2,765 research outputs found
Black Hole Statistics from Holography
We study the microstates of the ``small'' black hole in the \half-BPS
sector of AdS, the superstar of Myers and Tafjord, using the
powerful holographic description provided by LLM. The system demonstrates the
inherently statistical nature of black holes, with the geometry of Myer and
Tafjord emerging only after averaging over an ensemble of geometries. The
individual microstate geometries differ in the highly non-trivial topology of a
quantum foam at their core, and the entropy can be understood as a partition of
units of flux among 5-cycles, as required by flux quantization. While the
system offers confirmation of the most controversial aspect of Mathur and
Lunin's recent ``fuzzball'' proposal, we see signs of a discrepancy in
interpreting its details.Comment: 21 pages, 4 figures; References adde
Complex Matrix Model and Fermion Phase Space for Bubbling AdS Geometries
We study a relation between droplet configurations in the bubbling AdS
geometries and a complex matrix model that describes the dynamics of a class of
chiral primary operators in dual N=4 super Yang Mills (SYM). We show rigorously
that a singlet holomorphic sector of the complex matrix model is equivalent to
a holomorphic part of two-dimensional free fermions, and establish an exact
correspondence between the singlet holomorphic sector of the complex matrix
model and one-dimensional free fermions. Based on this correspondence, we find
a relation of the singlet holomorphic operators of the complex matrix model to
the Wigner phase space distribution. By using this relation and the AdS/CFT
duality, we give a further evidence that the droplets in the bubbling AdS
geometries are identified with those in the phase space of the one-dimensional
fermions. We also show that the above correspondence actually maps the
operators of N=4 SYM corresponding to the (dual) giant gravitons to the droplet
configurations proposed in the literature.Comment: 27 pages, 6 figures, some clarification, typos corrected, published
versio
Rational foundation of GR in terms of statistical mechanic in the AdS/CFT framework
In this article, we work out the microscopic statistical foundation of the
supergravity description of the simplest 1/2 BPS sector in the AdS(5)/CFT(4).
Then, all the corresponding supergravity observables are related to
thermodynamical observables, and General Relativity is understood as a
mean-field theory. In particular, and as an example, the Superstar is studied
and its thermodynamical properties clarified.Comment: 13 pages, 6 eps figures, latex, some improvements introduced,
reference added, typos correcte
Effect of Finite Granularity of Detectors on Anisotropy Coefficients
The coefficients that describe the anisotropy in the azimuthal distribution
of particles are lower when the particles are recorded in a detector with
finite granularity and measures only hits. This arises due to loss of
information because of multiple hits in any channel. The magnitude of this loss
of signal depends both on the occupancy and on the value of the coefficient.
These correction factors are obtained for analysis methods differing in detail,
and are found to be different.Comment: 11 pages including 2 figure
Semi-classical Probe Strings on Giant Gravitons Backgrounds
In the first part of this paper we study two symmetries of the LLM
metric, both of which exchange black and white regions. One of them which can
be interpreted as the particle-hole symmetry is the symmetry of the whole
supergravity solution while the second one is just the symmetry of the metric
and changes the sign of the fivefrom flux. In the second part of the paper we
use closed string probes and their semi-classical analysis to compare the two
1/2 BPS deformations of , the smooth LLM geometry which
contains localized giant gravitons and the superstar case which is a solution
with naked singularity corresponding to smeared giants. We discuss the
realization of the symmetry in the semi-classical closed string probes
point of view.Comment: 29 pages, 6 .eps figures; v2: References adde
Bosonization of non-relativstic fermions in 2-dimensions and collective field theory
We revisit bosonization of non-relativistic fermions in one space dimension.
Our motivation is the recent work on bubbling half-BPS geometries by Lin, Lunin
and Maldacena (hep-th/0409174). After reviewing earlier work on exact
bosonization in terms of a noncommutative theory, we derive an action for the
collective field which lives on the droplet boundaries in the classical limit.
Our action is manifestly invariant under time-dependent reparametrizations of
the boundary. We show that, in an appropriate gauge, the classical collective
field equations imply that each point on the boundary satisfies Hamilton's
equations for a classical particle in the appropriate potential. For the
harmonic oscillator potential, a straightforward quantization of this action
can be carried out exactly for any boundary profile. For a finite number of
fermions, the quantum collective field theory does not reproduce the results of
the exact noncommutative bosonization, while the latter are in complete
agreement with the results computed directly in the fermi theory.Comment: references added and typos corrected; 21 pages, 3 figures, eps
The M2/M5 BPS Partition Functions from Supergravity
In the framework of the AdS/CFT duality, we calculate the supersymmetric
partition function of the superconformal field theories living in the world
volume of either -branes or -branes. We used the dual
supergravity partition function in a saddle point approximation over
supersymmetric Black Holes. Since our BHs are written in asymptotically global
co-ordinates, the dual SCFTs are in for . The
resulting partition function shows phase transitions, constraints on the phase
space and allowed us to identify unstable BPS Black hole in the phase.
These configurations should correspond to unstable configurations in the dual
theory. We also report an intriguing relation between the most general Witten
Index, computed in the above theories, and our BPS partition functions.Comment: 9 pages, 2 columns, 4 figures, revtex, typos corrected, reference
adde
Delivery time dynamics in an assemble-to-order inventory and order based production control system
System dynamics play a critical role in influencing supply chain performance. However, the dynamic property of the assemble-to-order (ATO) system remain unexplored. Based on control theory, the inventory and order based production control system (IOBPCS) family, can be utilized as a base framework for assessing system dynamics. However, the underlying assumption in traditional IOBPCS-based analytical studies is that the system is linear and the delivery time to end customers is negligible or backlog is used as a surrogate indicator. Our aim is to incorporate customer delivery lead-time variance as the third assessment measure alongside capacity availability and inventory variance as part of the so-called ‘performance triangle’– capacity at the supplier, the customer order decoupling point (CODP) inventory and the delivery lead-time. Using the ‘performance triangle’ and adopting non-linear control engineering techniques, we assess the dynamic behaviour of an ATO system in the electronics sector. We benchmark the ATO system dynamics model against the IOBPCS family. We exploit frequency response analysis to ensure a robust system design by considering three measures of the ‘performance triangle’. The findings suggest delivery LT variance can be minimised by maintaining the ATO system as a true Push-Pull hybrid state with sufficient CODP stock, although increased operational cost driven by bullwhip and CODP variance need to be considered. However, if the hybrid ATO system 'switches' to the pure Push state, the mean and variance of delivery LT can be significantly increased
Modeliranje, upravljanje i eksperimentalno istraživanje novoga raspodijeljenog statičkog kompenzatora jalove snage zasnovanog na višestupanjskom pretvaraču s ulančenim H-mostovima
A novel static synchronous compensator for reactive power compensation of distribution system (DSTATCOM) is proposed, based on the cascaded H-bridge multilevel inverter configuration. The mathematical formulation of the multilevel DSTATCOM is presented using state-space representations. A new software phase-locked loop (SPLL) is presented for grid synchronization and the obtained phase angle of the fundamental component of the grid voltage is utilized for deriving the active and reactive power balancing equations of the multilevel DSTATCOM. The proportional-resonant (PR) controller scheme is adopted for the current tracking control of the inverter, and the average dc-link voltage is controlled using a proportional-integral (PI) controller to regulate the active power flow of the DSTATCOM. Besides, the voltage balancing (VB) control among individual H-bridges is achieved by using separate PI regulators to control the difference voltage between the individual dc-link voltage and the average dc-link voltage. The validity of the proposed multilevel DSTATCOM and its control strategies is substantially confirmed by the extensive simulation results and the experimental results from the prototype system.Predložen je novi statički sinkroni kompenzator za kompenzaciju jalove snage distribucijskog sustava (DSTATCOM) zasnovan na konfiguraciji višestupanjskog pretvarača s ulančenim H-mostovima. Matematički model višerazinskog DSTATCOM-a prikazan je u prostoru stanja. Predstavljena je nova programski izvedena petlja sa zaključanom fazom namijenjena sinkronizaciji s mrežom, a dobiveni fazni kut osnovne komponente mrežnog napona koristi se za izvod jednadžbi ravnoteže aktivne i jalove snage višerazinskog DSTATCOM-a. Usvojen je koncept proporcionalno-rezonantnog regulatora za slijeđenje trajektorije struje pretvarača, a srednji napon istosmjernog međukruga upravlja se korištenjem proporcionalno-integracijskog (PI) regulatora u svrhu regulacije toka radne snage DSTATCOM-a. Osim toga, upravljanje uravnoteženjem napona među pojedinim H-mostovima ostvareno je korištenjem odvojenih PI regulatora za upravljanje razlikom napona među pojedinim istosmjernim međukrugovima te srednjim naponom istosmjernih međukrugova. Valjanost predloženog višestupanjskog DSTATCOM-a i primijenjenih upravljačkih strategija potvrđena je brojnim simulacijskim i eksperimentalnim rezultatima na prototipskoj izvedbi ovog sustava
Extended Fermion Representation of Multi-Charge 1/2-BPS Operators in AdS/CFT -- Towards Field Theory of D-Branes --
We extend the fermion representation of single-charge 1/2-BPS operators in
the four-dimensional N=4 super Yang-Mills theory to general (multi-charge)
1/2-BPS operators such that all six directions of scalar fields play roles on
an equal footing. This enables us to construct a field-theorectic
representation for a second-quantized system of spherical D3-branes in the
1/2-BPS sector. The Fock space of D3-branes is characterized by a novel
exclusion principle (called `Dexclusion' principle), and also by a nonlocality
which is consistent with the spacetime uncertainty relation. The Dexclusion
principle is realized by composites of two operators, obeying the usual
canonical anticommutation relation and the Cuntz algebra, respectively. The
nonlocality appears as a consequence of a superselction rule associated with a
symmetry which is related to the scale invariance of the super Yang-Mills
theory. The entropy of the so-called superstars, with multiple charges, which
have been proposed to be geometries corresponding to the condensation of giant
gravitons is discussed from our viewpoint and is argued to be consistent with
the Dexclusion principle. Our construction may be regarded as a first step
towards a possible new framework of general D-brane field theory.Comment: 43 pages, 4 figures; version 2, corrected typos and added reference
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