein, Podolsky and Rosen (EPR) showed that maximal entanglement allows Bob to perfectly win this guessing game. Although not in contradiction, the observations made by EPR and Heisenberg illustrate two extreme cases of the interplay between entanglement and uncertainty. On the one hand, no entanglement means that...

  10. Rényi divergences as weighted non-commutative vector valued L_p-spaces

    Berta, Mario; Scholz, Volkher B.; Tomamichel, Marco
    We show that Araki and Masuda's weighted non-commutative vector valued L_p-spaces [Araki & Masuda, Publ. Res. Inst. Math. Sci., 18:339 (1982)] correspond to an algebraic generalization of the sandwiched Rényi divergences with parameter α=p/2. Using complex interpolation theory, we prove various fundamental properties of these divergences in the setup of von Neumann algebras, including a data processing inequality and monotonicity in α. We thereby also give new proofs for the corresponding finite-dimensional properties. We discuss the limiting cases α→{12,1,∞} leading to minus the logarithm of Uhlmann's fidelity, Umegaki's relative entropy, and the max-relative entropy, respectively. As a contribution that might...

  11. Gaussian hypothesis testing and quantum illumination

    Wilde, Mark M.; Tomamichel, Marco; Lloyd, Seth; Berta, Mario
    Quantum hypothesis testing is one of the most basic tasks in quantum information theory and has fundamental links with quantum communication and estimation theory. In this paper, we establish a formula that characterizes the decay rate of the minimal Type-II error probability in a quantum hypothesis test of two Gaussian states given a fixed constraint on the Type-I error probability. This formula is a direct function of the mean vectors and covariance matrices of the quantum Gaussian states in question. We give an application to quantum illumination, which is the task of determining whether there is a low-reflectivity object embedded...

  12. Disentanglement Cost of Quantum States

    Berta, Mario; Majenz, Christian
    We show that the minimal rate of noise needed to catalytically erase the entanglement in a bipartite quantum state is given by the regularized relative entropy of entanglement. This offers a solution to the central open question raised in [Groisman et al., PRA 72, 032317 (2005)] and complements their main result that the minimal rate of noise needed to erase all correlations is given by the quantum mutual information.

  13. Bootstrapping 3D Fermions with Global Symmetries

    Iliesiu, Luca; Kos, Filip; Poland, David; Pufu, Silviu S.; Simmons-Duffin, David
    We study the conformal bootstrap for 4-point functions of fermions ⟨ψ_iψ_jψ_kψ_ℓ⟩ in parity-preserving 3d CFTs, where ψ_i transforms as a vector under an O(N) global symmetry. We compute bounds on scaling dimensions and central charges, finding features in our bounds that appear to coincide with the O(N) symmetric Gross-Neveu-Yukawa fixed points. Our computations are in perfect agreement with the 1/N expansion at large N and allow us to make nontrivial predictions at small N. For values of N for which the Gross-Neveu-Yukawa universality classes are relevant to condensed-matter systems, we compare our results to previous analytic and numerical results.

  14. TASI Lectures on the Conformal Bootstrap

    Simmons-Duffin, David
    These notes are from courses given at TASI and the Advanced Strings School in summer 2015. Starting from principles of quantum field theory and the assumption of a traceless stress tensor, we develop the basics of conformal field theory, including conformal Ward identities, radial quantization, reflection positivity, the operator product expansion, and conformal blocks. We end with an introduction to numerical bootstrap methods, focusing on the 2d and 3d Ising models.

  15. Quark and Lepton Flavor Physics from F-Theory

    Randall, Lisa; Simmons-Duffin, David
    Recent work on local F-theory models shows the potential for new categories of flavor models. In this paper we investigate the perturbative effective theory interpretation of this result. We also show how to extend the model to the neutrino sector.

  16. Radio follow-up of the γ-ray flaring gravitational lens JVAS B0218+357

    Spingola, C.; Dallacasa, D.; Orienti, M.; Giroletti, M.; McKean, J. P.; Cheung, C. C.; Hovatta, T.; Ciprini, S.; D’Ammando, F.; Falco, E.; Larsson, S.; Max-Moerbeck, W.; Ojha, R.; Readhead, A. C. S.; Richards, J. L.; Scargle, J.
    We present results on multifrequency Very Long Baseline Array (VLBA) monitoring observations of the double-image gravitationally lensed blazar JVAS B0218+357. Multi-epoch observations started less than one month after the γ-ray flare detected in 2012 by the Large Area Telescope on board Fermi, and spanned a 2-month interval. The radio light curves did not reveal any significant flux density variability, suggesting that no clear correlation between the high energy and low-energy emission is present. This behaviour was confirmed also by the long-term Owens Valley Radio Observatory monitoring data at 15 GHz. The milliarcsecond-scale resolution provided by the VLBA observations allowed us...

  17. Complex wavefront engineering with disorder-engineered metasurfaces

    Jang, Mooseok; Horie, Yu; Shibukawa, Atsushi; Brake, Joshua; Liu, Yan; Kamali, Seyedeh Mahsa; Arbabi, Amir; Ruan, Haowen; Faraon, Andrei; Yang, Changhuei
    Recently, complex wavefront engineering with disordered media has demonstrated optical manipulation capabilities beyond those of conventional optics. These capabilities include extended volume, aberration-free focusing and subwavelength focusing via evanescent mode coupling. However, translating these capabilities to useful applications has remained challenging as the input-output characteristics of the disordered media (P variables) need to be exhaustively determined via O(P) measurements. Here, we propose a paradigm shift where the disorder is specifically designed so that its exact characteristics are known, resulting in an a priori determined transmission matrix that can be utilized with only a few alignment steps. We implement this concept...

  18. TASI Lectures on Scattering Amplitudes

    Cheung, Clifford
    These lectures are a brief introduction to scattering amplitudes. We begin with a review of basic kinematical concepts like the spinor helicity formalism, followed by a tutorial on bootstrapping tree-level scattering amplitudes. Afterwards, we discuss on-shell recursion relations and soft theorems, emphasizing their broad applicability to gravity, gauge theory, and effective field theories. Lastly, we report on some of the new field theoretic structures which have emerged from the on-shell picture, focusing primarily on color-kinematics duality.

  19. Multiband variability studies and novel broadband SED modeling of Mrk 501 in 2009

    Ahnen, M. L.; Readhead, A. C. S.
    We present an extensive study of the BL Lac object Mrk 501 based on a data set collected during the multi-instrument campaign spanning from 2009 March 15 to 2009 August 1 which includes, among other instruments, MAGIC, VERITAS, Whipple 10-m, Fermi-LAT, RXTE, Swift, GASP-WEBT and VLBA. We find an increase in the fractional variability with energy, while no significant interband correlations of flux changes are found in the acquired data set. The higher variability in the very high energy (>100 GeV, VHE) gamma-ray emission and the lack of correlation with the X-ray emission indicate that the highest-energy electrons that are...

  20. Multiband variability studies and novel broadband SED modeling of Mrk 501 in 2009

    Ahnen, M. L.; Readhead, A. C. S.
    We present an extensive study of the BL Lac object Mrk 501 based on a data set collected during the multi-instrument campaign spanning from 2009 March 15 to 2009 August 1, which includes, among other instruments, MAGIC, VERITAS, Whipple 10 m, and Fermi-LAT to cover the γ-ray range from 0.1 GeV to 20 TeV; RXTE and Swift to cover wavelengths from UV tohard X-rays; and GASP-WEBT, which provides coverage of radio and optical wavelengths. Optical polarization measurements were provided for a fraction of the campaign by the Steward and St. Petersburg observatories. We evaluate the variability of the source and interband...

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