18 research outputs found
Precursors, Gauge Invariance, and Quantum Error Correction in AdS/CFT
A puzzling aspect of the AdS/CFT correspondence is that a single bulk
operator can be mapped to multiple different boundary operators, or precursors.
By improving upon a recent model of Mintun, Polchinski, and Rosenhaus, we
demonstrate explicitly how this ambiguity arises in a simple model of the field
theory. In particular, we show how gauge invariance in the boundary theory
manifests as a freedom in the smearing function used in the bulk-boundary
mapping, and explicitly show how this freedom can be used to localize the
precursor in different spatial regions. We also show how the ambiguity can be
understood in terms of quantum error correction, by appealing to the
entanglement present in the CFT. The concordance of these two approaches
suggests that gauge invariance and entanglement in the boundary field theory
are intimately connected to the reconstruction of local operators in the dual
spacetime.Comment: 25 pages, 6 figure
Sub-AdS Scale Locality in AdS/CFT
We investigate sub-AdS scale locality in a weakly coupled toy model of the
AdS/CFT correspondence. We find that this simple model has the correct
density of states at low and high energies to be dual to Einstein gravity
coupled to matter in AdS. Bulk correlation functions also have the correct
behavior at leading order in the large expansion, but non-local effects
emerge at order . Our analysis leads to the conjecture that any large
CFT that is modular invariant and has the right low-energy density of
states is dual to a gravitational theory with sub-AdS scale locality.Comment: 19 page
Precursors and BRST Symmetry
In the AdS/CFT correspondence, bulk information appears to be encoded in the
CFT in a redundant way. A local bulk field corresponds to many different
non-local CFT operators (precursors). We recast this ambiguity in the language
of BRST symmetry, and propose that in the large limit, the difference
between two precursors is a BRST exact and ghost-free term. Using the BRST
formalism and working in a simple model with global symmetries, we re-derive a
precursor ambiguity appearing in earlier work. Finally, we show within this
model that this BRST ambiguity has the right number of parameters to explain
the freedom to localize precursors within the boundary of an entanglement wedge
order by order in the large expansion.Comment: 12 page
Vacua and correlators in hyperbolic de Sitter space
We study the power - and bi -spectrum of vacuum fluctuations in a hyperbolic
section of de Sitter space, comparing two states of physical interest: the
Bunch-Davies and hyperbolic vacuum. We introduce a one -parameter family of de
Sitter hyperbolic sections and their natural vacua, and identify a limit in
which it reduces to the planar section and the corresponding Bunch -Davies
vacuum state. Selecting the Bunch -Davies vacuum for a massless scalar field
implies a mixed reduced density matrix in a hyperbolic section of de Sitter
space. We stress that in the Bunch -Davies state the hyperbolic de Sitter
-point correlation functions have to match the planar de Sitter -point
correlation functions. The expressions for the planar and hyperbolic Bunch
-Davies correlation functions only appear different because of the
transformation from planar to hyperbolic coordinates. Initial state induced
deviations from the standard inflationary predictions are instead obtained by
considering the pure hyperbolic vacuum, as we verify explicitly by computing
the power - and bi -spectrum. For the bi -spectrum in the hyperbolic vacuum we
find that the corrections as compared to the standard Bunch -Davies result are
not enhanced in specific momentum configurations and strongly suppressed for
momenta large compared to the hyperbolic curvature scale. We close with some
final remarks, in particular regarding the implications of these results for
more realistic inflationary bubble scenarios.Comment: Added references, removed typos, added author, extensions in first
section and conclusions. 34 pages, 4 figure
Geometry of the infalling causal patch
The firewall paradox states that an observer falling into an old black hole
must see a violation of unitarity, locality, or the equivalence principle.
Motivated by this remarkable conflict, we analyze the causal structure of black
hole spacetimes in order to determine whether all the necessary ingredients for
the paradox fit within a single observer's causal patch. We particularly focus
on the question of whether the interior partner modes of the outgoing Hawking
quanta can, in principle, be measured by an infalling observer. Since the
relevant modes are spread over the entire sphere, we answer a simple
geometrical question: can any observer see an entire sphere behind the horizon?
We find that for all static black holes in 3+1 and higher dimensions, with any
value of the cosmological constant, no single observer can see both the early
Hawking radiation and the interior modes. We present a detailed description of
the causal patch geometry of the Schwarzschild black hole in 3+1 dimensions,
where an infalling observer comes closest to being able to measure the relevant
modes.Comment: 21 pages, 7 figures. Minor edits/reformatting. Consistent with
version published in PR
Casting Shadows on Holographic Reconstruction
In the context of the AdS/CFT correspondence, we study several holographic
probes that relate information about the bulk spacetime to CFT data. The
best-known example is the relation between minimal surfaces in the bulk and
entanglement entropy of a subregion in the CFT. Building on earlier work, we
identify "shadows" in the bulk: regions that are not illuminated by any of the
bulk probes we consider, in the sense that the bulk surfaces do not pass
through these regions. We quantify the size of the shadow in the near horizon
region of a black hole and in the vicinity of a sufficiently dense star. The
existence of shadows motivates further study of the bulk-boundary dictionary in
order to identify CFT quantities that encode information about the shadow
regions in the bulk. We speculate on the interpretation of our results from a
dual field theory perspective.Comment: 42 pages, 38 figure
Anemia prevalence in women of reproductive age in low- and middle-income countries between 2000 and 2018
Anemia is a globally widespread condition in women and is associated with reduced economic productivity and increased mortality worldwide. Here we map annual 2000–2018 geospatial estimates of anemia prevalence in women of reproductive age (15–49 years) across 82 low- and middle-income countries (LMICs), stratify anemia by severity and aggregate results to policy-relevant administrative and national levels. Additionally, we provide subnational disparity analyses to provide a comprehensive overview of anemia prevalence inequalities within these countries and predict progress toward the World Health Organization’s Global Nutrition Target (WHO GNT) to reduce anemia by half by 2030. Our results demonstrate widespread moderate improvements in overall anemia prevalence but identify only three LMICs with a high probability of achieving the WHO GNT by 2030 at a national scale, and no LMIC is expected to achieve the target in all their subnational administrative units. Our maps show where large within-country disparities occur, as well as areas likely to fall short of the WHO GNT, offering precision public health tools so that adequate resource allocation and subsequent interventions can be targeted to the most vulnerable populations.Peer reviewe
Anemia prevalence in women of reproductive age in low- and middle-income countries between 2000 and 2018
Anemia is a globally widespread condition in women and is associated with reduced economic productivity and increased mortality worldwide. Here we map annual 2000–2018 geospatial estimates of anemia prevalence in women of reproductive age (15–49 years) across 82 low- and middle-income countries (LMICs), stratify anemia by severity and aggregate results to policy-relevant administrative and national levels. Additionally, we provide subnational disparity analyses to provide a comprehensive overview of anemia prevalence inequalities within these countries and predict progress toward the World Health Organization’s Global Nutrition Target (WHO GNT) to reduce anemia by half by 2030. Our results demonstrate widespread moderate improvements in overall anemia prevalence but identify only three LMICs with a high probability of achieving the WHO GNT by 2030 at a national scale, and no LMIC is expected to achieve the target in all their subnational administrative units. Our maps show where large within-country disparities occur, as well as areas likely to fall short of the WHO GNT, offering precision public health tools so that adequate resource allocation and subsequent interventions can be targeted to the most vulnerable populations