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Articles 1 - 17 of 17

Full-Text Articles in Physics

Black Hole Thermalization, D0 Brane Dynamics, And Emergent Spacetime, Paul L. Riggins '12, Vatche Sahakian Aug 2012

Black Hole Thermalization, D0 Brane Dynamics, And Emergent Spacetime, Paul L. Riggins '12, Vatche Sahakian

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When matter falls past the horizon of a large black hole, the expectation from string theory is that the configuration thermalizes and the information in the probe is rather quickly scrambled away. The traditional view of a classical unique spacetime near a black hole horizon conflicts with this picture. The question then arises as to what spacetime does the probe actually see as it crosses a horizon, and how does the background geometry imprint its signature onto the thermal properties of the probe. In this work, we explore these questions through an extensive series of numerical simulations of D0 branes ...


From Surface Operators To Non-Abelian Volume Operators In Puff Field Theory, Vatche Sahakian Jun 2010

From Surface Operators To Non-Abelian Volume Operators In Puff Field Theory, Vatche Sahakian

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Puff field theory (PFT) is a low energy decoupling regime of string theory that still retains the nonlocal attributes of the parent theory—while preserving isotropy for its nonlocal degrees of freedom. It realizes an extended holographic dictionary at strong coupling and dynamical nonlocal states akin to defects or the surface operators of local gauge theories. In this work, we probe the nonlocal features of PFT using D3 branes. We find supersymmetric configurations that end on defects endowed with non-Abelian degrees of freedom. These are 2+1 dimensional defects in the 3+1 dimensional PFT that may be viewed as ...


New Mechanism For Nonlocality From String Theory: Uv-Ir Quantum Entanglement And Its Imprints On The Cmb, Gregory Minton '08, Vatche Sahakian Jan 2008

New Mechanism For Nonlocality From String Theory: Uv-Ir Quantum Entanglement And Its Imprints On The Cmb, Gregory Minton '08, Vatche Sahakian

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Puff field theories (PFT) arise as the decoupling limits of D3 branes in a Melvin universe and exhibit spatially nonlocal dynamics. Unlike other realizations of nonlocality in string theory, PFTs have full SO(3) rotational symmetry. In this work, we analyze the strongly coupled regime of a PFT through gravitational holography. We find a novel mechanism at the heart of the phenomenon of nonlocality: a quantum entanglement of UV and IR dynamics. In the holographic bulk, this translates to an apparent horizon splitting the space into two regions—with the UV completion of the PFT sitting at the horizon. We ...


Emergence Of The Fuzzy Horizon Through Gravitational Collapse, Anand Murugan '07, Vatche Sahakian Nov 2006

Emergence Of The Fuzzy Horizon Through Gravitational Collapse, Anand Murugan '07, Vatche Sahakian

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For a large enough Schwarzschild black hole, the horizon is a region of space where gravitational forces are weak; yet it is also a region leading to numerous puzzles connected to stringy physics. In this work, we analyze the process of gravitational collapse and black hole formation in the context of light-cone M-theory. We find that, as a shell of matter contracts and is about to reveal a black hole horizon, it undergoes a thermodynamic phase transition. This involves the binding of D0 branes into D2’s, and the new phase leads to large membranes of the size of the ...


Hairy Strings, Vatche Sahakian Jan 2006

Hairy Strings, Vatche Sahakian

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Zero modes of the world-sheet spinors of a closed string can source higher order moments of the bulk supergravity fields. In this work, we analyze various configurations of closed strings focusing on the imprints of the quantized spinor vacuum expectation values onto the tails of bulk fields. We identify supersymmetric arrangements for which all multipole charges vanish; while for others, we find that one is left with Neveu-Schwarz–Neveu-Schwarz, and Ramond-Ramond dipole and quadrupole moments. Our analysis is exhaustive with respect to all the bosonic fields of the bulk and to all higher order moments. We comment on the relevance ...


On The Polarization Of Closed Strings By Ramond-Ramond Fluxes, Vatche Sahakian Oct 2004

On The Polarization Of Closed Strings By Ramond-Ramond Fluxes, Vatche Sahakian

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In the Green-Schwarz formalism, the closed string worldsheet of the IIB theory couples to Ramond-Ramond (RR) fluxes through spinor bilinears. We study the effect of such fluxes by analyzing the supersymmetry transformation of the worldsheet in general backgrounds. We show that, in the presence RR fields, the closed string can get `polarized', as the spinors acquire non-zero vevs in directions correlating with the orientation of close-by D-branes. Reversing the argument, this may allow for worldsheet configurations—with non-trivial spinor structure—that source RR moments.


Closed Strings In Ramond-Ramond Backgrounds, Vatche Sahakian Apr 2004

Closed Strings In Ramond-Ramond Backgrounds, Vatche Sahakian

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We write the IIB Green-Schwarz action in certain general classes of curved backgrounds threaded with Ramond-Ramond fluxes. The fixing of the kappa symmetry in the light-cone gauge and the use of supergravity Bianchi identities simplify the task. We find an expression that truncates to quartic order in the spacetime spinors and relays interesting information about the vacuum structure of the worldsheet theory. The results are particularly useful in exploring integrable string dynamics in the context of the holographic duality.


Holography With Ramond-Ramond Fluxes, Vatche Sahakian Jan 2003

Holography With Ramond-Ramond Fluxes, Vatche Sahakian

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Starting from the non-linear sigma model of the IIB string in the light-cone gauge, we analyze the role of RR fluxes in Holography. We find that the worldsheet theory of states with only left or right moving modes does not see the presence of RR fields threading a geometry. We use this significant simplification to compute part of the strong coupling spectrum of the two dimensional NCOS theory. We also reproduce the action of a closed string in a PP-wave background using this general formalism; and we argue for various strategies to find new systems where the closed string theory ...


The Large M Limit Of Non-Commutative Open Strings At Strong Coupling, Vatche Sahakian Jan 2002

The Large M Limit Of Non-Commutative Open Strings At Strong Coupling, Vatche Sahakian

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Two-dimensional Non-Commutative Open String (NCOS) theory, well-defined perturbatively, may also be studied at strong coupling and for large D-string charge by making use of the Holographic duality. We analyze the zero mode dynamics of a closed string in the appropriate background geometry and map the results onto a sector of strongly coupled NCOS dynamics. We find an elaborate classical picture that shares qualitative similarities with the SL(2,R) WZW model. In the quantum problem, we compute propagators and part of the energy spectrum of the theory; the latter involves interesting variations in the density of states as a function ...


Transcribing Spacetime Data Into Matrices, Vatche Sahakian Jun 2001

Transcribing Spacetime Data Into Matrices, Vatche Sahakian

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In certain supergravity backgrounds, D0 branes may polarize into higher dimensional Dp branes. We study this phenomenon in some generality from the perspective of a local inertial observer and explore polarization effects resulting from tidal-like forces. We find D2 brane droplets made of D0 branes at an extremum of the Born-Infeld action even in scenarios where the RR fields may be zero. These solutions lead us to a local formulation of the UV-IR correspondence. A holographic Planck scale bound on the number of D0 branes plays an important role in the analysis. We focus on the impact of higher order ...


On D0 Brane Polarization By Tidal Forces, Vatche Sahakian May 2001

On D0 Brane Polarization By Tidal Forces, Vatche Sahakian

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Gravitational tidal forces may induce polarization of D0-branes, in analogy to the same effects arising in the context of constant background gauge fields. Such phenomena can teach us about the correspondence between smooth curved spacetime and its underlying non-commutative structure. However, unlike polarization by gauge fields, the gravitational counterpart involves concerns regarding the classical stability of the corresponding polarized states. In this work, we study this issue with respect to the solutions presented in hepth0010237 and find that they are classically unstable. The instability however appears with intricate features with all but a few decay channels being lifted. Through a ...


Holography, A Covariant C Function, And The Geometry Of The Renormalization Group, Vatche Sahakian Nov 2000

Holography, A Covariant C Function, And The Geometry Of The Renormalization Group, Vatche Sahakian

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We propose a covariant geometrical expression for the c function for theories which admit dual gravitational descriptions. We state a c theorem with respect to this quantity and prove it. We apply the expression to a class of geometries, from domain walls in gauged supergravities, to extremal and near extremal Dp-branes, and the AdS Schwarzschild black hole. In all cases, we find agreement with expectations.


The Phases Of 2d Ncos, Vatche Sahakian Oct 2000

The Phases Of 2d Ncos, Vatche Sahakian

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We study the phases of the (1+1)-dimensional Non-Commutative Open String theory on a circle. We find that the length scale of non-commutativity increases at strong coupling, the coupling in turn being dressed by a power of D-string charge. The system is stringy at around this length scale, with dynamics involving an interplay between the open and wrapped closed strings sectors. Above this energy scale and at strong coupling, and below it at weak coupling, the system acquires a less stringy character. The near horizon geometry of the configuration exhibits several intriguing features, such as a flip in the ...


Comments On D Branes And The Renormalization Group, Vatche Sahakian Jun 2000

Comments On D Branes And The Renormalization Group, Vatche Sahakian

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We review the de Boer-Verlinde-Verlinde formalism for the renormalization group in the context of Dp-brane vacua for p < 5. We comment on various aspects of the dictionary between bulk and boundary and relate the discussion to the Randall-Sundrum scenario. We find that the gravitational coupling for the Randall-Sundrum gravity on the Dp-brane worldvolume is dressed by the c-function of the Yang-Mills theory. We compute the beta function and find the expected uneventful flow prescribed by the classical dimension of the Yang-Mills operator.


Black Holes And Five-Brane Thermodynamics, Emil Martinec, Vatche Sahakian Aug 1999

Black Holes And Five-Brane Thermodynamics, Emil Martinec, Vatche Sahakian

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The phase diagram for Dp-branes in M theory compactified on T4,T4/Z2,T5, and T6 is constructed. As for the lower-dimensional tori considered in our previous work [E. Martinec and V. Sahakian, Phys. Rev. D 59, 124005 (1999)], the black brane phase at high entropy connects onto matrix theory at low entropy; we thus recover all known instances of matrix theory as consequences of the Maldacena conjecture. The difficulties that arise for T6 are reviewed. We also analyze the D1-D5 system on T5; we discuss its relation to matrix models of M5-branes ...


Black Holes And The Sym Diagram. Ii, Emil Martinec, Vatche Sahakian May 1999

Black Holes And The Sym Diagram. Ii, Emil Martinec, Vatche Sahakian

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The complete phase diagram of objects in M theory compactified on tori Tp,p=1,2,3, is elaborated. Phase transitions occur when the object localizes on cycle(s) (the Gregory-Laflamme transition), or when the area of the localized part of the horizon becomes one in string units (the Horowitz-Polchinski correspondence point). The low-energy, near-horizon geometry that governs a given phase can match onto a variety of asymptotic regimes. The analysis makes it clear that the matrix conjecture is a special case of the Maldacena conjecture.


Black Holes And The Sym Phase Diagram, Miao Li, Emil Martinec, Vatche Sahakian Jan 1999

Black Holes And The Sym Phase Diagram, Miao Li, Emil Martinec, Vatche Sahakian

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Making combined use of the matrix and Maldacena conjectures, the relation between various thermodynamic transitions in super Yang-Mills (SYM) theory and supergravity is clarified. The thermodynamic phase diagram of an object in DLCQ M theory in four and five non-compact space dimensions is constructed; matrix strings, matrix black holes, and black p-branes are among the various phases. Critical manifolds are characterized by the principles of correspondence and longitudinal localization, and a triple point is identified. The microscopic dynamics of the matrix string near two of the transitions is studied; we identify a signature of black hole formation from SYM physics.