Foliations and 2+1 Causal Dynamical Triangulation Models

The original models of causal dynamical triangulations construct space-time by arranging a set of simplices in layers separated by a fixed time-like distance. The importance of the foliation structure in the 2+1 dimensional model is studied by considering variations in which this property is relaxed. It turns out that the fixed-lapse condition can be equivalently replaced by a set of global constraints that have geometrical interpretation. On the other hand, the introduction of new types of simplices that puncture the foliating sheets in general leads to different low-energy behavior compared to the original model.Comment: v2: 9 pages, 3 figures, published versio

The S-Matrix of superstring field theory

We show that the classical S-matrix calculated from the recently proposed superstring field theories give the correct perturbative S-matrix. In the proof we exploit the fact that the vertices are obtained by a field redefinition in the large Hilbert space. The result extends to include the NS-NS subsector of type II superstring field theory and the recently found equations of motions for the Ramond fields. In addition, our proof implies that the S-matrix obtained from Berkovits' WZW-like string field theory then agrees with the perturbative S-matrix to all orders.Comment: 19 pages, 2 figure

Quantum vacuum effects from boundaries of designer potentials

Vacuum energy in quantum field theory, being the sum of zero-point energies of all field modes, is formally infinite but yet, after regularization or renormalization, can give rise to finite observable effects. One way of understanding how these effects arise is to compute the vacuum energy in an idealized system such as a large cavity divided into disjoint regions by pistons. In this paper, this type of calculation is carried out for situations where the potential affecting a field is not the same in all regions of the cavity. It is shown that the observable parts of the vacuum energy in such potentials do not fall off to zero as the region where the potential is nontrivial becomes large. This unusual behavior might be interesting for tests involving quantum vacuum effects and for studies on the relation between vacuum energy in quantum field theory and geometry.Comment: 13 pages, 2 figure

Planning ahead: How recent experience with structures and words changes the scope of linguistic planning

The scope of linguistic planning, i.e., the amount of linguistic information that speakers prepare in advance for an utterance they are about to produce, is highly variable. Distinguishing between possible sources of this variability provides a way to discriminate between production accounts that assume structurally incremental and lexically incremental sentence planning. Two picture-naming experiments evaluated changes in speakers’ planning scope as a function of experience with message structure, sentence structure, and lexical items. On target trials participants produced sentences beginning with two semantically related or unrelated objects in the same complex noun phrase. To manipulate familiarity with sentence structure, target displays were preceded by prime displays that elicited the same or different sentence structures. To manipulate ease of lexical retrieval, target sentences began either with the higher-frequency or lower-frequency member of each semantic pair. The results show that repetition of sentence structure can extend speakers’ scope of planning from one to two words in a complex noun phrase, as indexed by the presence of semantic interference in structurally primed sentences beginning with easily retrievable words. Changes in planning scope tied to experience with phrasal structures favor production accounts assuming structural planning in early sentence formulation

Vertical Integration from the Large Hilbert Space

We develop an alternative description of the procedure of vertical integration based on the observation that amplitudes can be written in BRST exact form in the large Hilbert space. We relate this approach to the description of vertical integration given by Sen and Witten.Comment: V2: 28 pages, 5 figures. Minor correction

Entangling Atoms in Photonic Crystals

We propose a method for entangling a system of two-level atoms in photonic crystals. The atoms are assumed to move in void regions of a photonic crystal. The interaction between the atoms is mediated either via a defect mode or via resonant dipole-dipole interaction. We show that these interactions can produce pure entangled atomic states. We analyze the problem with parameters typical for currently existing photonic crystals and Rydberg atoms. We show that the atoms can emerge from photonic crystals in entangled states. Depending on the linear dimensions of the crystal and on their velocity of the entangled atoms can be separated by tens of centimeters.Comment: 9 pages, revtex, 6 figur

Open Superstring Field Theory on the Restricted Hilbert Space

Recently an action for open superstring field theory was proposed where the Neveu-Schwarz sector is formulated in the large Hilbert space while the Ramond sector lives in a restriction of the small Hilbert space. The purpose of this note is to clarify the relation of the restricted Hilbert space with other approaches and to formulate open superstring field theory entirely in the small Hilbert space.Comment: 10 page