String Mass Research Articles

High-energy γ-ray astronomy and string theory

There have been observations, first from the MAGIC Telescope (July 2005) and quite recently (September 2008) from the FERMI Satellite Telescope, on non-simultaneous arrival of high-energy photons from distant celestial sources. In each case, the highest energy photons were delayed, as compared to their lower-energy counterparts, by clearly observable time intervals. Although the astrophysics at the source of these energetic photons is still not understood, and such non simultaneous arrival might be due to non simultaneous emission as a result of conventional physics effects, nevertheless, rather surprisingly, the observed time delays can also fit excellently some scenarios in quantum gravity, predicting Lorentz violating space-time "foam" backgrounds with a non-trivial subluminal vacuum refractive index suppressed linearly by a quantum gravity scale of order of the reduced Planck mass (∼ 1018 GeV). In this talk, I discuss the MAGIC and FERMI findings in this context. First, I review the high-energy astrophysics models for cosmic acceleration at celestial sources, stressing that currently there is no consensus as regards the observed delays. Then I derive estimates/bounds on the quantum gravity scale that reproduces the observed time delays on the assumption of a vacuum refractive index for photons with linear suppression, and argue on the consistency of such bounds with measurements from other Gamma Ray Telescopes, such as H.E.S.S. I then explain under which circumstances the MAGIC and FERMI findings could be accommodated in such models in agreement with all the other, currently available, astrophysics constraints of Lorentz Violation. The key features are: (i) transparency of the foam to electrons, (ii) absence of birefringence effects and (iii) a breakdown of the local effective lagrangian formalism. In contrast to other Quantum Gravity (field-theoretic) models with non-trivial optical properties available to date, a string model based on brane-worlds with the bulk space being punctured by space-time point-like D0-brane defects, that provide the seeds for Lorentz violating foamy structures, seems to respect all three requirements. The model provides an explanation for the observed photon time delays in a natural range of the string coupling and mass scale.

Forecasting Fluctuations of Sold Industrial Production in Poland on the Basis of Electricity Demand

Abstract. The plan of the paper is as follows: introduction, section 1 with the data and econometric methodology, section 2 with empirical analysis and the model, and the conclusions. Two independent equations have been estimated. Results show that significant leading time series of sold industrial production are electricity demand in four industrial sectors: production of string mass and paper, cars and metal final goods and production of machines and electric devices.

Gregory-Laflamme instability of 5D electrically charged black strings

We study the Gregory-Laflamme instability of 5D compactified, electrically charged black strings. We consider static, linear perturbations of these solutions and derive master equation for these perturbations. Using numerical analysis we search for the threshold unstable modes and derive the critical wave-length. The results are illustrated in the black string mass v.s. electric charge phase diagram. Similar diagram is constructed using global thermodynamic equilibrium argument applied to the charged string and 5D electrically charged black hole. The results derived illustrate that electric charge makes the black string less stable.

Dynamics of strings between walls

Configurations of vortex strings stretched between or ending on domain walls were previously found to be $1/4$ Bogomol'nyi-Prasad-Sommerfield (BPS) states in $\mathcal{N}=2$ supersymmetric gauge theories in $3+1$ dimensions. Among zero modes of string positions, the center of mass of strings in each region between two adjacent domain walls is shown to be non-normalizable whereas the rests are normalizable. We study dynamics of vortex strings stretched between separated domain walls by using two methods, the moduli space (geodesic) approximation of full $1/4$ BPS states and the charged particle approximation for string end points in the wall effective action. In the first method we explicitly obtain the effective Lagrangian in the strong coupling limit, which is written in terms of hypergeometric functions, and find the 90\ifmmode^\circ\else\textdegree\fi{} scattering for head-on collision. In the second method the domain wall effective action is assumed to be $U(1{)}^{N}$ gauge theory, and we find a good agreement between two methods for well-separated strings.

Contact interactions in low scale string models with intersectingD6-branes

We evaluate the tree level four fermion string amplitudes in the TeV string mass scale models with intersecting $D6$-branes. The coefficient functions of contact interactions subsuming the contributions of string Regge resonance and winding mode excitations are obtained by subtracting out the contributions from the string massless and massive momentum modes. Numerical applications are developed for the standard-model-like solution of Cremades, Ibanez, and Marchesano for a toroidal orientifold with four intersecting $D6$-brane stacks. The chirality conserving contact interactions of the quarks and leptons are considered in applications to high-energy collider and flavor changing neutral current phenomenology. The two main free parameters consist of the string and compactification mass scales, ${m}_{s}$ and ${M}_{c}$. Useful constraints on these parameters are derived from predictions for the Bhabha scattering differential cross section and for the observables associated to the mass shifts of the neutral meson systems $K\ensuremath{-}\overline{K}$, $B\ensuremath{-}\overline{B}$, $D\ensuremath{-}\overline{D}$ and the lepton number violating three-body leptonic decays of the charged leptons $\ensuremath{\mu}$ and $\ensuremath{\tau}$.

Dijet Signals for Low Mass Strings at the Large Hadron Collider

Assuming that the fundamental string mass scale is in the TeV range and the theory is weakly coupled, we discuss possible signals of string physics at the Large Hadron Collider (LHC). In D-brane constructions, the dominant contributions to full-fledged string amplitudes for all the common QCD parton subprocesses leading to dijets are completely independent of the details of compactification, and can be evaluated in a parameter-free manner. We make use of these amplitudes evaluated near the first resonant pole to determine the discovery potential of LHC for the first Regge excitations of the quark and gluon. Remarkably, the reach of LHC after a few years of running can be as high as 6.8 TeV. Even after the first 100 pb(-1) of integrated luminosity, string scales as high as 4.0 TeV can be discovered. Data on pp-->directgamma + jet can provide corroboration for string physics at scales as high as 5 TeV.

A DNA sticker algorithm for bit-substitution in a block cipher

To attack block cipher systems, it is inevitable to handle the bit-substitutions, such as S-box, cycle left shift, and expansion substitutions. In this paper, a DNA sticker algorithm for bit-substitution such as cycle left shift is proposed. The proposed algorithm requires two equal long memory strands. The first memory strand stores the original binary string, while the second memory strand stores the resulting binary string. With the proposed algorithm, cycle left shift is performed on a mass of equal long binary strings, and the computation complexity of the cycle left shift is O ( n ) for all n -bit binary strings. Furthermore, this work indicates that block cipher systems with a 64-bit key are perhaps insecure. This paper presents clear evidence of the ability of DNA computing to perform intractable computation problems.

THE SL(2,R) WZWN STRING MODEL AS A DEFORMED OSCILLATOR AND ITS CLASSICAL-QUANTUM STRING REGIMES

We study the SL (2,R) WZWN string model describing bosonic string theory in AdS3 spacetime as a deformed oscillator together with its mass spectrum and the string modified SL (2,R) uncertainty relation. The SL (2,R) string oscillator is far more quantum (with higher quantum uncertainty) and more excited than the non-deformed one. This is accompassed by the highly excited string mass spectrum which is drastically changed with respect to the low excited one. The highly excited quantum string regime and the low excited semiclassical regime of the SL (2,R) string model are described and shown to be the quantum-classical dual of each other in the precise sense of the usual classical-quantum duality. This classical-quantum realization is not assumed nor conjectured. The quantum regime (high curvature) displays a modified Heisenberg's uncertainty relation, while the classical (low curvature) regime has the usual quantum mechanics uncertainty principle.

P-adic inflation

We construct approximate inflationary solutions rolling away from the unstable maximum of p-adic string theory, a nonlocal theory with derivatives of all orders. Novel features include the existence of slow-roll solutions even when the slow-roll parameters, as usually defined, are much greater than unity, as well as the need for the Hubble parameter to exceed the string mass scale m_s. We show that the theory can be compatible with CMB observations if g_s / \sqrt{p} ~ 10^{-7}, where g_s is the string coupling, and if m_s < 10^{-6} M_p. A red-tilted spectrum is predicted, and the scalar-to-tensor ratio is bounded from above as r < 0.006. The p-adic theory is shown to have identical inflationary predictions to a local theory with superPlanckian parameter values, but with the advantage that the p-adic theory is ultraviolet complete.

SEMICLASSICAL (QFT) AND QUANTUM (STRING) ROTATING BLACK HOLES AND THEIR EVAPORATION: NEW RESULTS

Combination of both quantum field theory (QFT) and string theory in curved backgrounds in a consistent framework, the string analogue model, allows us to provide a full picture of the Kerr–Newman black hole and its evaporation going beyond the current picture. We compute the quantum emission cross-section of strings by a Kerr–Newman black hole (KNbh). It shows the black hole emission at the Hawking temperature T sem in the early stage of evaporation and the new string emission featuring a Hagedorn transition into a string state of temperature Ts at the last stages. New bounds on J and Q emerge in the quantum string regime (besides the known ones of the classical/semiclassical QFT regime). The last state of evaporation of a semiclassical Kerr–Newman black hole with mass M &gt; m Pl , angular momentum J and charge Q is a string state of temperature Ts, string mass Ms, J = 0 and Q = 0, decaying as usual quantum strings do into all kinds of particles. (Naturally, in this framework, there is no loss of information, (there is no paradox at all).) We compute the string entropy Ss(m, j) from the microscopic string density of states of mass m and spin mode j, ρ(m, j). (Besides the Hagedorn transition at Ts) we find for high j (extremal string states j → m2α′c), a new phase transition at a temperature [Formula: see text], higher than Ts. By precisely identifying the semiclassical and quantum (string) gravity regimes, we find a new formula for the Kerr black hole entropy S sem (M, J), as a function of the usual Bekenstein–Hawking entropy [Formula: see text]. For M ≫ m Pl and J &lt; GM2/c, [Formula: see text] is the leading term, but for high angular momentum, (nearly extremal case J = GM2/c), a gravitational phase transition operates and the whole entropy S sem is drastically different from the Bekenstein–Hawking entropy [Formula: see text]. This new extremal black hole transition occurs at a temperature T sem J = (J/ℏ)T sem , higher than the Hawking temperature T sem .

Multigluon scattering in open superstring theory

We discuss the amplitudes describing $N$-gluon scattering in type I superstring theory, on a disk world sheet. After reviewing the general structure of amplitudes and the complications created by the presence of a large number of vertices at the boundary, we focus on the most promising case of maximally helicity violating (MHV) configurations because in this case, the zero Regge slope limit (${\ensuremath{\alpha}}^{\ensuremath{'}}\ensuremath{\rightarrow}0$) is particularly simple. We obtain the full-fledged MHV disk amplitudes for $N=4$, 5, and $N=6$ gluons, expressed in terms of one, two and six functions of kinematic invariants, respectively. These functions represent certain boundary integrals---generalized Euler integrals---which for $N\ensuremath{\ge}6$ correspond to multiple hypergeometric series (generalized Kamp\'e de F\'eriet functions). Their ${\ensuremath{\alpha}}^{\ensuremath{'}}$ expansions lead to Euler-Zagier sums. For arbitrary $N$, we show that the leading string corrections to the Yang-Mills amplitude, of order $\mathcal{O}({\ensuremath{\alpha}}^{\ensuremath{'}2})$, originate from the well-known ${\ensuremath{\alpha}}^{\ensuremath{'}2}\text{ }\mathrm{Tr}{F}^{4}$ effective interactions of four gauge field strength tensors. By using iteration based on the soft gluon limit, we derive a simple formula valid to that order for arbitrary $N$. We argue that such a procedure can be extended to all orders in ${\ensuremath{\alpha}}^{\ensuremath{'}}$. If nature gracefully picked a sufficiently low string mass scale, our results would be important for studying string effects in multijet production at the Large Hadron Collider (LHC).

Integrable structure of the field theory of open superstrings

We find asymptotic expansions in the “string mass” μ for μ-deformed Γ-functions and Neumann coefficients characterizing the three-string vertex in the light-cone gauge of the field theory of open superstrings on a maximally supersymmetric pp-wave background.

Finding submasses in weighted strings with Fast Fourier Transform

We study the Submass Finding Problem: given a string s over a weighted alphabet, i.e., an alphabet Σ with a weight function μ : Σ → N , we refer to a mass M ∈ N as a submass of s if s has a substring whose weights sum up to M. Now, for a set of input masses { M 1 , … , M k } , we want to find those M i which are submasses of s, and return one or all occurrences of substrings with mass M i . We present efficient algorithms for both the decision and the search problem. Furthermore, our approach allows us to compute efficiently the number of different submasses of s. The main idea of our algorithms is to define appropriate polynomials such that we can determine the solution for the Submass Finding Problem from the coefficients of the product of these polynomials. We obtain very efficient running times by using Fast Fourier Transform to compute this product. Our main algorithm for the decision problem runs in time O ( μ s log μ s ) , where μ s is the total mass of string s. Employing methods for compressing sparse polynomials, this runtime can be viewed as O ( σ ( s ) log 2 σ ( s ) ) , where σ ( s ) denotes the number of different submasses of s. In this case, the runtime is independent of the size of the individual masses of characters.

Noncommutative Kachru-Kallosh-Linde-Maldacena-McAllister-Trivedi model

In the noncommutative spacetime the fine tuning in KKLMMT model can be significantly released and a nice running of spectral index fitting the WMAP 3 yr data can be achieved. The fitting results show that the noncommutative mass scale is roughly $5\ifmmode\times\else\texttimes\fi{}{10}^{14}\text{ }\text{ }\mathrm{Gev}$. The string mass scale is higher than the noncommutative scale unless the string coupling is smaller than ${10}^{\ensuremath{-}10}$.

MONTE CARLO STUDY OF GLUEBALL MASSES IN THE HAMILTONIAN LIMIT OF SU(3) LATTICE GAUGE THEORY

Using Standard Euclidean Monte Carlo techniques, we discuss in detail the extraction of the glueball masses of four-dimensional SU(3) lattice gauge theory in the Hamiltonian limit, where the temporal lattice spacing is zero. By taking into account the renormalization of both the anisotropy and the Euclidean coupling, we calculate the string tension and masses of the scalar, axial vector and tensor states using standard Wilson action on increasingly anisotropic lattices, and make an extrapolation to the Hamiltonian limit. The results are compared with estimates from various other Hamiltonian and Euclidean studies. We find that more accurate determination of the glueball masses and the mass ratios has been achieved in the Hamiltonian limit and the results are a significant improvement upon previous Hamiltonian estimates. The continuum predictions are then found by extrapolation of results obtained from smallest values of spatial lattice spacing. For the lightest scalar, tensor and axial vector states we obtain masses of m0++ = 1654±83 MeV , m2++ = 2272±115 MeV and m1+- = 2940±165 MeV , respectively. These are consistent with the estimates obtained in the previous studies in the Euclidean limit. The consistency is a clear evidence of universality between Euclidean and Hamiltonian formulations. From the accuracy of our estimates, we conclude that the standard Euclidean Monte Carlo method is a reliable technique for obtaining results in the Hamiltonian version of the theory, just as in Euclidean case.

Erratum: Bounds on cosmic strings from WMAP and SDSS [Phys. Rev. D72, 23513 (2005)

We find the constraints from WMAP and SDSS data on the fraction of cosmological fluctuations sourced by local cosmic strings using a Markov Chain Monte Carlo (MCMC) analysis. In addition to varying the usual 6 cosmological parameters and the string tension ($\mu$), we also varied the amount of small-scale structure on the strings. Our results indicate that cosmic strings can account for up to 7 (14)% of the total power of the microwave anisotropy at 68 (95)% confidence level. The corresponding bound on the string mass per unit length, within our string model, is $G\mu < 1.8 (2.7) \times 10^{-7}$ at 68 (95)% c.l., where this constraint has been altered from what appears below following the correction of errors in our cosmic string code outlined in a recent erratum, astro-ph/0604141. We also calculate the B-type polarization spectra sourced by cosmic strings and discuss the prospects of their detection.

Fractal properties and small-scale structure of cosmic string networks

We present results from a detailed numerical study of the small-scale and loop production properties of cosmic string networks, based on the largest and highest resolution string simulations to date. We investigate the nontrivial fractal properties of cosmic strings, in particular, the fractal dimension and renormalized string mass per unit length, and we also study velocity correlations. We demonstrate important differences between string networks in flat (Minkowski) spacetime and the two very similar expanding cases. For high resolution matter era network simulations, we provide strong evidence that small-scale structure has converged to ``scaling'' on all dynamical length scales, without the need for other radiative damping mechanisms. We also discuss preliminary evidence that the dominant loop production size is also approaching scaling.

Light-cone superstring field theory, pp-wave background and integrability properties

We show that the three-string vertex coefficients in light-cone open string field theory satisfy the Hirota equations for the dispersionless Toda lattice hierarchy. We show that Hirota equations allow us to calculate the correlators of an associated quantum system where the Neumann coefficients represent the two-point functions. We consider next the three-string vertex coefficients of the light-cone string field theory on a maximally supersymmetric pp-wave background. Using the previous results, we are able to show that these Neumann coefficients satisfy the Hirota equations for the full Toda lattice hierarchy at least up to second order in the ‘string mass’ μ.

(A)symmetric tachyon rolling in de Sitter spacetime: A universe devoid of Planck density

In a recent paper we studied rolling tachyon flat FRW cosmologies, but those admitting only time-reversal asymmetric boundary conditions. The time-reversal symmetric cosmologies have been studied by Sen previously. We show explicitly here that through appropriate choice of initial conditions, the time evolution of the Hubble parameter in these two types of solutions can be made completely identical for t>0, except near t=0. The rolling tachyon solution also gives rise to necessary inflation. We find that universe does start as a string size object (with string scale 1015 GeV) with a string mass density ρs≃1078 gmcm−3 and not with Planck density.

Bounds on cosmic strings from WMAP and SDSS

We find the constraints from Wilkinson microwave anisotropy probe (WMAP) and Sloan digital sky survey (SDSS) data on the fraction of cosmological fluctuations sourced by local cosmic strings using a Markov Chain Monte Carlo (MCMC) analysis. In addition to varying the usual 6 cosmological parameters and the string tension ($\ensuremath{\mu}$), we also varied the amount of small-scale structure on the strings. Our results indicate that cosmic strings can account for up to 7 (14)% of the total power of the microwave anisotropy at 68 (95)% confidence level. The corresponding bound on the string mass per unit length, within our string model, is $G\ensuremath{\mu}&lt;3.4(5)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}7}$ at 68 (95)% C.L. We also calculate the $B$-type polarization spectra sourced by cosmic strings and discuss the prospects of their detection.