Scalar Collapse Research Articles

Scale(s) of Sexuate Difference

Technofeminism has long known that it must be a multi-scalar feminism, that is, able to think, encounter, and negotiate these increasing scales of complexity that comprise our world, from the pharmacological to the planetary-computational. We read technofeminism as constitutively defined by its commitment to both realism and anti-essentialism, and contemporary technofeminisms to be epitomised by, on the one hand, the flat vitalist ontology of new materialism, and on the other, the trans-scalar rationalism of Xenofeminism. By examining these contemporary technofeminisms through contemporary theorisations of the concept of scale, we show that they have a problem with what the latter identify as ‘scalar collapse’; these technofeminisms conceptualise the multi-scalarity of reality, in the last instance, via a collapse into either the ‘master scale’ of new materialist ‘matter’, or via the ‘trans-scalar zoom’ of Xenofeminist rationalism. As such, they recoil from the reality of scalar differences, undermining their commitment to realism (and therefore technics), as well as reducing scalar difference to one unitary, ‘metaphysical’ ground, placing them back within an essentialist collapse. Through examining contemporary theorisations of scale, we claim that in order to avoid such scalar collapse, any truly multi-scalar theory must think difference as both ontogenetic, in the Simondonian sense, and irreducibly at-least-two, in the sense of Irigaray’s concept of sexuate difference. Against any concerns that Irigaray’s notion of sexuate difference may be essentialist or determinist, we show that the ontogenetic character of this difference means it is irreducible and yet also open-ended, that is, open to multiply complex, topologically scalar transformations throughout subsequent individuations. It is this thinking of difference as this ontogenetic ‘at least two’ that can enable contemporary technofeminisms to be truly multi-scalar feminisms.

Unruly Microcosms in Contemporary Eco-Fiction

Abstract: This article theorizes the disruptive epistemic work performed by microcosms in recent eco-fiction. Contemporary fiction often explores large-scale ecological disruption through smaller organisms and environments, enabling readers to perceive the Earth through analogy, allegory and metaphor. Within and against this scale-free reading, I argue that the microcosm has become a fracturing trope that troubles relations between scales. Drawing on fiction by T. C. Boyle, A. S. Byatt, Amitav Ghosh, Ali Smith, and Karen Tei Yamashita, I read the microcosm as a critical tool of Anthropocene awareness, because it foregrounds and questions scalar collapse –the epistemic projection of one scale onto another.

Complexity of scalar collapse in anti-de Sitter spacetime

We calculate the volume and action forms of holographic complexity for the gravitational collapse of scalar field matter in asymptotically anti-de Sitter spacetime, using numerical methods to reproduce the geometry responding to the oscillating field over multiple crossing times. Like the scalar field pulse, the volume complexity oscillates quasiperiodically before horizon formation. It also shows a scaling symmetry with the amplitude of the scalar field. The action complexity is also quasiperiodic with spikes of increasing amplitude.

Cosmic censorship of trans-Planckian field ranges in gravitational collapse

A classical solution where the (scalar) field value moves by an O(1) range in Planck units is believed to signal the breakdown of Effective Field Theory (EFT). One heuristic argument for this is that such a field will have enough energy to be inside its own Schwarzschild radius, and will result in collapse. In this paper, we consider an inverse problem: what kind of field ranges arise during the gravitational collapse of a classical field? Despite the fact that collapse has been studied for almost a hundred years, most of the discussion is phrased in terms of fluid stress tensors, and not fields. An exception is the scalar collapse made famous by Choptuik. We re-consider Choptuik-like systems, but with the emphasis now on the evolution of the scalar. We give strong evidence that generic spherically symmetric collapse of a massless scalar field leads to super-Planckian field movement. But we also note that in every such supercritical collapse scenario, the large field range is hidden behind an apparent horizon. We also discuss how the familiar perfect fluid models for collapse like Oppenheimer-Snyder and Vaidya should be viewed in light of our results.

Scalar collapse in AdS with an OpenCL open source code

We study the spherically symmetric collapse of a scalar field in anti-de Sitter spacetime using a newly constructed, open-source code which parallelizes over heterogeneous architectures using the open standard OpenCL. An open question for this scenario concerns how to tell, a priori, whether some form of initial data will be stable or will instead develop under the turbulent instability into a black hole in the limit of vanishing amplitude. Previous work suggested the existence of islands of stability around quasi-periodic solutions, and we use this new code to examine the stability properties of approximately quasi-periodic solutions which balance energy transfer to higher modes with energy transfer to lower modes. The evolutions provide some evidence, though not conclusively, for stability of initial data sufficiently close to quasiperiodic solutions.

Spherical vacuum and scalar collapse for the StarobinskyR2model

Spherical vacuum and scalar collapse for the Starobinsky R^2 model is simulated. Obtained by considering the quantum-gravitational effects, this model would admit some cases of singularity-free cosmological spacetimes. It is found, however, that in vacuum and scalar collapse, when f' or the physical scalar field is strong enough, a black hole including a central singularity can be formed. In addition, near the central singularity, gravity dominates the repulsion from the potential, so that in some circumstances the Ricci scalar is pushed to infinity by gravity. Therefore, the semiclassical effects as included here do not avoid the singularity problem in general relativity. A strong physical scalar field can prevent the Ricci scalar from growing to infinity. Vacuum collapse for the RlnR model is explored, and it is observed that for this model the Ricci scalar can also go to infinity as the central singularity is approached. Therefore, this feature seems universal in vacuum and scalar collapse in f(R) gravity.

Charged scalar gravitational collapse in de Sitter spacetime

We study the charged scalar collapse in de Sitter spacetimes. With the electric charge, there is one more competitor to join the competition of dynamics in the gravitational collapse. We find that two factors can influence the electric charge. If we just adjust the charge conjugation, the electric charge effect is always perturbative at the black hole threshold. The electric charge can also be influenced by the initial conditions of perturbations. These initial parameters can be tuned to control the competition in dynamics and present us new and rich physics in the process of gravitational collapse. We give physical explanations on these phenomena found in dynamics. Furthermore we show that the properties of the gravitational collapse are universal and do not depend on spacetime dimensions.

Mass inflation and curvature divergence near the central singularity in spherical collapse

We study spherical scalar collapse toward a black hole formation and examine the asymptotic dynamics near the central singularity of the formed black hole. It is found that, in the vicinity of the singularity, due to the strong backreaction of a scalar field on the geometry, the mass function inflates and the Kretschmann scalar grows faster than in the Schwarzschild geometry. In collapse, the Misner-Sharp mass is a locally conserved quantity, not providing information on the black hole mass that is measured at asymptotically flat regions.

Interior dynamics of neutral and charged black holes

In this paper, we explore the interior dynamics of neutral and charged black holes. Scalar collapses in flat, Schwarzschild, and Reissner-Nordstr\"om background geometries are simulated. We examine the dynamics in the vicinities of the central singularity of a Schwarzschild black hole and of the inner horizon of a Reissner-Nordstr\"om black hole. In simulating scalar collapses in Schwarzschild and Reissner-Nordstr\"om geometries, Kruskal and Kruskal-like coordinates are used, respectively, with the presence of a scalar field being taken into account. It is found that, besides near the inner horizons of Reissner-Nordstr\"om and Kerr black holes, mass inflation also takes place near the central singularity in neutral scalar collapse. Approximate analytic expressions for different types of mass inflation are partially obtained via a close interplay between numerical and analytical approaches and an examination of the connections between Schwarzschild black holes, Reissner-Nordstr\"om black holes, neutral collapse, and charge scattering. We argue that the mass inflations near the central singularity and the inner horizon are related to the localness of the dynamics in strong gravity regions. This is in accord with the Belinskii, Khalatnikov, and Lifshitz conjecture.

Spherical collapse inf(R)gravity and the Belinskii-Khalatnikov-Lifshitz conjecture

Spherical scalar collapse in $f(R)$ gravity is studied numerically in double-null coordinates in Einstein frame. Dynamics in the vicinity of the singularity of the formed black hole is examined via mesh refinement and asymptotic analysis. Before the collapse, the scalar degree of freedom ${f}^{\ensuremath{'}}$ is coupled to a physical scalar field, and general relativity is restored. During the collapse, the major energy of the physical scalar field moves to the center. As a result, ${f}^{\ensuremath{'}}$ loses the coupling and becomes light, and gravity transits from general relativity to $f(R)$ gravity. Due to strong gravity from the singularity and the low mass of ${f}^{\ensuremath{'}}$, ${f}^{\ensuremath{'}}$ will cross the minimum of the potential and approach zero. Therefore, the dynamical solution is significantly different from the static solution of the black hole in $f(R)$ gravity---it is not the de Sitter-Schwarzschild solution as one might have expected. ${f}^{\ensuremath{'}}$ tries to suppress the evolution of the physical scalar field, which is a dark energy effect. As the singularity is approached, metric terms are dominant over other terms. The Kasner solution for spherical scalar collapse in $f(R)$ theory is obtained and confirmed by numerical results. These results support the Belinskii-Khalatnikov-Lifshitz conjecture well.

Scalar collapse in AdS spacetimes

Recently, studies of the gravitational collapse of a scalar field within spherically symmetric anti--de Sitter (AdS) spacetimes presented by Bizon and Rostroworoski [Phys. Rev. Lett. 107, 031102 (2011)], Jalmuzna et al. [Phys. Rev. D 84, 085021 (2011).] showed an instability of pure AdS to black hole formation. In particular, the work showed that arbitrarily small initial configurations of a scalar field evolved through some number of reflections off the AdS boundary until a black hole forms. We consider this same system, extended to include a complex scalar field, and reproduce this phenomena. We present tests of our numerical code that demonstrate convergence and consistency. We study the properties of the evolution as the scalar pulse becomes more compact by examining the asymptotic behavior of the scalar field, an observable in the corresponding boundary conformal field theory. We demonstrate that such black hole formation occurs even when one places a reflecting boundary at finite radius, indicating that the sharpening is a property of gravity in a bounded domain and not of AdS itself. We examine how the initial energy is transferred to higher frequencies---which leads to black hole formation---and uncover interesting features of this transfer.

Kink stability of self-similar solutions of scalar field in 2 + 1 gravity

The kink stability of self-similar solutions of a massless scalar field with circular symmetry in 2 + 1 gravity is studied, and found that such solutions are unstable against the kink perturbations along the sonic line (self-similar horizon). However, when perturbations outside the sonic line are considered, and taking the ones along the sonic line as their boundary conditions, we find that non-trivial perturbations do not exist. In other words, the consideration of perturbations in the whole spacetime limits the unstable mode of the perturbations found along the sonic line, and the kink instability rises because of the incomplete treatment of the problem. As a result, the critical solution for the scalar collapse remains critical even after the kink perturbations are taken into account.

Critical phenomena and relativistic gravitational collapse

Recent calculations have shown the existence of critical phenomena in general relativity associated with the collapse of wavepackets of massless fields that are near, in parameter space, the onset of black hole formation (the critical point). Two physically distinct systems have been explored: collapse of spherically-symmetric massless scalar field and collapse of vacuum, axisymmetric gravitational waves. Nonlinear effects dominate near the critical point. Black-hole mass serves as an order parameter and has a power-law dependence on critical separation in the supercritical region of parameter space. Remarkably, the values of the critical exponent of the power law are nearly identical in the two systems. The nonlinearity induces the fields to oscillate. Each successive oscillation is an echo, obeying a spatial and temporal scaling relation.