Lattice Models for Granular-Like Velocity Fields: Hydrodynamic Description

AbstractTopological materials exhibit edge-localized scattering-free modes protected by their nontrivial bulk topology through the bulk-edge correspondence in Hermitian systems. While topological phenomena have recently been much investigated in non-Hermitian systems with dissipations and injections, the fundamental principle of their edge modes has not fully been established. Here, we reveal that, in non-Hermitian systems, robust gapless edge modes can ubiquitously appear owing to a mechanism that is distinct from bulk topology, thus indicating the breakdown of the bulk-edge correspondence. The robustness of these edge modes originates from yet another topological structure accompanying the branchpoint singularity around an exceptional point, at which eigenvectors coalesce and the Hamiltonian becomes nondiagonalizable. Their characteristic complex eigenenergy spectra are applicable to realize lasing wave packets that propagate along the edge of the sample. We numerically confirm the emergence and the robustness of the proposed edge modes in the prototypical lattice models. Furthermore, we show that these edge modes appear in a model of chiral active matter based on the hydrodynamic description, demonstrating that active matter can exhibit an inherently non-Hermitian topological feature. The proposed general mechanism would serve as an alternative designing principle to realize scattering-free edge current in non-Hermitian devices, going beyond the existing frameworks of non-Hermitian topological phases.

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Lattice models for granular-like velocity fields: finite-size effects

Journal of Statistical Mechanics Theory and Experiment ◽

10.1088/1742-5468/2016/09/093203 ◽

2016 ◽

Vol 2016 (9) ◽

pp. 093203 ◽

Cited By ~ 10

Author(s):

C A Plata ◽

A Manacorda ◽

A Lasanta ◽

A Puglisi ◽

A Prados

Keyword(s):

Size Effects ◽

Finite Size ◽

Lattice Models ◽

Velocity Fields ◽

Finite Size Effects

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C. The Continuous Spectrum of Pulsating Variable Stars

Symposium - International Astronomical Union ◽

10.1017/s007418090001901x ◽

1967 ◽

Vol 28 ◽

pp. 177-206

Author(s):

J. B. Oke ◽

C. A. Whitney

Keyword(s):

Continuous Spectrum ◽

Variable Stars ◽

Velocity Fields ◽

The Other ◽

Line Spectrum ◽

Direct Information ◽

Thermodynamic Structure ◽

Diagnostic Interpretation ◽

Pulsating Variable Stars ◽

The Continuum

Pecker:The topic to be considered today is the continuous spectrum of certain stars, whose variability we attribute to a pulsation of some part of their structure. Obviously, this continuous spectrum provides a test of the pulsation theory to the extent that the continuum is completely and accurately observed and that we can analyse it to infer the structure of the star producing it. The continuum is one of the two possible spectral observations; the other is the line spectrum. It is obvious that from studies of the continuum alone, we obtain no direct information on the velocity fields in the star. We obtain information only on the thermodynamic structure of the photospheric layers of these stars–the photospheric layers being defined as those from which the observed continuum directly arises. So the problems arising in a study of the continuum are of two general kinds: completeness of observation, and adequacy of diagnostic interpretation. I will make a few comments on these, then turn the meeting over to Oke and Whitney.

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The Interpretation of Line Profiles

International Astronomical Union Colloquium ◽

10.1017/s0252921100053318 ◽

1977 ◽

Vol 36 ◽

pp. 191-215

Author(s):

G.B. Rybicki

Keyword(s):

Magnetic Fields ◽

Atomic Physics ◽

Velocity Fields ◽

Spectral Lines ◽

Inhomogeneous Structure ◽

The Sun ◽

Line Profiles ◽

Physical Phenomena

Observations of the shapes and intensities of spectral lines provide a bounty of information about the outer layers of the sun. In order to utilize this information, however, one is faced with a seemingly monumental task. The sun’s chromosphere and corona are extremely complex, and the underlying physical phenomena are far from being understood. Velocity fields, magnetic fields, Inhomogeneous structure, hydromagnetic phenomena – these are some of the complications that must be faced. Other uncertainties involve the atomic physics upon which all of the deductions depend.

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Series Expansion Methods for Strongly Interacting Lattice Models

10.1017/cbo9780511584398 ◽

2006 ◽

Cited By ~ 160

Author(s):

Jaan Oitmaa ◽

Chris Hamer ◽

Weihong Zheng

Keyword(s):

Series Expansion ◽

Lattice Models ◽

Strongly Interacting

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Central kiloparsec of NGC 1326 observed with SINFONI

Astronomy and Astrophysics ◽

10.1051/0004-6361/201936451 ◽

2020 ◽

Vol 638 ◽

pp. A53

Author(s):

Nastaran Fazeli ◽

Gerold Busch ◽

Andreas Eckart ◽

Françoise Combes ◽

Persis Misquitta ◽

...

Keyword(s):

Black Hole ◽

Galaxy Evolution ◽

Near Infrared ◽

Velocity Fields ◽

Molecular Gas ◽

Nearby Galaxy ◽

Stellar Content ◽

Stellar Rotation ◽

Supermassive Black Hole ◽

Integral Field Spectrograph

Gas inflow processes in the vicinity of galactic nuclei play a crucial role in galaxy evolution and supermassive black hole growth. Exploring the central kiloparsec of galaxies is essential to shed more light on this subject. We present near-infrared H- and K-band results of the nuclear region of the nearby galaxy NGC 1326, observed with the integral-field spectrograph SINFONI mounted on the Very Large Telescope. The field of view covers 9″ × 9″ (650 × 650 pc2). Our work is concentrated on excitation conditions, morphology, and stellar content. The nucleus of NGC 1326 was classified as a LINER, however in our data we observed an absence of ionised gas emission in the central r ∼ 3″. We studied the morphology by analysing the distribution of ionised and molecular gas, and thereby detected an elliptically shaped, circum-nuclear star-forming ring at a mean radius of 300 pc. We estimate the starburst regions in the ring to be young with dominating ages of < 10 Myr. The molecular gas distribution also reveals an elongated east to west central structure about 3″ in radius, where gas is excited by slow or mild shock mechanisms. We calculate the ionised gas mass of 8 × 105 M⊙ completely concentrated in the nuclear ring and the warm molecular gas mass of 187 M⊙, from which half is concentrated in the ring and the other half in the elongated central structure. The stellar velocity fields show pure rotation in the plane of the galaxy. The gas velocity fields show similar rotation in the ring, but in the central elongated H2 structure they show much higher amplitudes and indications of further deviation from the stellar rotation in the central 1″ aperture. We suggest that the central 6″ elongated H2 structure might be a fast-rotating central disc. The CO(3–2) emission observations with the Atacama Large Millimeter/submillimeter Array reveal a central 1″ torus. In the central 1″ of the H2 velocity field and residual maps, we find indications for a further decoupled structure closer to a nuclear disc, which could be identified with the torus surrounding the supermassive black hole.

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