Probe String Research Articles

Complexity growth of rotating black holes with a probe string

We study the effect of a probe string to black hole complexity according to the CA (Complexity equals Action) conjecture. Our system contains a particle moving on the boundary of black hole spacetime. In the dual description this corresponds to the insertion of a fundamental string on the bulk spacetime. The total action consists of the Einstein-Hilbert term and the Nambu-Goto term. The effect of this string is expressed by the Nambu-Goto term. Focusing on the Nambu-Goto term, we analyse the time development of this system. Our results show some interesting properties of complexity. This gives a useful hint for defining complexity in quantum field theories.

Remember to blink: Reduced attentional blink following instructions to forget.

This study used rapid serial visual presentation (RSVP) to determine whether, in an item-method directed forgetting task, study word processing ends earlier for forget words than for remember words. The critical manipulation required participants to monitor an RSVP stream of black nonsense strings in which a single blue word was embedded. The next item to follow the word was a string of red fs that instructed the participant to forget the word or green rs that instructed the participant to remember the word. After the memory instruction, a probe string of black xs or os appeared at postinstruction positions 1-8. Accuracy in reporting the identity of the probe string revealed an attenuated attentional blink following instructions to forget. A yes-no recognition task that followed the study trials confirmed a directed forgetting effect, with better recognition of remember words than forget words. Considered in the context of control conditions that required participants to commit either all or none of the study words to memory, the pattern of probe identification accuracy following the directed forgetting task argues that an intention to forget releases limited-capacity attentional resources sooner than an instruction to remember-despite participants needing to maintain an ongoing rehearsal set in both cases.

(p,q)-strings probing five-brane webs

In recent work, globally well-defined Type IIB supergravity solutions with geometry AdS6 × S2 warped over a Riemann surface Σ were constructed and conjectured to describe the near-horizon geometry of (p, q) five-brane webs in the conformal limit. In the present paper, we offer more evidence for this interpretation of the supergravity solutions in terms of five-brane webs. In particular, we explore the behavior of probe (p, q)-strings in certain families of these AdS6 × S2 × Σ backgrounds and compare this behavior to that predicted by microscopic, brane web considerations. In the microscopic picture, we argue that the embedding of a probe string may give rise to the formation of string junctions involving open strings anchored on the branes of the web. We then identify a quantity on the supergravity side that is conjectured to be equivalent to the total junction tension in a class of backgrounds corresponding to brane webs with four semi-infinite external five-branes. In the process, we will show that for general brane web backgrounds, the minimal energy probe string embeddings do not coincide with the embeddings preserving half of the background supersymmetries.

SL(2,\xa0Z) invariant rotating (m,\xa0n) strings in AdS_3times S^3 with mixed flux

We study rigidly rotating and pulsating (m, n) strings in AdS_3 times S^3 with mixed three form flux. The AdS_3 times S^3 background with mixed three form flux is obtained in the near horizon limit of SL(2, Z)-transformed solution, corresponding to the bound state of NS5-branes and fundamental strings. We study the probe (m, n)-string in this background by solving the manifest SL(2, Z)-covariant form of the action. We find the dyonic giant magnon and single spike solutions corresponding to the equations of motion of a probe string in this background and find various relationships among the conserved charges. We further study a class of pulsating (m, n) string in AdS_3 with mixed three form flux.

Aharonov–Bohm protection of black hole's baryon/skyrmion hair

The baryon/skyrmion correspondence implies that the baryon number is encoded into a topological surface integral. Under certain conditions that we clarify, this surface integral can be measured by an asymptotic observer in form of an Aharonov–Bohm phase-shift in an experiment in which the skyrmion passes through a loop of a probe string. In such a setup the baryon/skyrmion number must be respected by black holes, despite the fact that it produces no long-range classical field. If initially swallowed by a black hole, the baryon number must resurface in form of a classical skyrmion hair, after the black hole evaporates below a certain critical size. Needless to say, the respect of the baryon number by black holes is expected to have potentially-interesting astrophysical consequences.

Schwinger pairs production in a soft-wall model

The Schwinger pairs production rate is calculated numerically in the soft-wall model with the help of a simpler method in determining the soft-wall's position beyond which probe strings connecting the Schwinger pairs do not fall into. Behaviours of the production rate in both the upper critical region and the middle linear part are studied carefully. The latter exhibits interesting new features un-noted previously. All results are presented in comparisons with hard-wall models.

Challenges for string cosmology

We critically assess the twin prospects of describing the observed universe in string theory, and using cosmological experiments to probe string theory. For the purposes of this short review, we focus on the limitations imposed by our incomplete understanding of string theory. After presenting an array of significant obstacles, we indicate a few areas that may admit theoretical progress in the near future.

Wilson loops in warped resolved deformed conifolds

We calculate quark–antiquark potentials using the relationship between the expectation value of the Wilson loop and the action of a probe string in the string dual. We review and categorise the possible forms of the dependence of the energy on the separation between the quarks. In particular, we examine the possibility of there being a minimum separation for probe strings which do not penetrate close to the origin of the bulk space, and derive a condition which determines whether this is the case. We then apply these considerations to the flavoured resolved deformed conifold background of Gaillard et al. (2010) [8]. We suggest that the unusual behaviour that we observe in this solution is likely to be related to the IR singularity which is not present in the unflavoured case.

Cross‐linguistic evidence for the influence of native language prosody in infant speech segmentation.

Research using artificial languages with English‐learning infants has shown both prosodic and distributional cues are used for speech segmentation by 7 months. When these cues conflict, infants younger than 7 months rely on distributional cues while older infants rely on prosodic cues). In the present study we assessed the role of prosodic information in segmentation when it is not favorably aligned with distributional cues, to determine whether language‐specific rhythmic biases guide segmentation as suggested by studies using natural speech. Two continuous streams of naturally produced syllables (English and French) were constructed using nines syllables that are permissible in both languages. Within each stream statistical cues were manipulated independently of language‐appropriate stress cues. English‐ and French‐learning 8‐month‐olds were familiarized with their native language stream and then present test probe strings to determine what syllable sequences were extracted from the stream. Probes were selected to assess the role of stress cues in segmentation. Findings show that English infants make use of a trochaic template; Canadian‐French infants show a weaker and less focused reliance on stress cues to segment words from connected speech. These cross‐linguistic differences reflect processing biases that may be set by language experience and/or elicited by speech input properties.

Type II small stringy black holes, probe branes and higher derivative interactions

The near horizon geometry of a fundamental string wrapped around an S1 reduced to four dimensions is expected to be AdS2 x S2. A probe string analysis suggests a no-force condition indicating supersymmetry, which coincides with the condition that the AdS2 is embedded in AdS3. We therefore consider the bulk string theory in terms of a WZW model on AdS3 following recent proposals by Dabholkar et. al and Giveon et. al. We find that conformal symmetry of the model naturally leads to the no-force constraints obtained from the probes. Moreover, we are able to extract the values of the moduli that account for the value of the microscopic entropy. We also investigate higher derivative corrections of the form alpha'^3 R^4 + flux terms to the horizon, in the context of type IIB supergravity. Imposing the no-force condition from the probe analysis leads to a striking simplification of the equations of motion at this order in alpha'. However, we argue that the value of the entropy can only be determined by considering all orders in alpha'.

Semi-classical probe strings on giant gravitons backgrounds

In the first part of this paper we study two $Z_2$ 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 $AdS_5\times S^5$, 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 $Z_2$ symmetry in the semi-classical closed string probes point of view.