Are There Topological Black Hole Solitons in String Theory?

We point out that the celebrated Hawking effect of quantum instability of black holes seems to be related to a nonperturbative effect in string theory. Studying quantum dynamics of strings in the gravitational background of black holes we find classical instability due to emission of massless string excitations. The topology of a black hole seems to play a fundamental role in developing the string theory classical instability due to the effect of sigma model instantons. We argue that string theory allows for a qualitative description of black holes with very small masses and it predicts topological solitons with quantized spectrum of masses. These solitons would not decay into string massless excitations but could be pair created and may annihilate also. Semiclassical mass quantization of topological solitons in string theory is based on the argument showing existence of nontrivial zeros of beta function of the renormalization group.Comment: 12 pages, TeX, requires phyzzx.tex, published in Gen. Rel. Grav. 19 (1987) 1173; comment added on December 18, 199

String Physics and Black Holes

In these lectures we review the quantum physics of large Schwarzschild black holes. Hawking's information paradox, the theory of the stretched horizon and the principle of black hole complementarity are covered. We then discuss how the ideas of black hole complementarity may be realized in string theory. Finally, arguments are given that the world may be a hologram. Lectures delivered at ICTP Spring School on String Theory, Gauge Theory, and Quantum Gravity, 1995.Comment: 20 pages, Latex (needs espcrc2.sty), 6 figure

Committed to the Fragment: Feminist Literature and the Promise of Wellness

“I have never been able to blind myself” to the cruelty of a world that “destroys its own young in passing…out of not noticing or caring about the destruction,” Audre Lorde tells us in her 1980 “mythobiography” Zami: A New Spelling of My Name. This quality, Lorde says, “according to one popular definition of mental health, makes me mentally unhealthy.” In rejecting psychological self-possession as a sign of wellness, this passage also rejects it as one of sovereignty’s conditions. At the time of Lorde’s writing, this version of sovereignty already dominated the landscape of therapeutic culture in the United States, and would become only more staggeringly pervasive and profitable in the years to come. In our therapeutic age, to establish oneself as one of neoliberalism’s winners requires performing a healthist form of psychic well-being -- one that overlaps with Enlightenment ideals of autonomy and rationality. This dissertation explores how literary genres and forms reject psychic well-being as a privilege of bourgeois liberalism and a panacea for heteronormativity’s discontents. These texts are what I read as “feminist literature.” They turn to emergent genres and forms to refigure wellness as a generative relation to difference – a relation that, in Lorde’s Black feminist framework, is always bound up with the pain of others. Specifically, I read Lorde’s genre-bending memoir The Cancer Journals; the post-2016 genre of self-care comedy; and autotheory about the Diagnostic and Statistical Manual of Mental Disorders (DSM) as examining how sexist, racist, and ableist ideals of wellness have placed fraught and contradictory demands on the feminist subject. I argue that these texts represent the writing process itself as crucial for addressing this question: a site for revising the literary conventions that evince a liberal subject’s mind at work, as well as for interrogating how medicalized norms structure writing cultures, academic and otherwise. Writing appears across a range of genres – memoir; fiction; cultural criticism; and autotheory – as a practice that identifies illness, wellness, and aesthetics as pressingly concerned with gender and power

D-brane Approach to Black Hole Quantum Mechanics

Strominger and Vafa have used D-brane technology to identify and precisely count the degenerate quantum states responsible for the entropy of certain extremal, BPS-saturated black holes. Here we give a Type-II D-brane description of a class of extremal {\it and} non-extremal five-dimensional Reissner-Nordstr\"om solutions and identify a corresponding set of degenerate D-brane configurations. We use this information to do a string theory calculation of the entropy, radiation rate and ``Hawking'' temperature. The results agree perfectly with standard Hawking results for the corresponding nearly extremal Reissner-Nordstr\"om black holes. Although these calculations suffer from open-string strong coupling problems, we give some reasons to believe that they are nonetheless qualitatively reliable. In this optimistic scenario there would be no ``information loss'' in black hole quantum evolution.Comment: 18 pages, uses harvmac and psfig. The new version of the paper corrects various errors, omissions and obscurities of the original submission. The major error was an underestimate of the severity of the strong coupling problem in the D-brane description of black holes with a macroscopic event horizon. The new version has a more sober, but still optimistic assessment of what aspects of black hole quantum mechanics are be brought under control by D-branes. We thank several correspondents for helpful criticism and advic

Degrees of freedom in two dimensional string theory

We discuss two issues regarding the question of degrees of freedom in two dimensional string theory. The first issue relates to the classical limit of quantum string theory. In the classical theory one requires an infinite number of fields in addition to the collective field to describe ``folds'' on the fermi surface. We argue that in the quantum theory these are not additional degrees of freedom. Rather they represent quantum dispersions of the collective field which are {\em not} suppressed when $\hbar \rightarrow 0$ whenever a fold is present, thus leading to a nontrivial classical limit. The second issue relates to the ultraviolet properties of the geometric entropy. We argue that the geometric entropy is finite in the ultraviolet due to {\em nonperturbative} effects. This indicates that the true degrees of freedom of the two dimensional string at high energies is much smaller than what one naively expects. (Based on talks at Spring Workshop on String theory and Quantum Gravity, ICTP, Trieste, March 1995 and VIIth Regional Conference on Mathematical Physics, Bandar-Anzali, October 1995.)Comment: 18 pages, LaTe

Solitons, Black Holes and Duality in String Theory

These lectures are intended as an introduction to some of the basic aspects of string solitons, duality and black holes. We begin with a discussion of the role of classical solutions in duality, then focus on string/string duality and fundamental membranes. Finally, we examine the feature of compositeness of string solitons, and its implications for bound states and black hole thermodynamics. As these lectures are aimed primarily at those less familiar with this field, technical details are minimized.Comment: 12 pages, LaTex (minor error corrected

Upper bound for entropy in asymptotically de Sitter space-time

We investigate nature of asymptotically de Sitter space-times containing a black hole. We show that if the matter fields satisfy the dominant energy condition and the cosmic censorship holds in the considering space-time, the area of the cosmological event horizon for an observer approaching a future timelike infinity does not decrease, i.e. the second law is satisfied. We also show under the same conditions that the total area of the black hole and the cosmological event horizon, a quarter of which is the total Bekenstein-Hawking entropy, is less than $12\pi/\Lambda$, where $\Lambda$ is a cosmological constant. Physical implications are also discussed.Comment: 9 pages, REVTeX,2 figures; to be published in Phys.Rev.

Instability of Extremal Relativistic Charged Spheres

With the question, ``Can relativistic charged spheres form extremal black holes?" in mind, we investigate the properties of such spheres from a classical point of view. The investigation is carried out numerically by integrating the Oppenheimer-Volkov equation for relativistic charged fluid spheres and finding interior Reissner-Nordstr\"om solutions for these objects. We consider both constant density and adiabatic equations of state, as well as several possible charge distributions, and examine stability by both a normal mode and an energy analysis. In all cases, the stability limit for these spheres lies between the extremal ($Q = M$) limit and the black hole limit ($R = R_+$). That is, we find that charged spheres undergo gravitational collapse before they reach $Q = M$, suggesting that extremal Reissner-Nordtr\"om black holes produced by collapse are ruled out. A general proof of this statement would support a strong form of the cosmic censorship hypothesis, excluding not only stable naked singularities, but stable extremal black holes. The numerical results also indicate that although the interior mass-energy $m(R)$ obeys the usual $m/R < 4/9$ stability limit for the Schwarzschild interior solution, the gravitational mass $M$ does not. Indeed, the stability limit approaches $R_+$ as $Q \to M$. In the Appendix we also argue that Hawking radiation will not lead to an extremal Reissner-Nordstr\"om black hole. All our results are consistent with the third law of black hole dynamics, as currently understood

Generalized entropy and Noether charge

We find an expression for the generalized gravitational entropy of Hawking in terms of Noether charge. As an example, the entropy of the Taub-Bolt spacetime is calculated.Comment: 6 pages, revtex, reference correcte