18 research outputs found
Finite Black Hole Entropy and String Theory
An accelerating observer sees a thermal bath of radiation at the Hawking
temperature which is proportional to the acceleration. Also, in string theory
there is a Hagedorn temperature beyond which one cannot go without an infinite
amount of energy. Several authors have shown that in the context of Hawking
radiation a limiting temperature for string theory leads to a limiting
acceleration, which for a black hole implies a minimum distance from the
horizon for an observer to remain stationary. We argue that this effectively
introduces a cutoff in Rindler space or the Schwarzschild geometry inside of
which accelerations would exceed this maximum value. Furthermore, this natural
cutoff in turn allows one to define a finite entropy for Rindler space or a
black hole as all divergences were occurring on the horizon. In all cases if a
particular relationship exists between Newton's constant and the string tension
then the entropy of the string modes agrees with the Bekenstein-Hawking
formula.Comment: 17 pages, 1 figure, Florida Preprint UFIFT-HEP-94-0
Bethe Ansatz solution of the open XXZ chain with nondiagonal boundary terms
We propose a set of conventional Bethe Ansatz equations and a corresponding
expression for the eigenvalues of the transfer matrix for the open spin-1/2 XXZ
quantum spin chain with nondiagonal boundary terms, provided that the boundary
parameters obey a certain linear relation.Comment: 11 pages, LaTeX; amssymb, amsmath, no figures; v2: citation adde
On the spin-liquid phase of one dimensional spin-1 bosons
We consider a model of one dimensional spin-1 bosons with repulsive
density-density interactions and antiferromagnetic exchange. We show that the
low energy effective field theory is given by a spin-charge separated theory of
a Tomonaga-Luttinger Hamiltonian and the O(3) nonlinear sigma model describing
collective charge and spin excitations respectively. At a particular ratio of
the density-density to spin-spin interaction the model is integrable, and we
use the exact solutions to provide an independent derivation of the low energy
effective theory. The system is in a superfluid phase made of singlet pairs of
bosons, and we calculate the long-distance asymptotics of certain correlation
functions.Comment: 17 page
Neutrino Zero Modes on Electroweak Strings
Zero modes of massive standard model fermions have been found on electroweak
Z-strings. A zero mode solution for a massless left-handed neutrino is also
known, but was thought to be non-normalizable. Here we show that although this
mode is not discretely normalizable, it is delta-function normalizable and the
correct interpretation of this solution is within the framework of the
continuum spectrum. We also analyze an extension of the standard model
including right-handed neutrinos in which neutrinos have Dirac masses, arising
from a Yukawa coupling to the usual SU(2) Higgs doublet, and right-handed
Majorana masses. The Majorana mass terms are taken to be spatially homogeneous
and are presumed to arise from the vacuum expectation value of some field
acquired in a phase transition well above the electroweak phase transition. The
resulting zero energy equations have a discrete zero mode.Comment: 5 pages, 1 figures, version to appear in Phys. Rev.
Exact Spectral Gaps of the Asymmetric Exclusion Process with Open Boundaries
We derive the Bethe ansatz equations describing the complete spectrum of the
transition matrix of the partially asymmetric exclusion process with the most
general open boundary conditions. By analysing these equations in detail for
the cases of totally asymmetric and symmetric diffusion, we calculate the
finite-size scaling of the spectral gap, which characterizes the approach to
stationarity at large times. In the totally asymmetric case we observe boundary
induced crossovers between massive, diffusive and KPZ scaling regimes. We
further study higher excitations, and demonstrate the absence of oscillatory
behaviour at large times on the ``coexistence line'', which separates the
massive low and high density phases. In the maximum current phase, oscillations
are present on the KPZ scale . While independent of the
boundary parameters, the spectral gap as well as the oscillation frequency in
the maximum current phase have different values compared to the totally
asymmetric exclusion process with periodic boundary conditions. We discuss a
possible interpretation of our results in terms of an effective domain wall
theory.Comment: 42 pages, 25 figures; added appendix and minor correction
Sigma models as perturbed conformal field theories
We show that two-dimensional sigma models are equivalent to certain perturbed
conformal field theories. When the fields in the sigma model take values in a
space G/H for a group G and a maximal subgroup H, the corresponding conformal
field theory is the limit of the coset model , and the
perturbation is related to the current of G. This correspondence allows us for
example to find the free energy for the "O(n)" (=O(n)/O(n-1)) sigma model at
non-zero temperature. It also results in a new approach to the CP^{n} model.Comment: 4 pages. v2: corrects typos (including several in the published
version
Integrable Ladder t-J Model with Staggered Shift of the Spectral Parameter
The generalization of the Yang-Baxter equations (YBE) in the presence of Z_2
grading along both chain and time directions is presented and an integrable
model of t-J type with staggered disposition along a chain of shifts of the
spectral parameter is constructed. The Hamiltonian of the model is computed in
fermionic formulation. It involves three neighbour site interactions and
therefore can be considered as a zig-zag ladder model. The Algebraic Bethe
Ansatz technique is applied and the eigenstates, along with eigenvalues of the
transfer matrix of the model are found. In the thermodynamic limit, the lowest
energy of the model is formed by the quarter filling of the states by fermions
instead of usual half filling.Comment: Latex2e with amsfonts package; 16 page
Virtual Asisten Pusat Informasi Mahasiswa Berbasis Android Menggunakan Flutter
Penelitian ini bertujuan untuk merancang chatbot virtual asisstant pusat informasi mahasiswa pada Universitas Ibnu Sina Fakultas Teknik prodi Teknik Informatika. Pemodelan yang digunakan yaitu Flowchart dan Data Flow Diagram (DFD), sedangkan untuk pengembangan sistem penelitian yaitu Waterfall dengan tahapan Analisis, Desain, Kode Program, Pengujian, dan Pemeliharaan. Chatbot dirancang berbasis Android dan Website dengan menggunakan Flutter yang berfungsi sebagai media percakapan dengan fitur webview, sedangkan untuk tampilan percakapan menggunakan Framework Bootstrap. Hasil penelitian ini adalah adanya chatbot yang bisa melakukan percakapan mengenai informasi umum mahasiswa dengan bot yang berbasis teks, dan juga bisa melakukan interaksi dengan menekan tombol chip atau card menu, dengan adanya chatbot ini diharapkan memudahkan mahasiswa untuk mendapatkan informasi secara cepat tanpa kendala
The Effectiveness of Learning Media as A Supporter of Online Learning in Computer Networking Courses
With the issuance of a study from home policy by the government during the COVID-19 pandemic, the learning process is carried out online. this makes lecturers innovate in using learning media in the learning process. The lack of use of learning media during the COVID-19 pandemic resulted in students being less motivated and having low learning enthusiasm in the computer network learning process. To overcome this problem, one alternative is to develop learning media in the pandemic era. The purpose of this study is to test the effectiveness of the media developed to support the online learning process. The research method of developing learning media used is Research and Development (R&D) using the Instructional Development Institute (IDI) model approach. The IDI approach model includes three stages, namely define, develop, and evaluate. The effectiveness test is carried out at the evaluation stage by treating the control class and the experimental class to students who take computer networking courses using question instruments. The results of this study are the effectiveness of the developed media and can improve student learning outcomes with an average post-test value of 84.78%. By doing this research, it is hoped that students can be motivated and have a passion for learning in the era of the COVID-19 pandemic