Bulk Reconstruction Research Articles

Explicit reconstruction of the entanglement wedge

The problem of how the boundary encodes the bulk in AdS/CFT is still a subject of study today. One of the major issues that needs more elucidation is the problem of subregion duality; what information of the bulk a given boundary subregion encodes. Although the proof given by Dong, Harlow, and Wall [14] states that the entanglement wedge of the bulk should be encoded in boundary subregions, no explicit procedure for reconstructing the entanglement wedge was given so far. In this paper, mode sum approach to obtaining smearing functions for a single bulk scalar is generalised to include bulk reconstruction in the entanglement wedge of boundary subregions. It is generally expectated that solutions to the wave equation on a complicated coordinate patch are needed, but this hard problem has been transferred to a less hard but tractable problem of matrix inversion.

Concurrence of bulk and surface order reconstruction to the relaxation of frustrated nematics

Applying appropriate electric pulses to a nematic liquid crystal confined between plates, the bulk order reconstruction can occur, a mechanism allowing the switching between topologically different nematic textures without any director rotation. Using a moving mesh finite element method we describe the order tensor dynamics for a nematic inside an asymmetric n-cell, putting in evidence as textural distortions induced by strong asymmetries can be relaxed via both bulk and surface order reconstruction, occurring close to a confining plate with different time duration.

Tensor networks, $p$-adic fields, and algebraic curves: arithmetic and the $\mathrm{AdS}_3 / \mathrm{CFT}_2$ correspondence

One of the many remarkable properties of conformal field theory in two dimensions is its connection to algebraic geometry. Since every compact Riemann surface is a projective algebraic curve, many constructions of interest in physics (which a priori depend on the analytic structure of the spacetime) can be formulated in purely algebraic language. This opens the door to interesting generalizations, obtained by taking another choice of field: for instance, the p-adics. We generalize the AdS/CFT correspondence according to this principle; the result is a formulation of holography in which the bulk geometry is discrete—the Bruhat–Tits tree for PGL(2,Qp)—but the group of bulk isometries nonetheless agrees with that of boundary conformal transformations and is not broken by discretization. We suggest that this forms the natural geometric setting for tensor networks that have been proposed as models of bulk reconstruction via quantum error correcting codes; in certain cases, geodesics in the Bruhat–Tits tree reproduce those constructed using quantum error correction. Other aspects of holography also hold: Standard holographic results for massive free scalar fields in a fixed background carry over to the tree, whose vertical direction can be interpreted as a renormalization-group scale for modes in the boundary CFT. Higher-genus bulk geometries (the BTZ black hole and its generalizations) can be understood straightforwardly in our setting, and the Ryu–Takayanagi formula for the entanglement entropy appears naturally.

Polypropylene Darning: A New Alternative for Reconstruction of Orbital Floor after Total Maxillectomy.

Removal of orbital floor is an integral part of total (radical) maxillectomy (type IIIa), which if not managed properly, may lead to some eye related distressing complications like diplopia, eyelid malposition, epiphora, dacryocystitis, enopthalmos and ectoprion. Among all, diplopia is the most distressing complication which hampers daily activity. Various options for orbital floor reconstruction are available like titanium sheet, polypropylene mesh, non-vascularized or vascularized bone graft, pedicled flaps, micro-vascular free flaps, prosthesis placement, and split skin graft followed by obturator placement. Till date no-body has tried stabilization of eye ball by 'darning' the orbital floor using non-absorbable suture. 'Polypropylene suture darning' is an easy to learn, novel method with equally good results. Five patients with potentially resectable tumors underwent total maxillectomy. I used polypropylene 3-0 round body suture and 'darning' was done at orbital floor, incorporating periosteum (if remaining) and peri-orbital fat into the sutures. Muscle flaps were done to provide bulk and palatal reconstruction. Assessment of patients was done post-operatively at day-5 i.e., before discharge and at 1month after surgery, and also in further follow up visits. The results were very good in terms of clear vision & eye movements (directly related to 'darning'), and the aesthetic look of patients and bilateral symmetry were satisfactory (not related to darning). Darning of orbital floor by polypropylene after total maxillectomy is an easy to learn and cost-effective method of reconstruction with good results.

Quantum extremal surfaces: holographic entanglement entropy beyond the classical regime

We propose that holographic entanglement entropy can be calculated at arbitrary orders in the bulk Planck constant using the concept of a "quantum extremal surface": a surface which extremizes the generalized entropy, i.e. the sum of area and bulk entanglement entropy. At leading order in bulk quantum corrections, our proposal agrees with the formula of Faulkner, Lewkowycz, and Maldacena, which was derived only at this order; beyond leading order corrections, the two conjectures diverge. Quantum extremal surfaces lie outside the causal domain of influence of the boundary region as well as its complement, and in some spacetimes there are barriers preventing them from entering certain regions. We comment on the implications for bulk reconstruction.

Null geodesics, local CFT operators, and AdS/CFT for subregions

We investigate the nature of the AdS/CFT duality between a subregion of the bulk and its boundary. In global AdS/CFT in the classical G_N=0 limit, the duality reduces to a boundary value problem that can be solved by restricting to one-point functions of local operators in the CFT. We show that the solution of this boundary value problem depends continuously on the CFT data. In contrast, the AdS-Rindler subregion cannot be continuously reconstructed from local CFT data restricted to the associated boundary region. Motivated by related results in the mathematics literature, we posit that a continuous bulk reconstruction is only possible when every null geodesic in a given bulk subregion has an endpoint on the associated boundary subregion. This suggests that a subregion duality for AdS-Rindler, if it exists, must involve nonlocal CFT operators in an essential way.

Spectroscopic Investigation of Iron Substitution in EuCoO3: Related Impact on the Catalytic Properties in the High-Temperature N2O Decomposition

This study is dedicated to a combined spectroscopic approach for investigating bulk versus surface reconstructions that originated during high-temperature catalytic applications on EuCo1–xFexO3 and to their related impact on the catalytic properties. By way of illustration, the decomposition of nitrous oxide (N2O) has been selected as a case study achieved in complex feed gas composition in the presence of NOx and water vapor, which can speed up surface and bulk modifications at 900 °C with related impact on the reactivity of N-containing species. Particular attention was paid to the appearance of Co2+ species in different stages of the preparation, especially after reaction. While XPS cannot discriminate the nature of those species without any ambiguity, the combination of Mössbauer and photoluminescence spectroscopy can help in understanding changes in the local environment of europium, iron, and cobalt. The impact of those surface changes on the kinetic parameters of the decomposition of N2O has been examined.

Prompt reconstruction of LHC collision data with the ATLAS reconstruction software

Since the start of LHC operations in November 2009, the ATLAS detector has recorded many millions of collision events. With the luminosity increasing rapidly in 2010, it is a challenge for the reconstruction and data distribution efforts to provide physics-quality data to analysts around the world within a short timescale. In this note I will describe how a two-pass system, where calibration constants and corrections are calculated on a subset of the data before being used in bulk reconstruction, provides a robust and well-monitored mechanism for meeting these challenges.

Support-Induced Effects of LaFeO3 Perovskite on the Catalytic Performances of Supported Pt Catalysts in DeNOx Applications

A comparative investigation of the catalytic performance in the simultaneous conversion of NOx and N2O has been achieved on supported nanosized Pt particles interacting with conventional alumina and perovskite based materials. Particular attention has been paid to successive thermal treatments under reductive and oxidative atmospheres which induce bulk and surface reconstructions. Those modifications considerably alter the catalytic behavior of Pt in interaction with LaFeO3 or γ-Al2O3 in terms of activity and selectivity toward the selective transformation of NOx to nitrogen at low temperature. Changes in physicochemical properties have been examined using appropriate techniques, such as H2-temperature-programmed reduction (TPR), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and Fourier transform infrared (FTIR) of CO adsorption. It has been found that oxidic Pt4+ species initially stabilized on LaFeO3 lead after subsequent H2 reduction to the formation of metallic nano-Pt particles in stronger interaction than on γ-Al2O3 support and then become more resistant to sintering during thermal aging in 1000 ppm NO, 1000 ppm N2O, 3 vol % O2, 0.5 vol % H2O, and 0.5 vol % H2 at 500 °C. Correlatively, significant improvements have been observed in the selective reduction of NOx to nitrogen. This study opens new prospects in the development of supported catalysts containing low Pt loadings because of the existence of stronger interactions with perovskite supports.

Ceria–zirconia mixed oxides as thermal resistant catalysts for the decomposition of nitrous oxide at high temperature

This present study deals with the development of thermally stable catalysts for the decomposition of nitrous oxide. There is actually a growing interest to minimise the emissions of nitrous oxide (N 2O) as side-product from nitric acid plants due to a global warming potential of approximately 300 times higher than that of CO 2. Different strategies have already been implemented at industrial scale but they are still suffering from significant drawbacks essentially associated to a poor selectivity and sometimes a short lifetime in particular when the catalytic process is inserted downstream the ammonia burner. In those critical conditions, with high residual temperature of ∼900 °C, significant surface and bulk reconstructions take place and then lead to drastic losses of specific surface area and related catalytic performances in the decomposition of N 2O to N 2. Previous investigations performed in our laboratory revealed the potentiality of zirconia particularly after yttria incorporation [Appl. Catal. B 62 (2005) 236]. Novel developments of more stable ceria–zirconia based catalysts are reported in this study. Further stabilisation and enhancement in activity have been discussed on the basis of oxygen mobility related to structural properties.

Impact of Thermal Aging on the Kinetic Parameters of the NO/H2 Reaction on Pd/LaCoO3

This paper deals with the kinetics of the reduction of NO by H(2) on Pd supported over reducible supports, such as LaCoO(3). An extensive kinetic investigation was performed on aged catalysts after exposure to successive reductive and oxidative atmospheres at a high temperature (T = 500 degrees C). Typically, Pd/LaCoO(3) was reduced in pure H(2) and then aged under reactive conditions in the presence of an excess of O(2). Both thermal treatments are accompanied by significant bulk and surface reconstructions characterized by X-ray diffraction and X-ray photoelectron spectroscopy. Pd/LaCoO(3) is extensively reducef to Pd(0)/CoO(x)/La(2)O(3) after H(2) exposure. It was previously found that the NO/H(2) reaction on Pd(0)/CoO(x)/La(2)O(3) involved the Pd/support interface. This study reports that subsequent thermal aging under oxidative conditions leads to the restoration of the perovskite structure with parallel changes in the chemical environment of oxidic palladium species. The NO reduction by hydrogen was used as a probe reaction to investigate related modifications of the surface properties. It was found that significant changes in the kinetic features of Pd/LaCoO(3) occur after thermal aging, compared to the prereduced catalyst, because of surface modifications that might alter the adsorptive properties of Pd and more significantly the nature of the dissociation step of NO. These surface modifications induce a selectivity enhancement to the formation of nitrogen.

Use of the latissimus dorsi flap for recontouring and augmentation after TRAM flap breast reconstruction.

The transverse rectus abdominis musculocutaneous (TRAM) flap is the most commonly used autogenous tissue flap for breast reconstruction. However, it may not provide sufficient volume in all patients to match the contralateral breast. Insufficient abdominal bulk or bilateral reconstructions limit the amount of tissue available for the TRAM flap. Partial flap loss from fat necrosis or radiation injury may result in contour deformities of the reconstructed breast. Additional soft-tissue augmentation and contouring may be necessary to produce adequate volume, contour, and symmetry. The authors present 7 patients who underwent latissimus dorsi flap reconstruction to correct volume and contour abnormalities that developed after TRAM flap breast reconstruction. Preservation of the serratus branch of the thoracodorsal vessels allows this flap to be used even after free TRAM flap reconstruction.

Pectoralis major musculocutaneous flap: A new flap in head and neck reconstruction

The pectoralis major musculocutaneous flap described by Ariyan has great potential in single stage reconstructions of the head and neck. The advantages of the flap are greater length, improved vascularity, bulk, and one-stage reconstruction of oropharyngeal defects. The flap was used successfully in eight patients to reconstruct large defects in the head and neck area. Experience to date indicates that this flap has greater versatility than the deltopectoral flap in one-stage head and neck reconstructions.