Elementary Strings Research Articles

What is the magnetic Weak Gravity Conjecture for axions?

The electric Weak Gravity Conjecture demands that axions with large decay constant f couple to light instantons. The resulting large instantonic corrections pose problems for natural inflation. We explore an alternative argument based on the magnetic Weak Gravity Conjecture for axions, which we try to make more precise. Roughly speaking, it demands that the minimally charged string coupled to the dual 2‐form‐field exists in the effective theory. Most naively, such large‐f strings curve space too much to exist as static solutions, thus ruling out large‐f axions. More conservatively, one might allow non‐static string solutions to play the role of the required charged objects. In this case, topological inflation would save the superplanckian axion. Furthermore, a large‐f axion may appear in the low‐energy effective theory based on two subplanckian axions in the UV. The resulting effective string is a composite object built from several elementary strings and domain walls. It may or may not satisfy the magnetic Weak Gravity Conjecture depending on how strictly the latter is interpreted and on the cosmological dynamics of this composite object, which remain to be fully understood. Finally, we recall that large‐field brane inflation is naively possible in the codimension‐one case. We show how string‐theoretic back‐reaction closes this apparent loophole of large‐f (non‐periodic) pseudo‐axions.

Elementary supramolecular strings in solutions of chiral trifluoroacetylated amino alcohols

IR spectroscopy is applied to studying the effect of nonpolar and low-polar solvents on the molecular structure of solid-state quasi-one-dimensional strings formed through the chiral self-assembly from solutions of trifluoroacetylated homochiral amino alcohols (TFAAA). It is experimentally confirmed that in stable two-phase string/solvent gels and respective xerogels, solid-phase strings contain no solvent molecules as a structural element, experiencing, however, a weak disturbing influence of solvent molecules. It is shown that the process of spontaneous self-assembly of chiral strings in solutions is accompanied by the formation of a complex system of hydrogen bonds involving the C=O, N–H, and O–H functional groups of dissolved TFAAA molecules and by the displacement of solvent molecules to the periphery of the resulting quasi-one-dimensional strings. The results of the present work, together with data obtained by other experimental methods, indicate that TFAAA-based elementary strings have diameters of 1–2 nm, being crystalline, molecularly thin, quasi-one-dimensional objects. The amplitude of the thermally activated bending vibrations (transverse phonons) of elementary strings is sufficient to cause the entanglement of elementary strings, which leads to the formation of larger diameter supercoiled strings.

Structural transitions in chiral solutions and a microscopic model of a chiral string

Homochiral solutions of trifluoroacetylaminoalcohols (TFAAAs) are investigated. It is established that TFAAA molecules aggregate into submicroscopic string with long-range order and helical symmetry, followed by successive formation, through supercoiling, of alternating chiral phases (elementary strings combine into microscopic due to the van der Waals interaction), observed as a structural transition with a width of 20–40°C. A microscopic model of a string is proposed, which takes into account that the stereospecificity of the multicenter interaction (complementarity) imposed by chirality leads to a stacking compact molecular packing (submicroscopic or elementary) of strings with a long-range order.

Quantum fusion of strings (flux tubes) and domain walls

We consider formation of composite strings and domain walls as a result of fusion of two elementary objects (elementary strings in the first case and elementary walls in the second) located at a distance from each other. The tension of the composite object T_2 is assumed to be less than twice the tension of the elementary object T_1, so that bound states are possible. If in the initial state the distance d between the fusing strings or walls is much larger than their thickness and satisfies the conditions T_1 d^2 >> 1 (in the string case) and T_1 d^3 >> 1 (in the wall case), the problem can be fully solved quasiclassically. The fusion probability is determined by the first, "under the barrier" stage of the process. We find the bounce configuration and its extremal action S_B. In the wall problem e^{-S_B} gives the fusion probability per unit time per unit area. In the string case, due to a logarithmic infrared divergence, the problem is well formulated only for finite-length strings. The fusion probability per unit time can be found in the limit in which the string length is much larger than the distance between two merging strings.

String Instrument Education Made Possible: Cross Timbers Youth Orchestra Elementary Strings Brings Music to Parents' Ears

String Instrument Education Made Possible: Cross Timbers Youth Orchestra Elementary Strings Brings Music to Parents' Ears

Black holes, elementary strings and holomorphic anomaly

In a previous paper we had proposed a specific route to relating the entropy of two charge black holes to the degeneracy of elementary string states in N=4 supersymmetric heterotic string theory in four dimensions. For toroidal compactification this proposal works correctly to all orders in a power series expansion in inverse charges provided we take into account the corrections to the black hole entropy formula due to holomorphic anomaly. In this paper we demonstrate that similar agreement holds also for other N=4 supersymmetric heterotic string compactifications.

Scattering of zero-branes off elementary strings in Matrix theory

We consider the scattering of zero-branes off an elementary string in Matrix theory or equivalently gravitons off a longitudinally wrapped membrane. The leading supergravity result is recovered by a one-loop calculation in zero-brane quantum mechanics. Simple scaling arguments are used to show that there are no further corrections at higher loops, to the leading term in the large impact parameter, low velocity expansion. The mechanism for this agreement is identified in terms of properties of a recently discovered boundary conformal field theory.

Branes, orientifolds and the creation of elementary strings

The potential of a configuration of two Dirichlet branes for which the number of ND-directions is eight is determined. Depending on whether one of the branes is an anti-brane, the potential vanishes or is twice as large as the dilaton-gravitational potential. This is shown to be related to the fact that a fundamental string is created when two such branes cross. Special emphasis is given to the D0–D8 system, for which an interpretation of these results in terms of the massive IIA supergravity is presented. It is also shown that the branes cannot move non-adiabatically in the transverse direction. The configuration of a zero-brane and an orientifold 8-plane is analyzed in a similar way, and the implications for the type IA-heterotic duality and the heterotic matrix theory are discussed.

A general-purpose signal processor architecture for neurocomputing and preprocessing applications

A general-purpose Neural Signal Processor MA16 is presented the architecure of which is guided by an analysis of today's neural algorithms. The MA16 executes the elementary algorithmic strings which are compute-bound and shared by all neural nets; operations which are not time consuming are let to hardware off-the-shelf. Digital design is chosen because of flexibility and computation accuracy. The throughput is 800 million connections per second at a clock frequency of 50 MHz (1 connection = 16 bit). This performance is valid for arbitrary networks provided they consist of more than 16 neurons each comprising more than 16 synapses. Depending on the needs of the application under consideration a linear or 2-dimensional array of VLSI chips can be constructed in order to provide sufficient processing power and weight memory.

A new model for hadronization and e +e − annihilation

A new string/cluster model for e +e − annihilation is presented. Event evolution is described using a simple, 3-stage formalism: (i) coherent parton shower generation, (ii) evolution of elementary strings formed from the parton final state, and (iii) parameterized hadronization of small mass clusters formed during string evolution. Significant improvements over previous cluster models arise from the use of full, massless relativistic string motion in the second stage of the model, so that the formalism is naturally insensitive to soft perturbative radiation. Parameter fitting and sensitivity of model predictions to variations in the cluster formation parameters are discussed in detail. The model is shown to reproduce a variety of e +e − annihilation data over a wide range of E CM. Specific suggestions are made for future improvements in the perturbative QCD and cluster decay stages of the model.

Stability in OL systems

Some properties of recurrent strings with respect to an OL scheme and an OL system are discussed. A recurrent string is factorized into some elementary recurrent strings. The two decision problems are shown to be decidable: One is whether or not a given string is recurrent with respect to an OL scheme. The other is whether or not a given OL language contains some recurrent strings.