arXiv subjects

Konstantin G. Savvidy

Publications and source records attributed to Konstantin G. Savvidy.

13 recordsLinked to original sources

arXiv2018

A Priori Tests for the MIXMAX Random Number Generator

We define two a priori tests of pseudo-random number generators for the class of linear matrix-recursions. The first desirable property of a random number generator is the smallness of serial or lagged correlations between generated numbers. For the particular matrix generator called MIXMAX, we find that the serial correlation actually vanishes. Next, we define a more sophisticated measure of correlation, which is a multiple correlator between elements of the generated vectors. The lowest order non-vanishing correlator is a four-element correlator and is non-zero for lag $s=1$. At lag $s \ge 2$, this correlator again vanishes. For lag $s=2$, the lowest non-zero correlator is a six-element correlator. The second desirable property for a linear generator is the favorable structure of the lattice which typically appears in dimensions higher than the dimension of the phase space of the generator, as discovered by Marsaglia. We define an appropriate generalization of the notion of the spectral index for LCG which is a measure of goodness of this lattice to the matrix generators such as MIXMAX and find that the spectral index is independent of the size of the matrix N and is equal to $\sqrt{3}$.

physics.data-an↗

arXiv2014

The MIXMAX random number generator

In this note, we give a practical solution to the problem of determining the maximal period of matrix generators of pseudo-random numbers which are based on an integer-valued unimodular matrix of size NxN known as MIXMAX and arithmetic defined on a Galois field GF[p] with large prime modulus p. The existing theory of Galois finite fields is adapted to the present case, and necessary and sufficient condition to attain the maximum period is formulated. Three efficient algorithms are presented. First, allowing to compute the multiplication by the MIXMAX matrix with O(N) operations. Second, to recursively compute the characteristic polynomial with O(N^2) operations, and third, to apply skips of large number of steps S to the sequence in O(N^2 log(S)) operations. It is demonstrated that the dynamical properties of this generator dramatically improve with the size of the matrix N, as compared to the classes of generators based on sparse matrices and/or sparse characteristic polynomials. Finally, we present the implementation details of the generator and the results of rigorous statistical testing.

hep-lat↗

arXiv2012

Direct Dark Matter Detection - A spin 3/2 WIMP candidate

We consider a Dark Matter candidate particle of spin 3/2 with neutrino-like Standard Model strength interactions. In the Majorana case, the particle can account for all of the Dark Matter for a range of masses between 70-160 GeV, depending on the strength of the Higgs couplings. The elementary spin-dependent cross section on the nucleon is calculated to be 1.7 x 10^-2 pb, and does not depend on the mass or any additional parameters. The Dirac case is excluded by the very large coherent cross section. The amplitude at the nuclear level is of the purely isovector form. We make detailed predictions for differential and total rates of scattering on a variety of nuclear targets of interest to the current direct detection experiments. For heavy targets the annual modulation amplitude is predicted to be negative, which may help to determine the mass of the WIMP if and when data become available.

hep-ph↗

arXiv2012

Spinor formalism for massive fields with half-integral spin

In this article, we extend the %Weyl-van der Waerden spinor technique for calculating helicity amplitudes to general massive fields of half-integer spins. We find that the little group generators can be represented as first-order differential operators in the spinor formalism. We use the spinor forms of the generators to get the explicit form of the massive fields of any spin and any helicity. We also deal with the three-particle S-matrix by these spinor form generators, and find that we are able to extend the explicit form of the three-particle vertex obtained by Benincasa and Cachazo to the massive case. We present the explicit expressions for the amplitudes with external particles of the lowest helicities up to -3/2. Group theory, in the form of raising operators of the little group, then dictates other amplitudes with higher helicity in the same spin multiplets. The formalism allows, in principle, to determine the electromagnetic form-factors of charged particles of arbitrary helicities, without additional assumptions about the underlying lagrangian. We find that restrictions which follow from gauge and Lorentz invariance are nearly as restrictive as in the massless case.

hep-th↗

arXiv2011

Quantum electrodynamics of spin 3/2, II

Electromagnetic interactions of the spin 3/2 particle are investigated while allowing the propagation of the transverse spin 1/2 component present in the reducible Rarita-Schwinger vector-spinor. This is done by allowing a more general form for the mass term, while leaving the kinetic terms untouched. We find that the interaction is consistent and does not lead to superluminal propagation for a range of the mass of the spin 1/2 particle, except for the special point where the spin 1/2 particle is infinitely massive. We then quantize the theory using the appropriate Grassmann-variable path integral and study the poles of the propagator. The unfamiliar feature of the theory is that the charge matrix is not positive definite; it is positive definite on the space of spin 3/2 solutions, and negative definite on the space of spin 1/2 solutions. Classically, for spin 1/2 modes the energy is of the opposite sign to frequency, i.e. the positive frequency modes have negative energy. It is found that the retarded part appropriately propagates the positive energy solutions forward in time, while the advanced part propagates the negative energy solutions back in time so long as the free parameter is chosen such that the positive frequency modes have the same parity. The propagator contains poles of the spin 1/2 modes above the real axis for the positive and below the real axis for the negative frequency modes, while the residues at those poles are also of the sign opposite to the usual; altogether this leads to a unitary S-matrix, the forward amplitude being positive for all modes. The canonically quantized field is causal, and the equal-time anti-commutator has positive definite form. We choose the physical vacuum as the highest-weight state with respect to the spin 1/2 operators in order to have positive energy, and to correctly reproduce both the unusual residues and locations of the poles.

hep-th↗

arXiv2010

Quantum electrodynamics of spin 3/2

Electromagnetic interactions of the spin 3/2 particle are investigated while allowing the propagation of the transverse spin 1/2 component present in the reducible Rarita-Schwinger vector-spinor. This is done by allowing a more general form for the mass term, while leaving the kinetic terms untouched. We find that the interaction is consistent and does not lead to superluminal propagation for a range of the mass parameter where the spin 1/2 component is lighter than the spin 3/2 component, in contrast to the traditional value whereby the spin 1/2 component is removed by making it infinitely massive. The hyperbolicity condition is found to be independent of the magnitude of the electromagnetic field, and the canonically quantized field is constructed to be causal. We then provide appropriate projection operators which reproduce the spin-sum expressions and enable the construction of a physically acceptable propagator. Finally, we suggest a scheme for extension of the Standard Model with Rarita-Schwinger multiplets and identify the muon as the spin 1/2 component of the new multiplet which in addition contains a new, heavy partner of the muon of spin 3/2. The scattering cross-section e+, e- \to μ+, μ- is calculated within this theory, compared to QED, and finally a bound on the new particle's mass is obtained from precision electroweak measurements.

hep-th↗

arXiv2000

Ramond-Ramond Field Radiation from Rotating Ellipsoidal Membranes

We find a new stable rotator solution in D0-brane matrix mechanics. The solution is interpreted as a D2/D0 brane bound state, constructed as a transversely rotating ellipsoidal membrane with N D0-branes pinned over it. From the membrane point of view the attractive force of tension is exactly cancelled by the repulsive centrifugal force. Dynamical properties of the system are investigated, in particular the emission of spherical waves in the different massless sectors of supergravity. We compute the RR 1-form quadrupole, the RR 3-form dipole and the gravitational quadrupole radiation. Also, we show that our non-singular classical solution is stable against small perturbations in the initial conditions. Furthermore, we comment on a possible fundamental particle interpretation of our system.

hep-th↗

arXiv2000

Stability of the Rotating Ellipsoidal D0-brane System

In this note we prove the complete stability of the classical fluctuation modes of the rotating ellipsoidal membrane. The analysis is carried out in the full SU(N) setting, with the conclusion that the fluctuation matrix has only positive eigenvalues. This proves that the solution will remain close to the original one for all time, under arbitrary infinitesimal perturbations of the gauge fields.

hep-th↗

arXiv2000

The Discrete Bound State Spectrum of the Rotating D0-brane System

In this note we obtain the discrete spectrum of the rotating ellipsoidal membrane, the solution to classical equations of motion in the matrix mechanics of N D0-branes. This solution has the interpretation of a closed D2-brane with the D0-branes bound to its surface. The semi-classical quantization is performed on the rotational modes with the result that both radii and energy are quantized. We also argue that the quantum mechanics of this system is well defined, with a unique ground state of positive energy in each sector with a non-zero angular momentum. The scaling of the size and energy of these states allows us to identify our rotating brane excited states with the previously conjectured resonances in the scattering of D0-branes.

hep-th↗

arXiv1999

Born-Infeld Action in String Theory

In this thesis I present applications of the Born-Infeld action to the description of D-branes, mostly in the context of type IIB string theory. First I present the Callan-Maldacena construction of a fundamental string attached to a threebrane, whereby the string is made out of the wrapped brane. This interpretation withstands a rather detailed scrutiny, including the magnitude of the static tension and of the B-I charge; and Polchinski's mixed Dirichlet/Neumann boundary conditions for small perturbations of the string. The latter arise dynamically from the full non-linear equations of motion. Also, the Born-Infeld charge is shown to produce the correct form of dipole radiation under the influence of harmonic oscillations of the string. The second part comprises of the application of these ideas to the AdS/CFT correspondence. Using the essentially non-perturbative nature of the B-I action we were able to construct in the near-horizon geometry of N D3-branes the color-singlet baryon vertex of the SU(N) gauge theory as a fivebrane wrapped on the $S^5$ sphere, with B-I strings playing the role of the quarks. Also, in the asymptotically flat background we obtain a smooth classical description of the Hanany-Witten phenomenon. In the case of non-extremal background we construct baryons of the three-dimensional non-supersymmetric theory, the low energy dynamics of which was conjectured to be equivalent to ordinary QCD. Our approach allows to exhibit confining properties of color flux tubes, i.e. the dependence of the tension of the flux tube on its color content. We do this by building an extended baryon, where a fraction $ν$ of the total of N quarks is removed to a finite distance.

hep-th↗

arXiv1999

Baryons and Flux Tubes in Confining Gauge Theories from Brane Actions

We study baryon configurations in large N non-supersymmetric SU(N) gauge theories, applying the AdS/CFT correspondence. Using the D5-brane worldvolume theory in the near-horizon geometry of non-extremal D3-branes, we find embeddings which describe baryonic states in three-dimensional QCD. In particular, we construct solutions corresponding to a baryon made of N quarks, and study what happens when some fraction $ν$ of the total number of quarks are bodily moved to a large spatial separation from the others. The individual clumps of quarks are represented by Born-Infeld string tubes obtained from a D5-brane whose spatial section has topology $R \times S^4$. They are connected by a confining color flux tube, described by a portion of the fivebrane that runs very close and parallel to the horizon. We find that this flux tube has a tension with a nontrivial $ν$-dependence (not previously obtained by other methods). A similar picture is presented for the four-dimensional case.

hep-th↗

arXiv1998

Brane Death via Born-Infeld String

I revisit the solution of Born-Infeld theory which corresponds to a 3-brane and anti-brane joined by a (fundamental) string. The global instability of this configuration makes possible the semiclassical tunneling into a wide, short tube which keeps expanding out, thus annihilating the brane . This tunneling is suppressed exponentially as $\exp(- S_{cl}/g)$. The attraction between the branes causes them to approach and at some point to tunnel, because the action of the bounce solution goes to zero. The energy of the solution at the top of the barrier, the sphaleron, goes like $\sim D^3$ for large separarions D, while the energy of the string is proportional to its length D.

hep-th↗

arXiv1998

Baryons and String Creation from the Fivebrane Worldvolume Action

We construct BPS-exact solutions of the worldvolume Born-Infeld plus WZW action of a D5-brane in the background of N D3-branes. The non-trivial background metric and RR five-form field strength play a crucial role in the solution. When a D5-brane is dragged across a stack of N D3-branes a bundle of N fundamental strings joining the two types of branes is created, as in the Hanany-Witten effect. Our solutions give a detailed description of this bundle in terms of a D5-brane wrapped on a sphere. We discuss extensions of these solutions which have an interpretation in terms of gauge theory multi-quark states via the AdS/CFT correspondence.

hep-th↗