arXiv subjects

Marcelo Botta Cantcheff

Publications and source records attributed to Marcelo Botta Cantcheff.

15 recordsLinked to original sources

arXiv2025

Signature change as phase transition in holography

In holographic quantum gravity, Euclidean pieces of the spacetime appear in the large N limit as representing semi-classical states of the theory. In this essay, we argue that the duals of entangled states are spacetime geometries that contain Euclidean regions in order to preserve classical connectivity. Thereby, the proposal is to extend the ER-EPR conjecture to regimes whether wormholes (Einstein-Rosen bridges) become unstable but the entangled structure of the dual state persists.

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arXiv2023

Spacetime topology from holographic entanglement

An asymptotically AdS geometry connecting two or more boundaries is given by a entangled state, that can be expanded in the product basis of the Hilbert spaces of each CFT living on the boundaries. We derive a prescription to compute this expansion for states describing spacetimes with general spatial topology in arbitrary dimension. To large N, the expansion coincides with the Schmidt decomposition and the coefficients are given by $n$-point correlation functions on a particular Euclidean geometry. We show that this applies to all spacetime that admits a Hartle-Hawking type of wave functional, which via a standard hypothesis on the spatial topology, can be (one to one) mapped to CFT states defined on the asymptotic boundary. It is also observed that these states are endowed with quantum coherence properties. Applying this as holographic engineering, one can to construct an emergent space geometry with certain predetermined topology by preparing an entangled state of the dual quantum system. As an example, we apply the method to calculate the expansion and characterize a spacetime whose initial spatial topology is a (genus one) handlebody.

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arXiv2014

Area Operators in Holographic Quantum Gravity

We argue that the holographic formula relating entanglement entropy and the area of a minimal surface is the key to define the area of surfaces in the (emergent) spacetime from the dual theory on the boundary. So we promote the entropy/area relation to operators to define the "area" observable in a holographic formulation of quantum gravity, then we find a suitable geometric representation for the states, and show that the Ryu-Takayanagi proposal is recovered in the approximation of semi-classical gravity. Finally, we discuss this picture in the example of a AdS-Black hole.

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arXiv2012

Quantum states of the spacetime, and formation of black holes in AdS

We argue that a non-perturbative description of quantum gravity should involve two (non-interacting) copies of a dual field theory on the boundary, and describe the states of the spacetimes accordingly. So, for instance, a complete description of the asymptotically Anti-de-Sitter spacetimes is given by two copies of the conformal field theory associated to the global AdS spacetime. We also argue that, in this context, gravitational collapse and formation of a black hole may be described by unitary evolution of the dual non-perturbative degrees of freedom.

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arXiv2011

Emergent spacetime, and a model for unitary gravitational collapse in AdS

We propose a CFT unitary description of the gravitational collapse. The starting point is the model of a black hole in AdS proposed by Maldacena in arXiv: 0106112 [hep-th]. We show that by proposing a two-copies version of the AdS/CFT conjecture, the process of formation of black holes so as other spacetimes with horizons may be described as an unitary process in the dual field theory. In doing this, we construct a well defined framework to describe general spacetimes as entangled states, in terms of the spectrum of states on the exact Anti-de-Sitter background. As application, we show how the description of the Hawking-Page transition results simplified in this formalism and some novel aspects may be observed. Finally, a simplified analysis based on weakly coupled bulk fields is discussed.

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arXiv2011

Spacetime Geometry as Statistic Ensemble of Strings

Jacobson theorem (Ref. \cite{jacobson}) shows that Einstein gravity may be understood as a thermodynamical equation of state; a microscopic realization of this result is however lacking. In this paper, we propose that this may be achieved by assuming the spacetime geometry as a macroscopic system, whose thermodynamical behavior is described by a statistical ensemble, whose microscopic components are low-dimensional geometries. We show that this picture is consistent with string theory by proposing a particular model for the microscopic geometry, where the spacetime metric plays the role of an ordinary thermodynamical potential in a special ensemble. In this scenario, Einstein equation is indeed recovered as an equation of state, and the black hole thermodynamics is reproduced in a thermodynamic limit (large length scales). The model presented here is background-independent and, in particular, it provides an alternative formulation of string theory.

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arXiv2009

String Entanglement and D-branes as Pure States

We study the entanglement of closed strings degrees of freedom in order to investigate the microscopic structure and statistics of objects as D-branes. By considering the macroscopic pure state (MPS) limit, whenever the entanglement entropy goes to zero (in such a way that the macroscopic properties of the state are preserved), we show that boundary states may be recovered in this limit and, furthermore, the description through closed string (perturbative) degrees of freedom collapses. We also show how the thermal properties of branes and closed strings could be described by this model, and it requires that dissipative effects be taken into account. Extensions of the MPS analysis to more general systems at finite temperature are finally emphasized.

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arXiv2008

Einstein-Cartan formulation of Chern-Simons Lorentz-violating Gravity

We consider a modification of the standard Einstein theory in four dimensions, alternative to R. Jackiw and S.-Y. Pi, Phys. Rev. D 68, 104012 (2003), since it is based on the first-order (Einstein-Cartan) approach to General Relativity, whose gauge structure is manifest. This is done by introducing an additional topological term in the action which becomes a Lorentz-violating term by virtue of the dependence of the coupling on the space-time point. We obtain a condition on the solutions of the Einstein equations, such that they persist in the deformed theory, and show that the solutions remarkably correspond to the classical solutions of a collection of independent 2+1-d (topological) Chern-Simons gravities. Finally, we study the relation with the standard second-order approach and argue that they both coincide to leading order in the modulus of the Lorentz-violating vector field.

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arXiv2008

D-branes as coherent states in the open string channel

We show that bosonic D-brane states may be represented as coherent states in an open string representation. By using the Thermo-Field Dynamics (TFD) formalism, we may construct a condensed state of open string modes which encodes the information on the D-brane configuration. We also introduce a construction alternative to TFD, which does not requires to assume thermal equilibrium. It is shown that the dynamics of the system combined with geometric properties of the duplication rules of TFD is sufficient to obtain the thermal states and their analytic continuations in a geometric fashion. We use this approach to show that bosonic D-brane state in the open string sector may also be built as boundary states in a special sense. Some implications of this study on the interpretation of the open/closed duality and on the kinemathic/algebraic structure of an open string field theory are also commented.

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arXiv2006

Lorentz Symmetry Breaking and Planar Effects from Non-Linear Electrodynamics

We propose a modification of standard linear electrodynamics in four dimensions, where effective non-trivial interactions of the electromagnetic field with itself and with matter fields induce Lorentz violating Chern-Simons terms. This yields two consequences: it provides a more realistic and general scenario for the breakdown of Lorentz symmetry in electromagnetism and it may explain the effective behavior of the electromagnetic field in certain planar phenomena (for instance, Hall effect). A number of proposals for non-linear electrodynamics is discussed along the paper. Important physical implications of the breaking of Lorentz symmetry, such as optical birefringence and the possibility of having conductance in the vacuum are commented on.

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arXiv2005

Non-Boltzmann Statistics as an Alternative to Holography

An intriguing question related to black hole thermodynamics is that the entropy of a region shall scale as the area rather than the volume. In this essay we propose that the microscopical degrees of freedom contained in a given region of space, are statistically related in such a way that obey a non-standard statistics, in which case an holographic hypothesis would be not needed. This could provide us with some insight about the nature of degrees of freedom of the geometry and/or the way in which gravitation plays a role in the statistic correlation between the degrees of freedom of a system.

gr-qc↗

arXiv2004

Doublet Groups, Extended Lie Algebras, and Well Defined Gauge Theories for the Two Form Field

We propose a symmetry law for a doublet of different form fields, which resembles gauge transformations for matter fields. This may be done for general Lie groups, resulting in an extension of Lie algebras and group manifolds. It is also shown that non-associative algebras naturally appear in this formalism, which are briefly discussed. Afterwards, a general connection which includes a two-form field is settled-down, solving the problem of setting a gauge theory for the Kalb-Ramond field for generical groups. Topological Chern-Simons theories can also be defined in four dimensions, and this approach clarifies their relation to the so-called $B \wedge F$-theories. We also revise some standard aspects of Kalb-Ramond theories in view of these new perspectives. Since this gauge connection is built upon a pair of fields consisting of a one-form and a two-form, one may define Yang-Mills theories as usually and, remarkably, also {\it minimal coupling} with bosonic matter, where the Kalb-Ramond field appears naturally as mediator; so, a new associated conserved charge can be defined. For the Abelian case, we explicitly construct the minimal interaction between $B$-field and matter following a "gauge principle" and find a novel conserved tensor current. This is our most significative result from the physical viewpoint. This framework is also generalized in such a way that any $p$-rank tensor may be formulated as a gauge field.

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arXiv2004

On the Microscopical Structure of the Classical Spacetime

Our purpose here is to introduce the idea of viewing the spacetime as a macroscopic complex system which, consequently, cannot be directly quantized. It should be thought of as a collection of more fundamental "microscopical" entities (atoms of geometry), much like a solid system, in which an atomic (classical) structure must be first recognized in order to ensure a correct and meaningful quantization procedure. In other words, we claim that the classical limit from a quantum theory of gravity could not give a four dimensional Einstein spacetime directly, but requiring {\it a further} macroscopical limit. This is analogous to a material medium, whose complete description does not come from any quantized field. We also discuss a possible realization of this hypothesis for black hole spacetimes.

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arXiv2003

2-Form Gauge Field Theories and "No Go" for Yang-Mills Relativistic Actions

The transformation properties of a Kalb-Ramond field are those of a gauge potential. However, it is not clear what is the group structure to which these transformations are associated. In this paper, we complete a program started in previous articles in order to clarify this question. Using the spectral theorem, we improve and generalize previous approaches and find the possible group structures underneath the 2-form gauge potential as extensions of Lie groups, when its representations are assumed to act into any tensor (or spinor) space with inner product. We also obtain a fundamental representation where a two-form field turns out to be a connection on a flat Euclidean basis manifold, with a corresponding canonical curvature. However, we show that these objects are not associated to space-time tensors and, in particular, that a standard Yang-Mills action is not relativistically invariant, except (as expected) in the Abelian case. This is our main result, from the physical point of view.

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arXiv1998

The "phenomenological" spacetime and quantization

In order to obtain a well defined quantum gravity we define the spacetime in relation to the "phenomenology" of the physical interactions; however we shall to speculate with this "in General". Besides, we comment the reasons that give to the gravitational field a privilegied situation over the others.

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