282 research outputs found
Preprint arXiv: 2106.05044 Submitted on 9 Jun 2021
As is well-known in the context of topological insulators and superconductors, short-range-correlated fermionic pure Gaussian states with fundamental symmetries are systematically classified by the periodic table. We revisit this topic from a quantum-information-inspired operational perspective without referring to any Hamiltonians, and apply the formalism to bosonic Gaussian states as well as (both fermionic and bosonic) locality-preserving unitary Gaussian operations. We find that while bosonic Gaussian states are all trivial, there exist nontrivial bosonic Gaussian operations that cannot be continuously deformed into the identity under the locality and symmetry constraint. Moreover, we unveil unexpectedly complicated relations between fermionic Gaussian states and operations, pointing especially out that some of the former can be disentangled by the latter under the same symmetry constraint, while some cannot. In turn, we find that some topological operations are genuinely dynamical, in the sense that they cannot create any topological states from a trivial one, yet they are not connected to the identity. The notions of disentanglability and genuinely dynamical topology apply equally to generic interacting topological phases and quantum cellular automata
Impossibility of extending the Ghirardi-Rimini-Weber model to relativistic particles
Spontaneous collapse models are proposed modifications to quantum mechanics which aim to solve the measurement problem. In this article, we will consider models which attempt to extend a specific spontaneous collapse model, the Ghirardi-Rimini-Weber model (GRW), to be consistent with special relativity. We will present a condition that a relativistic GRW model must meet for three cases: for a single particle, for N distinguishable particles, and for indistinguishable particles. We will then show that this relativistic condition implies that one can have a relativistic GRW model for a single particles or for distinguishable noninteracting, nonentangled particles but not otherwise
Preprint arXiv: 2210.05389 Submitted on 11 Oct 2022
We consider free fermions living on lattices in arbitrary dimensions, wherehopping amplitudes follow a power-law decay with respect to the distance. Wefocus on the regime where this power is larger than the spatial dimension(i.e., where the single particle energies are guaranteed to be bounded) forwhich we provide a comprehensive series of fundamental constraints on theirequilibrium and nonequilibrium properties. First we derive a Lieb-Robinsonbound which is optimal in the spatial tail. This bound then implies aclustering property with essentially the same power law for the Green'sfunction, whenever its variable lies outside the energy spectrum. The widelybelieved (but yet unproven in this regime) clustering property for theground-state correlation function follows as a corollary among otherimplications. Finally, we discuss the impact of these results on topologicalphases in long-range free-fermion systems: they justify the equivalence betweenHamiltonian and state-based definitions and the extension of the short-rangephase classification to systems with decay power larger than the spatialdimension. Additionally, we argue that all the short-range topological phasesare unified whenever this power is allowed to be smaller
Preprint arXiv: 2204.02923 Submitted on 6 Apr 2022
We present an ansatz for the ground states of the Quantum Sherrington-Kirkpatrick model, a paradigmatic model for quantum spin glasses. Our ansatz, based on the concept of generalized coherent states, very well captures the fundamental aspects of the model, including the ground state energy and the position of the spin glass phase transition. It further enables us to study some previously unexplored features, such as the non-vanishing longitudinal field regime and the entanglement structure of the ground states. We find that the ground state entanglement can be captured by a simple ensemble of weighted graph states with normally distributed phase gates, leading to a volume law entanglement, contrasting with predictions based on entanglement monogamy
Constraining Lyman-alpha spatial offsets at from VANDELS slit spectroscopy
We constrain the distribution of spatially offset Lyman-alpha emission
(Ly) relative to rest-frame ultraviolet emission in high
redshift () Lyman-break galaxies (LBGs) exhibiting Ly emission
from VANDELS, a VLT/VIMOS slit-spectroscopic survey of the CANDELS Ultra Deep
Survey and Chandra Deep Field South fields (
total). Because slit spectroscopy compresses two-dimensional spatial
information into one spatial dimension, we use Bayesian inference to recover
the underlying Ly spatial offset distribution. We model the
distribution using a 2D circular Gaussian, defined by a single parameter
, the standard deviation expressed in polar
coordinates. Over the entire redshift range of our sample (), we find
kpc ( conf.),
corresponding to arcsec at . We also find that
decreases significantly with redshift. Because
Ly spatial offsets can cause slit-losses, the decrease in
with redshift can partially explain the increase
in the fraction of Ly emitters observed in the literature over this
same interval, although uncertainties are still too large to reach a strong
conclusion. If continues to decrease into the
reionization epoch, then the decrease in Ly transmission from galaxies
observed during this epoch might require an even higher neutral hydrogen
fraction than what is currently inferred. Conversely, if spatial offsets
increase with the increasing opacity of the IGM, slit losses may explain some
of the drop in Ly transmission observed at . Spatially resolved
observations of Ly and UV continuum at are needed to settle the
issue.Comment: Submitted to MNRA
Characterization of the distribution of the Lly\alpha emitters in the 53W002 field at z = 2.4
We present the results of our wide-field narrow band imaging of the field
around the radio galaxy 53W002 at z = 2.390 with Subaru/Suprime-Cam. A custom
made filter NB413 centered at 4140 \AA\ with the width of 83 \AA\ is used to
observe the 31' x 24' area around the radio galaxy. We detected 204 Ly\alpha
emitters (LAEs) at z = 2.4 with a rest frame equivalent width larger than 25
\AA\ to the depth of 26 AB mag (in NB413). The entire LAE population in the
53W002 field has an average number density and distributions of equivalent
width and size that are similar to those of other fields at z ~ 2. We identify
a significant high density region (53W002F-HDR) that spreads over ~ 5' x 4'
near 53W002 where the LAE number density is nearly four times as large as the
average of the entire field. Using the probability distribution function of
density fluctuation, we evaluate the rareness probability of the 53W002F-HDR to
be 0.9^{+2.4}_{-0.62}%, which corresponds to a moderately rich structure. No
notable environmental dependency at the comoving scale of 10 Mpc is found for
the distributions of the Ly\alpha equivalent width and luminosity in the field.
We also detected 4 Ly\alpha blobs (LABs), one of which is newly discovered.
They are all found to be located in the rims of high density regions. The
biased location and unique morphologies in Ly\alpha suggest that galaxy
interaction play a key role in their formation.Comment: 26 pages, 12 figure
Gaussian time-dependent variational principle for the Bose-Hubbard model
We systematically extend Bogoliubov theory beyond the mean field
approximation of the Bose-Hubbard model in the superfluid phase. Our approach
is based on the time dependent variational principle applied to the family of
all Gaussian states (i.e. Gaussian TDVP). First, we find the best ground state
approximation within our variational class using imaginary time evolution in
1d, 2d and 3d. We benchmark our results by comparing to Bogoliubov theory and
DMRG in 1d. Second, we compute the approximate 1- and 2-particle excitation
spectrum as eigenvalues of the linearized projected equations of motion
(linearized TDVP). We find the gapless Goldstone mode, a continuum of
2-particle excitations and a doublon mode. We discuss the relation of the gap
between Goldstone mode and 2-particle continuum to the excitation energy of the
Higgs mode. Third, we compute linear response functions for perturbations
describing density variation and lattice modulation and discuss their relations
to experiment. Our methods can be applied to any perturbations that are linear
or quadratic in creation/annihilation operators. Finally, we provide a
comprehensive overview how our results are related to well-known methods, such
as traditional Bogoliubov theory and random phase approximation
MIPS 24 μm observations of the hubble deep field south: probing the IR-radio correlation of galaxies at z > 1
We present MIPS 24 μm observations of the Hubble Deep Field South taken with the Spitzer Space Telescope. The
resulting image is 254 arcmin^2 in size and has a sensitivity ranging between ~12 and ~30 μJy rms, with a median sensitivity of ~20 μJy rms. A total of 495 sources have been cataloged with a signal-to-noise ratio greater than 5σ. The source catalog is presented as well as source counts which have been corrected for completeness and flux
boosting. The IR sources are then combined with MUSYC optical/NIR and ATHDFS radio observations to obtain
redshifts and radio flux densities of the sample.We use the IR/radio flux density ratio (q_(24)) to explore the IR–radio
correlation for this IR sample and find q_(24) = 0.71 ± 0.31 for sources detected in both IR and radio. The results are extended by stacking IR sources not detected in the radio observations and we derive an average q_(24) for redshift bins between 0 1) sources have an average q_(24) ratio which is better fit by local LIRG SEDs rather than local ULIRG SEDs, indicating that high-redshift ULIRGs differ in their IR/radio properties. So, ULIRGs at high-redshift have SEDs different from those found locally. Infrared-faint radio sources are examined, and while nine radio sources do not have an MIPS detection and are therefore radio-loud active galactic nuclei (AGNs), only one radio source has an extreme IRAC 3.6μm to radio flux density ratio indicating it
is a radio-loud AGN at z > 1
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