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Caltech Authors (92,131 recursos)
Repository of works by Caltech published authors.

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Mostrando recursos 1 - 20 de 2,505

1. Realizing Exactly Solvable SU(N) Magnets with Thermal Atoms - Beverland, Michael E.; Alagic, Gorjan; Martin, Michael J.; Koller, Andrew P.; Rey, Ana M.; Gorshkov, Alexey V.
We show that n thermal fermionic alkaline-earth atoms in a flat-bottom trap allow one to robustly implement a spin model displaying two symmetries: the Sn symmetry that permutes atoms occupying different vibrational levels of the trap and the SU(N) symmetry associated with N nuclear spin states. The high symmetry makes the model exactly solvable, which, in turn, enables the analytic study of dynamical processes such as spin diffusion in this SU(N) system. We also show how to use this system to generate entangled states that allow for Heisenberg-limited metrology. This highly symmetric spin model should be experimentally realizable even when...

2. Unification of fluctuation theorems and one-shot statistical mechanics - Halpern, Nicole Yunger; Garner, Andrew J. P.; Dahlsten, Oscar C. O.; Vedral, Vlatko
Fluctuation-dissipation relations, such as Crooks' Theorem and Jarzynski's Equality, are powerful tools in quantum and classical nonequilibrium statistical mechanics. We link these relations to a newer approach known as \one-shot statistical mechanics." Rooted in one-shot information theory, one-shot statistical mechanics concerns statements true of every implementation of a protocol, not only of averages. We show that two general models for work extraction in the presence of heat baths obey fluctuation relations and one-shot results. We demonstrate the usefulness of this bridge between frameworks in several ways. Using Crooks' Theorem, we derive a bound on one-shot work quantities. These bounds are...

3. NuSTAR Discovery of a Cyclotron Line in the Be/X-ray Binary RX J0520.5-6932 During Outburst - Tendulkar, Shriharsh P.; Fürst, Felix; Pottschmidt, Katja; Bachetti, Matteo; Bhalerao, Varun B.; Boggs, Steven E.; Christensen, Finn E.; Craig, William W.; Hailey, Charles A.; Harrison, Fiona A.; Stern, Daniel; Tomsick, John A.; Walton, Dominic J.; Zhang, William
We present spectral and timing analysis of NuSTAR observations of RX J0520.5−6932 in the 3-79 keV band collected during its outburst in January 2014. The target was observed on two epochs and we report the detection of a cyclotron resonant scattering feature with central energies of E_(CRSF)=31.3^(+0.8)_(−0.7) keV and 31.5^(+0.7)_(−0.6) keV during the two observations, respectively, corresponding to a magnetic field of B≈2×10^(12) G. The 3-79 keV luminosity of the system during the two epochs assuming a nominal distance of 50 kpc was 3.667±0.007×10^(38)ergs^(−1) and 3.983±0.007×10^(38)ergs^(−1). Both values are much higher than the critical luminosity of ≈1.5×10^(37)ergs^(−1) above which a...

4. Duality invariance of s ≥ 3/2 fermions in AdS - Deser, S.; Seminara, D.
We show that in D=4 AdS, $s\ge 3/2$ partially massless (PM) fermions retain the duality invariances of their flat space massless counterparts. They have tuned ratios m^2/M^2 ≠ 0 that turn them into sums of effectively massless unconstrained helicity ± (s,...,3/2) excitations, shorn of the lowest (non-dual)\helicity ±1/2-rung and -more generally- of succeeding higher rung as well. Each helicity mode is separately duality invariant, like its flat space counterpart.

5. Quiver Tails and N=1 SCFTs from M5-branes - Agarwal, Prarit; Bah, Ibrahima; Maruyoshi, Kazunobu; Song, Jaewon
We study a class of four-dimensional N=1 superconformal field theories obtained by wrapping M5-branes on a Riemann surface with punctures. We identify UV descriptions of four-dimensional SCFTs corresponding to curves with a class of punctures. The quiver tails appearing in these UV descriptions differ significantly from their N=2 counterpart. We find a new type of object that we call the `Fan'. We show how to construct new N=1 superconformal theories using the Fan. Various dual descriptions for these SCFTs can be identified with different colored pair-of-pants decompositions. For example, we find an N=1 analog of Argyres-Seiberg duality for the SU(N) SQCD with 2N flavors. We also compute anomaly coefficients...

6. Planck intermediate results. XXX. The angular power spectrum of polarized dust emission at intermediate and high Galactic latitudes - Adam, R.; Doré, O.; Helou, G.; Pearson, T. J.; Rocha, G.; Chary, R.-R.; Paladini, R.; Rusholme, B.
The polarized thermal emission from diffuse Galactic dust is the main foreground present in measurements of the polarization of the cosmic microwave background (CMB) at frequencies above 100 GHz. In this paper we exploit the uniqueness of the Planck HFI polarization data from 100 to 353 GHz to measure the polarized dust angular power spectra C^(EE)_ℓ and C^(BB)_ℓ over the multipole range 40 < ℓ < 600 well away from the Galactic plane. These measurements will bring new insights into interstellar dust physics and allow a precise determination of the level of contamination for CMB polarization experiments. Despite the non-Gaussian and anisotropic nature of...

7. Hot-swapping robot task goals in reactive formal synthesis - Livingston, Scott C.; Murray, Richard M.
We consider the problem of synthesizing robot controllers to realize a task that unpredictably changes with time. Tasks are formally expressed in the GR(1) fragment of temporal logic, in which some of the variables are set by an adversary. The task changes by the addition or removal of goals, which occurs online (i.e., at run-time). We present an algorithm for mending control strategies to realize tasks after the addition of goals, while avoiding global re-synthesis of the strategy. Experiments are presented for a planar surveillance task in which new regions of interest are incrementally added. Run-times are empirically shown to be favorable compared to re-synthesizing...

8. Geometric Langlands in prime characteristic - Chen, Tsao-Hsien; Zhu, Xinwen
Let $G$ be a semisimple algebraic group over an algebraically closed field $k$, whose characteristic is positive and does not divide the order of the Weyl group of $G$, and let $\breve G$ be its Langlands dual group over $k$. Let $C$ be a smooth projective curve over $k$. Denote by $\Bun_G$ the moduli stack of $G$-bundles on $C$ and $ \Loc_{\breve G}$ the moduli stack of $\breve G$-local systems on $C$. Let $D_{\Bun_G}$ be the sheaf of crystalline differential operators on $\Bun_G$. In this paper we construct an equivalence between the bounded derived category $D^b(\on{QCoh}(\Loc_{\breve G}^0))$ of quasi-coherent sheaves on some open subset $\Loc_{\breve G}^0\subset\Loc_{\breve G}$ and bounded...

9. The two-dimensional Contou-Carrère symbol and reciprocity laws - Osipov, Denis; Zhu, Xinwen
We define a two-dimensional Contou-Carrère symbol, which is a deformation of the two-dimensional tame symbol and is a natural generalization of the (usual) one-dimensional Contou-Carrère symbol. We give several constructions of this symbol and investigate its properties. Using higher categorical methods, we prove reciprocity laws on algebraic surfaces for this symbol. We relate also the two-dimensional Contou-Carrère symbol with the two-dimensional class field theory.

10. Period Integrals and the Riemann-Hilbert Correspondence - Huang, An; Lian, Bong H.; Zhu, Xinwen
A tautological system, introduced in [16][17], arises as a regular holonomic system of partial differential equations that govern the period integrals of a family of complete intersections in a complex manifold X, equipped with a suitable Lie group action. A geometric formula for the holonomic rank of such a system was conjectured in [4], and was verified for the case of projective homogeneous space under an assumption. In this paper, we prove this conjecture in full generality. By means of the Riemann-Hilbert correspondence and Fourier transforms, we also generalize the rank formula to an arbitrary projective manifold with a group action.

11. Frenkel-Gross' irregular connection and Heinloth-Ngô-Yun's are the same - Zhu, Xinwen
We show that the irregular connection on G_m constructed by Frenkel-Gross (2009) and the one constructed by Heinloth-Ngô-Yun (arXiv:1005.2765) are the same, which confirms the Conjecture 2.14 of arXiv:1005.2765. The proof is simple, modulo the big machinery of quantization of Hitchin’s integrable systems as developed by Beilinson-Drinfeld ([BD]). The idea is as follows. Let E be the irregular connection on G_m as constructed by Frenkel-Gross. It admits a natural oper form. We apply the machinery of Beilinson-Drinfeld to produce an automorphic D-module on the corresponding moduli space of G-bundles, with Hecke eigenvalue E. We show that this automorphic D-module is equivariant with respect to the...

12. The Geometric Satake Correspondence for Ramified Groups - Zhu, Xinwen
We prove the geometrical Satake isomorphism for a reductive group defined over F=k((t)), and split over a tamely ramified extension. As an application, we give a description of the nearby cycles on certain Shimura varieties via the Rapoport-Zink-Pappas local models.

13. An example of the derived geometrical Satake correspondence over integers - Zhu, Xinwen
Let G^v be a complex simple algebraic group. We describe certain morphisms of G^v (O)-equivariant complexes of sheaves on the affine Grassmannian Gr of G^v in terms of certain morphisms of G-equivariant coherent sheaves on g, where G is the Langlands dual group of G^v and g is its Lie algebra. This can be regarded as an example of the derived Satake correspondence.

14. The 2-group of linear auto-equivalences of an abelian category and its Lie 2-algebra - Zhu, Xinwen
For any abelian category C satsifying (AB5) over a separated, quasi-compact scheme S, we construct a stack of 2-groups GL(C) over the flat site of S. We will give a concrete description of GL(C) when C is the category of quasi-coherent sheaves on a separated, quasi-compact scheme X over S. We will show that the tangent space gl(C) of GL(C) at the origin has a structure as a Lie 2-algebra.

15. Affine Grassmannians and the geometric Satake in mixed characteristic - Zhu, Xinwen
We endow the set of lattices in Q_p^n with a reasonable algebro-geometric structure. As a result, we prove the representability of affine Grassmannians and establish the geometric Satake correspondence in mixed characteristic. We also give an application of our theory to the study of Rapoport-Zink spaces.

16. Non-abelian Hodge theory for algebraic curves in characteristic p - Chen, Tsao-Hsien; Zhu, Xinwen
Let G be a reductive group over an algebraically closed field of positive characteristic. Let C be a smooth projective curve over k. We give a description of the moduli space of flat G-bundles in terms of the moduli space of G-Higgs bundles over the Frobenius twist C' of C. This description can be regarded as the non-abelian Hodge theory for curves in positive characteristic.

17. Recent erosion in the San Gabriel Mountains - Brown, William M., III; Taylor, Brent D.
Recently the Environmental Quality Laboratory at the California Institute of Technology and the Shore Processes Laboratory at Scripps Institution of Oceanography have undertaken a joint project to study the natural sediment budget in coastal southern California. This budget includes inland erosion which under natural conditions provides sand sized material to nourish the beaches along the shoreline. The San Gabriel Mountains near Los Angeles are an important natural source of sand for beach nourishment. However, the intense urbanization along the base of these mountains have required the advent of extensive flood control structures which significantly reduce the natural transport of sediments from...

18. Assessment of alternative ocean sludge disposal practices - Jackson, George; Morgan, James J.; Koh, Robert C. Y.; Brooks, Norman H.

19. Sediment Management for Southern California Mountains, Coastal Plains, and Shoreline - Taylor, Brent D.; Brown, William M.; Brownlie, William R.
The Environmental Quality Laboratory at Caltech and the Shore Processes Laboratory at Scripps Institution of Oceanography have jointly undertaken a study of regional sediment balance problems in coastal southern California (see map in Figure 1). The overall objective in this study is to define specific alternatives in sediment management that may be implemented to alleviate existing sediment imbalance problems (e.g. inland debris disposal, local shoreline erosion) and possible future problems that have not yet manifested themselves. These alternatives will be identified through a consideration of economic, legal, and institutional issues as well as an analysis of governing physical processes and engineering...

20. Equilibrium as a Conceptual Framework for an Integrated, Synergistic Introductory Course in Chemistry and Physics - Luca, Oana R.
Teachers of introductory chemistry face the reality of outdated curricula and decreased student interest. The retention rates of students in the sciences remain troubling and the need to revisit course content and teaching methods has become increasingly apparent. A more general course framework developed on the principles of scientific teaching and active learning with relevant examples will perhaps allow students to embrace both chemistry and physics as relevant and inextricably linked disciplines. The present article proposes an integrated curriculum of chemistry and physics at the introductory level, based on the overarching conceptual framework of equilibrium with a focus on energy,...

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