{
"cells": [
{
"cell_type": "markdown",
"metadata": {},
"source": [
"# 5-dimensional Lifshitz spacetimes"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"This worksheet illustrates some features of [SageManifolds](http://sagemanifolds.obspm.fr) (v0.8) on computations regarding Lifshitz spacetimes. \n",
"\n",
"It is based on the following articles:\n",
"- I. Ya. Aref'eva & A. A. Golubtsova,\n",
" [JHEP 2015(04), 011 (2015)](http://link.springer.com/article/10.1007/JHEP04%282015%29011)\n",
"- I. Ya. Aref'eva, A. A. Golubtsova & E. Gourgoulhon, in preparation"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"First we set up the notebook to display mathematical objects using LaTeX formatting:"
]
},
{
"cell_type": "code",
"execution_count": 1,
"metadata": {
"collapsed": true
},
"outputs": [],
"source": [
"%display latex"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"## Spacetime and metric tensor\n",
"\n",
"Let us declare the spacetime $M$ as a 5-dimensional manifold:"
]
},
{
"cell_type": "code",
"execution_count": 2,
"metadata": {
"collapsed": false
},
"outputs": [
{
"name": "stdout",
"output_type": "stream",
"text": [
"5-dimensional manifold 'M'\n"
]
}
],
"source": [
"M = Manifold(5, 'M')\n",
"print M"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"We introduce a first coordinate system on $M$:"
]
},
{
"cell_type": "code",
"execution_count": 3,
"metadata": {
"collapsed": false
},
"outputs": [
{
"data": {
"text/html": [
""
],
"text/plain": [
"chart (M, (t, x, y1, y2, R))"
]
},
"execution_count": 3,
"metadata": {},
"output_type": "execute_result"
}
],
"source": [
"X0. = M.chart('t x y1:y_1 y2:y_2 R:(0,+oo)')\n",
"X0"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"Let us consider the following Lifshitz-symmetric metric, parametrized by some real number $\\nu$:"
]
},
{
"cell_type": "code",
"execution_count": 4,
"metadata": {
"collapsed": false
},
"outputs": [
{
"data": {
"text/html": [
""
],
"text/plain": [
"g = -R^(2*nu) dt*dt + R^(2*nu) dx*dx + R^2 dy1*dy1 + R^2 dy2*dy2 + R^(-2) dR*dR"
]
},
"execution_count": 4,
"metadata": {},
"output_type": "execute_result"
}
],
"source": [
"g = M.lorentz_metric('g')\n",
"var('nu', latex_name=r'\\nu', domain='real')\n",
"g[0,0] = -R^(2*nu)\n",
"g[1,1] = R^(2*nu)\n",
"g[2,2] = R^2\n",
"g[3,3] = R^2\n",
"g[4,4] = 1/R^2\n",
"g.display()"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"A matrix view of the metric components:"
]
},
{
"cell_type": "code",
"execution_count": 5,
"metadata": {
"collapsed": false
},
"outputs": [
{
"data": {
"text/html": [
""
],
"text/plain": [
"[-R^(2*nu) 0 0 0 0]\n",
"[ 0 R^(2*nu) 0 0 0]\n",
"[ 0 0 R^2 0 0]\n",
"[ 0 0 0 R^2 0]\n",
"[ 0 0 0 0 R^(-2)]"
]
},
"execution_count": 5,
"metadata": {},
"output_type": "execute_result"
}
],
"source": [
"g[:]"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"This metric is invariant under the *Lifshitz scaling*\n",
"$$ (t,x,y_1,y_2,R) \\longmapsto \\left(\\lambda^\\nu t, \\lambda^\\nu x, \\lambda y_1, \\lambda y_2, \\frac{R}{\\lambda} \\right)$$\n",
"- If $\\nu=1$ the scaling is isotropic and we recognize the metric \n",
" of $\\mathrm{AdS}_5$ in Poincaré coordinates\n",
"- If $\\nu\\not=1$, the scaling is anisotropic"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"Let us introduce a second coordinate system on $M$:"
]
},
{
"cell_type": "code",
"execution_count": 6,
"metadata": {
"collapsed": false
},
"outputs": [
{
"data": {
"text/html": [
""
],
"text/plain": [
"chart (M, (t, x, y1, y2, r))"
]
},
"execution_count": 6,
"metadata": {},
"output_type": "execute_result"
}
],
"source": [
"X. = M.chart('t x y1:y_1 y2:y_2 r:(0,+oo)')\n",
"X"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"and relate it to the previous one by the transformation $r=\\ln R$:"
]
},
{
"cell_type": "code",
"execution_count": 7,
"metadata": {
"collapsed": false
},
"outputs": [
{
"data": {
"text/html": [
""
],
"text/plain": [
"t = t\n",
"x = x\n",
"y1 = y1\n",
"y2 = y2\n",
"r = log(R)"
]
},
"execution_count": 7,
"metadata": {},
"output_type": "execute_result"
}
],
"source": [
"X0_to_X = X0.transition_map(X, [t, x, y1, y2, ln(R)])\n",
"X0_to_X.display()"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"The inverse coordinate transition is computed by means of the method `inverse()`:"
]
},
{
"cell_type": "code",
"execution_count": 8,
"metadata": {
"collapsed": false
},
"outputs": [
{
"data": {
"text/html": [
""
],
"text/plain": [
"t = t\n",
"x = x\n",
"y1 = y1\n",
"y2 = y2\n",
"R = e^r"
]
},
"execution_count": 8,
"metadata": {},
"output_type": "execute_result"
}
],
"source": [
"X_to_X0 = X0_to_X.inverse()\n",
"X_to_X0.display()"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"At this stage, the manifold's atlas defined by the user is"
]
},
{
"cell_type": "code",
"execution_count": 9,
"metadata": {
"collapsed": false
},
"outputs": [
{
"data": {
"text/html": [
""
],
"text/plain": [
"[chart (M, (t, x, y1, y2, R)), chart (M, (t, x, y1, y2, r))]"
]
},
"execution_count": 9,
"metadata": {},
"output_type": "execute_result"
}
],
"source": [
"M.atlas()"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"and the list of defined vector frames defined is"
]
},
{
"cell_type": "code",
"execution_count": 10,
"metadata": {
"collapsed": false
},
"outputs": [
{
"data": {
"text/html": [
""
],
"text/plain": [
"[coordinate frame (M, (d/dt,d/dx,d/dy1,d/dy2,d/dR)),\n",
" coordinate frame (M, (d/dt,d/dx,d/dy1,d/dy2,d/dr))]"
]
},
"execution_count": 10,
"metadata": {},
"output_type": "execute_result"
}
],
"source": [
"M.frames()"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"The expression of the metric in terms of the new coordinates is"
]
},
{
"cell_type": "code",
"execution_count": 11,
"metadata": {
"collapsed": false
},
"outputs": [
{
"data": {
"text/html": [
""
],
"text/plain": [
"g = -e^(2*nu*r) dt*dt + e^(2*nu*r) dx*dx + e^(2*r) dy1*dy1 + e^(2*r) dy2*dy2 + dr*dr"
]
},
"execution_count": 11,
"metadata": {},
"output_type": "execute_result"
}
],
"source": [
"g.display(X.frame(), X)"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"or, in matrix view:"
]
},
{
"cell_type": "code",
"execution_count": 12,
"metadata": {
"collapsed": false
},
"outputs": [
{
"data": {
"text/html": [
""
],
"text/plain": [
"[-e^(2*nu*r) 0 0 0 0]\n",
"[ 0 e^(2*nu*r) 0 0 0]\n",
"[ 0 0 e^(2*r) 0 0]\n",
"[ 0 0 0 e^(2*r) 0]\n",
"[ 0 0 0 0 1]"
]
},
"execution_count": 12,
"metadata": {},
"output_type": "execute_result"
}
],
"source": [
"g[X.frame(),:,X]"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"To access to a particular component, we have to specify (i) the frame w.r.t. which it is defined and (ii) the coordinates in which the component is expressed:"
]
},
{
"cell_type": "code",
"execution_count": 13,
"metadata": {
"collapsed": false
},
"outputs": [
{
"data": {
"text/html": [
""
],
"text/plain": [
"-e^(2*nu*r)"
]
},
"execution_count": 13,
"metadata": {},
"output_type": "execute_result"
}
],
"source": [
"g[X.frame(),0,0,X]"
]
},
{
"cell_type": "code",
"execution_count": 14,
"metadata": {
"collapsed": false
},
"outputs": [
{
"data": {
"text/html": [
""
],
"text/plain": [
"-R^(2*nu)"
]
},
"execution_count": 14,
"metadata": {},
"output_type": "execute_result"
}
],
"source": [
"g[X.frame(),0,0] # the default chart is used"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"From now on, let us consider the coordinates $X = (t,x,y_1,y_2,r)$ as the default ones on the manifold $M$:"
]
},
{
"cell_type": "code",
"execution_count": 15,
"metadata": {
"collapsed": false
},
"outputs": [],
"source": [
"M.set_default_chart(X)\n",
"M.set_default_frame(X.frame())"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"Then"
]
},
{
"cell_type": "code",
"execution_count": 16,
"metadata": {
"collapsed": false
},
"outputs": [
{
"data": {
"text/html": [
""
],
"text/plain": [
"g = -e^(2*nu*r) dt*dt + e^(2*nu*r) dx*dx + e^(2*r) dy1*dy1 + e^(2*r) dy2*dy2 + dr*dr"
]
},
"execution_count": 16,
"metadata": {},
"output_type": "execute_result"
}
],
"source": [
"g.display()"
]
},
{
"cell_type": "code",
"execution_count": 17,
"metadata": {
"collapsed": false
},
"outputs": [
{
"data": {
"text/html": [
""
],
"text/plain": [
"[-e^(2*nu*r) 0 0 0 0]\n",
"[ 0 e^(2*nu*r) 0 0 0]\n",
"[ 0 0 e^(2*r) 0 0]\n",
"[ 0 0 0 e^(2*r) 0]\n",
"[ 0 0 0 0 1]"
]
},
"execution_count": 17,
"metadata": {},
"output_type": "execute_result"
}
],
"source": [
"g[:]"
]
},
{
"cell_type": "code",
"execution_count": 18,
"metadata": {
"collapsed": false
},
"outputs": [
{
"data": {
"text/html": [
""
],
"text/plain": [
"-e^(2*nu*r)"
]
},
"execution_count": 18,
"metadata": {},
"output_type": "execute_result"
}
],
"source": [
"g[0,0]"
]
},
{
"cell_type": "code",
"execution_count": 19,
"metadata": {
"collapsed": false
},
"outputs": [
{
"data": {
"text/html": [
""
],
"text/plain": [
"g_t,t = -e^(2*nu*r) \n",
"g_x,x = e^(2*nu*r) \n",
"g_y1,y1 = e^(2*r) \n",
"g_y2,y2 = e^(2*r) \n",
"g_r,r = 1 "
]
},
"execution_count": 19,
"metadata": {},
"output_type": "execute_result"
}
],
"source": [
"g.display_comp()"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"## Curvature\n",
"\n",
"The Riemann tensor is"
]
},
{
"cell_type": "code",
"execution_count": 20,
"metadata": {
"collapsed": false
},
"outputs": [
{
"name": "stdout",
"output_type": "stream",
"text": [
"tensor field 'Riem(g)' of type (1,3) on the 5-dimensional manifold 'M'\n"
]
}
],
"source": [
"Riem = g.riemann()\n",
"print Riem"
]
},
{
"cell_type": "code",
"execution_count": 21,
"metadata": {
"collapsed": false
},
"outputs": [
{
"data": {
"text/html": [
""
],
"text/plain": [
"Riem(g)^t_x,t,x = -nu^2*e^(2*nu*r) \n",
"Riem(g)^t_y1,t,y1 = -nu*e^(2*r) \n",
"Riem(g)^t_y2,t,y2 = -nu*e^(2*r) \n",
"Riem(g)^t_r,t,r = -nu^2 \n",
"Riem(g)^x_t,t,x = -nu^2*e^(2*nu*r) \n",
"Riem(g)^x_y1,x,y1 = -nu*e^(2*r) \n",
"Riem(g)^x_y2,x,y2 = -nu*e^(2*r) \n",
"Riem(g)^x_r,x,r = -nu^2 \n",
"Riem(g)^y1_t,t,y1 = -nu*e^(2*nu*r) \n",
"Riem(g)^y1_x,x,y1 = nu*e^(2*nu*r) \n",
"Riem(g)^y1_y2,y1,y2 = -e^(2*r) \n",
"Riem(g)^y1_r,y1,r = -1 \n",
"Riem(g)^y2_t,t,y2 = -nu*e^(2*nu*r) \n",
"Riem(g)^y2_x,x,y2 = nu*e^(2*nu*r) \n",
"Riem(g)^y2_y1,y1,y2 = e^(2*r) \n",
"Riem(g)^y2_r,y2,r = -1 \n",
"Riem(g)^r_t,t,r = -nu^2*e^(2*nu*r) \n",
"Riem(g)^r_x,x,r = nu^2*e^(2*nu*r) \n",
"Riem(g)^r_y1,y1,r = e^(2*r) \n",
"Riem(g)^r_y2,y2,r = e^(2*r) "
]
},
"execution_count": 21,
"metadata": {},
"output_type": "execute_result"
}
],
"source": [
"Riem.display_comp(only_nonredundant=True)"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"The Ricci tensor:"
]
},
{
"cell_type": "code",
"execution_count": 22,
"metadata": {
"collapsed": false
},
"outputs": [
{
"name": "stdout",
"output_type": "stream",
"text": [
"field of symmetric bilinear forms 'Ric(g)' on the 5-dimensional manifold 'M'\n"
]
}
],
"source": [
"Ric = g.ricci()\n",
"print Ric"
]
},
{
"cell_type": "code",
"execution_count": 23,
"metadata": {
"collapsed": false
},
"outputs": [
{
"data": {
"text/html": [
""
],
"text/plain": [
"Ric(g) = 2*(nu^2 + nu)*e^(2*nu*r) dt*dt - 2*(nu^2 + nu)*e^(2*nu*r) dx*dx - 2*(nu + 1)*e^(2*r) dy1*dy1 - 2*(nu + 1)*e^(2*r) dy2*dy2 + (-2*nu^2 - 2) dr*dr"
]
},
"execution_count": 23,
"metadata": {},
"output_type": "execute_result"
}
],
"source": [
"Ric.display()"
]
},
{
"cell_type": "code",
"execution_count": 24,
"metadata": {
"collapsed": false
},
"outputs": [
{
"data": {
"text/html": [
""
],
"text/plain": [
"Ric(g)_t,t = 2*(nu^2 + nu)*e^(2*nu*r) \n",
"Ric(g)_x,x = -2*(nu^2 + nu)*e^(2*nu*r) \n",
"Ric(g)_y1,y1 = -2*(nu + 1)*e^(2*r) \n",
"Ric(g)_y2,y2 = -2*(nu + 1)*e^(2*r) \n",
"Ric(g)_r,r = -2*nu^2 - 2 "
]
},
"execution_count": 24,
"metadata": {},
"output_type": "execute_result"
}
],
"source": [
"Ric.display_comp()"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"The Ricci scalar:"
]
},
{
"cell_type": "code",
"execution_count": 25,
"metadata": {
"collapsed": false
},
"outputs": [
{
"name": "stdout",
"output_type": "stream",
"text": [
"scalar field 'r(g)' on the 5-dimensional manifold 'M'\n"
]
}
],
"source": [
"Rscal = g.ricci_scalar()\n",
"print Rscal"
]
},
{
"cell_type": "code",
"execution_count": 26,
"metadata": {
"collapsed": false
},
"outputs": [
{
"data": {
"text/html": [
""
],
"text/plain": [
"r(g): M --> R\n",
" (t, x, y1, y2, R) |--> -6*nu^2 - 8*nu - 6\n",
" (t, x, y1, y2, r) |--> -6*nu^2 - 8*nu - 6"
]
},
"execution_count": 26,
"metadata": {},
"output_type": "execute_result"
}
],
"source": [
"Rscal.display()"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"We note that the Ricci scalar is constant."
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"## Source model\n",
"Let us consider a model based on the following action, involving a dilaton scalar field $\\phi$ and a Maxwell 2-form $F$:\n",
"\n",
"$$ S = \\int \\left( R(g) + \\Lambda - \\frac{1}{2} \\nabla_m \\phi \\nabla^m \\phi - \\frac{1}{4} e^{\\lambda\\phi} F_{mn} F^{mn} \\right) \\sqrt{-g} \\, \\mathrm{d}^5 x \\qquad\\qquad \\mbox{(1)}$$"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"## The dilaton scalar field\n",
"\n",
"We consider the following ansatz for the dilaton scalar field $\\phi$:\n",
"$$ \\phi = \\frac{1}{\\lambda} \\left( 4 r + \\ln\\mu \\right),$$\n",
"where $\\lambda$ and $\\mu$ are two constants. "
]
},
{
"cell_type": "code",
"execution_count": 27,
"metadata": {
"collapsed": false
},
"outputs": [
{
"data": {
"text/html": [
""
],
"text/plain": [
"phi: M --> R\n",
" (t, x, y1, y2, R) |--> (4*log(R) + log(mu))/lamb\n",
" (t, x, y1, y2, r) |--> (4*r + log(mu))/lamb"
]
},
"execution_count": 27,
"metadata": {},
"output_type": "execute_result"
}
],
"source": [
"var('mu', latex_name=r'\\mu')\n",
"var('lamb', latex_name=r'\\lambda')\n",
"phi = M.scalar_field({X: (4*r + ln(mu))/lamb}, \n",
" name='phi', latex_name=r'\\phi')\n",
"phi.display()"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"The 1-form $\\mathrm{d}\\phi$ is"
]
},
{
"cell_type": "code",
"execution_count": 28,
"metadata": {
"collapsed": false
},
"outputs": [
{
"name": "stdout",
"output_type": "stream",
"text": [
"1-form 'dphi' on the 5-dimensional manifold 'M'\n"
]
}
],
"source": [
"dphi = phi.differential()\n",
"print dphi"
]
},
{
"cell_type": "code",
"execution_count": 29,
"metadata": {
"collapsed": false
},
"outputs": [
{
"data": {
"text/html": [
""
],
"text/plain": [
"dphi = 4/lamb dr"
]
},
"execution_count": 29,
"metadata": {},
"output_type": "execute_result"
}
],
"source": [
"dphi.display()"
]
},
{
"cell_type": "code",
"execution_count": 30,
"metadata": {
"collapsed": false
},
"outputs": [
{
"data": {
"text/html": [
""
],
"text/plain": [
"[0, 0, 0, 0, 4/lamb]"
]
},
"execution_count": 30,
"metadata": {},
"output_type": "execute_result"
}
],
"source": [
"dphi[:] # all the components in the default frame"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"## The 2-form field\n",
"\n",
"We consider the following ansatz for $F$:\n",
"$$ F = \\frac{1}{2} q \\, \\mathrm{d}y_1\\wedge \\mathrm{d}y_2, $$\n",
"where $q$ is a constant. \n",
"\n",
"Let us first get the 1-forms $\\mathrm{d}y_1$ and $\\mathrm{d}y_2$:"
]
},
{
"cell_type": "code",
"execution_count": 31,
"metadata": {
"collapsed": false
},
"outputs": [
{
"data": {
"text/html": [
""
],
"text/plain": [
"coordinate coframe (M, (dt,dx,dy1,dy2,dr))"
]
},
"execution_count": 31,
"metadata": {},
"output_type": "execute_result"
}
],
"source": [
"X.coframe()"
]
},
{
"cell_type": "code",
"execution_count": 32,
"metadata": {
"collapsed": false
},
"outputs": [
{
"name": "stdout",
"output_type": "stream",
"text": [
"1-form 'dy1' on the 5-dimensional manifold 'M'\n",
"1-form 'dy2' on the 5-dimensional manifold 'M'\n"
]
},
{
"data": {
"text/html": [
""
],
"text/plain": [
"(1-form 'dy1' on the 5-dimensional manifold 'M',\n",
" 1-form 'dy2' on the 5-dimensional manifold 'M')"
]
},
"execution_count": 32,
"metadata": {},
"output_type": "execute_result"
}
],
"source": [
"dy1 = X.coframe()[2]\n",
"dy2 = X.coframe()[3]\n",
"print dy1\n",
"print dy2\n",
"dy1, dy2"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"We can then form $F$ according to the above ansatz:"
]
},
{
"cell_type": "code",
"execution_count": 33,
"metadata": {
"collapsed": false
},
"outputs": [
{
"name": "stdout",
"output_type": "stream",
"text": [
"2-form 'F' on the 5-dimensional manifold 'M'\n"
]
},
{
"data": {
"text/html": [
""
],
"text/plain": [
"F = 1/2*q dy1/\\dy2"
]
},
"execution_count": 33,
"metadata": {},
"output_type": "execute_result"
}
],
"source": [
"var('q')\n",
"F = q/2 * dy1.wedge(dy2)\n",
"F.set_name('F')\n",
"print F\n",
"F.display()"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"By construction, the 2-form $F$ is closed (since $q$ is constant):"
]
},
{
"cell_type": "code",
"execution_count": 34,
"metadata": {
"collapsed": false
},
"outputs": [
{
"name": "stdout",
"output_type": "stream",
"text": [
"3-form 'dF' on the 5-dimensional manifold 'M'\n"
]
}
],
"source": [
"print xder(F)"
]
},
{
"cell_type": "code",
"execution_count": 35,
"metadata": {
"collapsed": false
},
"outputs": [
{
"data": {
"text/html": [
""
],
"text/plain": [
"dF = 0"
]
},
"execution_count": 35,
"metadata": {},
"output_type": "execute_result"
}
],
"source": [
"xder(F).display()"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"Let us evaluate the square $F_{mn} F^{mn}$ of $F$:"
]
},
{
"cell_type": "code",
"execution_count": 36,
"metadata": {
"collapsed": false
},
"outputs": [
{
"name": "stdout",
"output_type": "stream",
"text": [
"tensor field of type (2,0) on the 5-dimensional manifold 'M'\n"
]
},
{
"data": {
"text/html": [
""
],
"text/plain": [
"1/2*q*e^(-4*r) d/dy1*d/dy2 - 1/2*q*e^(-4*r) d/dy2*d/dy1"
]
},
"execution_count": 36,
"metadata": {},
"output_type": "execute_result"
}
],
"source": [
"Fu = F.up(g)\n",
"print Fu\n",
"Fu.display()"
]
},
{
"cell_type": "code",
"execution_count": 37,
"metadata": {
"collapsed": false
},
"outputs": [
{
"name": "stdout",
"output_type": "stream",
"text": [
"scalar field on the 5-dimensional manifold 'M'\n"
]
},
{
"data": {
"text/html": [
""
],
"text/plain": [
"M --> R\n",
"(t, x, y1, y2, R) |--> 1/2*q^2/R^4\n",
"(t, x, y1, y2, r) |--> 1/2*q^2*e^(-4*r)"
]
},
"execution_count": 37,
"metadata": {},
"output_type": "execute_result"
}
],
"source": [
"F2 = F['_{mn}']*Fu['^{mn}'] # using LaTeX notations to denote contraction\n",
"print F2\n",
"F2.display()"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"We shall also need the tensor $\\mathcal{F}_{mn} = F_{mp} F_n^{\\ \\, p}$:"
]
},
{
"cell_type": "code",
"execution_count": 38,
"metadata": {
"collapsed": false
},
"outputs": [
{
"name": "stdout",
"output_type": "stream",
"text": [
"tensor field of type (0,2) on the 5-dimensional manifold 'M'\n"
]
},
{
"data": {
"text/html": [
""
],
"text/plain": [
"1/4*q^2*e^(-2*r) dy1*dy1 + 1/4*q^2*e^(-2*r) dy2*dy2"
]
},
"execution_count": 38,
"metadata": {},
"output_type": "execute_result"
}
],
"source": [
"FF = F['_mp'] * F.up(g,1)['^p_n']\n",
"print FF\n",
"FF.display()"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"The tensor field $\\mathcal{F}$ is symmetric:"
]
},
{
"cell_type": "code",
"execution_count": 39,
"metadata": {
"collapsed": false
},
"outputs": [
{
"data": {
"text/html": [
""
],
"text/plain": [
"True"
]
},
"execution_count": 39,
"metadata": {},
"output_type": "execute_result"
}
],
"source": [
"FF == FF.symmetrize()"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"Therefore, from now on, we set"
]
},
{
"cell_type": "code",
"execution_count": 40,
"metadata": {
"collapsed": true
},
"outputs": [],
"source": [
"FF = FF.symmetrize()"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"## Field equations\n",
"\n",
"### Einstein equation\n",
"\n",
"Let us first introduce the cosmological constant:"
]
},
{
"cell_type": "code",
"execution_count": 41,
"metadata": {
"collapsed": false
},
"outputs": [
{
"data": {
"text/html": [
""
],
"text/plain": [
"Lamb"
]
},
"execution_count": 41,
"metadata": {},
"output_type": "execute_result"
}
],
"source": [
"var('Lamb', latex_name=r'\\Lambda')"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"From the action (1), the field equation for the metric $g$ is\n",
"$$\n",
" R_{mn} + \\frac{\\Lambda}{3} \\, g \n",
" - \\frac{1}{2}\\partial_m\\phi \\partial_n\\phi\n",
" -\\frac{1}{2} e^{\\lambda\\phi} F_{mp} F^{\\ \\, p}_n + \n",
" \\frac{1}{12} e^{\\lambda\\phi} F_{rs} F^{rs} \\, g_{mn} = 0 \n",
"$$\n",
"We write it as\n",
"\n",
" EE == 0\n",
"\n",
"with `EE` defined by"
]
},
{
"cell_type": "code",
"execution_count": 42,
"metadata": {
"collapsed": false
},
"outputs": [
{
"name": "stdout",
"output_type": "stream",
"text": [
"field of symmetric bilinear forms 'E' on the 5-dimensional manifold 'M'\n"
]
}
],
"source": [
"EE = Ric + Lamb/3*g - 1/2* (dphi*dphi) - 1/2*exp(lamb*phi)*FF \\\n",
" + 1/12*exp(lamb*phi)*F2*g\n",
"EE.set_name('E')\n",
"print EE"
]
},
{
"cell_type": "code",
"execution_count": 43,
"metadata": {
"collapsed": false
},
"outputs": [
{
"data": {
"text/html": [
""
],
"text/plain": [
"E_t,t = -1/24*(mu*q^2 - 48*nu^2 + 8*Lamb - 48*nu)*e^(2*nu*r) \n",
"E_x,x = 1/24*(mu*q^2 - 48*nu^2 + 8*Lamb - 48*nu)*e^(2*nu*r) \n",
"E_y1,y1 = -1/12*(mu*q^2 - 4*Lamb + 24*nu + 24)*e^(2*r) \n",
"E_y2,y2 = -1/12*(mu*q^2 - 4*Lamb + 24*nu + 24)*e^(2*r) \n",
"E_r,r = 1/24*(lamb^2*mu*q^2 - 48*lamb^2*nu^2 + 8*(Lamb - 6)*lamb^2 - 192)/lamb^2 "
]
},
"execution_count": 43,
"metadata": {},
"output_type": "execute_result"
}
],
"source": [
"EE.display_comp(only_nonredundant=True)"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"We note that `EE==0` leads to only 3 independent equations:"
]
},
{
"cell_type": "code",
"execution_count": 44,
"metadata": {
"collapsed": false
},
"outputs": [
{
"data": {
"text/html": [
""
],
"text/plain": [
"-1/24*mu*q^2 + 2*nu^2 - 1/3*Lamb + 2*nu"
]
},
"execution_count": 44,
"metadata": {},
"output_type": "execute_result"
}
],
"source": [
"eq1 = (EE[0,0]/exp(2*nu*r)).expr()\n",
"eq1"
]
},
{
"cell_type": "code",
"execution_count": 45,
"metadata": {
"collapsed": false
},
"outputs": [
{
"data": {
"text/html": [
""
],
"text/plain": [
"-1/12*mu*q^2 + 1/3*Lamb - 2*nu - 2"
]
},
"execution_count": 45,
"metadata": {},
"output_type": "execute_result"
}
],
"source": [
"eq2 = (EE[2,2]/exp(2*r)).expr()\n",
"eq2"
]
},
{
"cell_type": "code",
"execution_count": 46,
"metadata": {
"collapsed": false
},
"outputs": [
{
"data": {
"text/html": [
""
],
"text/plain": [
"1/24*mu*q^2 - 2*nu^2 + 1/3*Lamb - 8/lamb^2 - 2"
]
},
"execution_count": 46,
"metadata": {},
"output_type": "execute_result"
}
],
"source": [
"eq3 = EE[4,4].expr().expand()\n",
"eq3"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"### Dilaton field equation\n",
"\n",
"First we evaluate $\\nabla_m \\nabla^m \\phi$:"
]
},
{
"cell_type": "code",
"execution_count": 47,
"metadata": {
"collapsed": false
},
"outputs": [
{
"name": "stdout",
"output_type": "stream",
"text": [
"Levi-Civita connection 'nabla_g' associated with the Lorentzian metric 'g' on the 5-dimensional manifold 'M'\n"
]
},
{
"data": {
"text/html": [
""
],
"text/plain": [
"Levi-Civita connection 'nabla_g' associated with the Lorentzian metric 'g' on the 5-dimensional manifold 'M'"
]
},
"execution_count": 47,
"metadata": {},
"output_type": "execute_result"
}
],
"source": [
"nab = g.connection()\n",
"print nab\n",
"nab"
]
},
{
"cell_type": "code",
"execution_count": 48,
"metadata": {
"collapsed": false
},
"outputs": [
{
"name": "stdout",
"output_type": "stream",
"text": [
"scalar field on the 5-dimensional manifold 'M'\n"
]
},
{
"data": {
"text/html": [
""
],
"text/plain": [
"M --> R\n",
"(t, x, y1, y2, R) |--> 8*(nu + 1)/lamb\n",
"(t, x, y1, y2, r) |--> 8*(nu + 1)/lamb"
]
},
"execution_count": 48,
"metadata": {},
"output_type": "execute_result"
}
],
"source": [
"box_phi = nab(nab(phi).up(g)).trace()\n",
"print box_phi\n",
"box_phi.display()"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"From the action (1), the field equation for $\\phi$ is \n",
"$$ \\nabla_m \\nabla^m \\phi = \\frac{\\lambda}{4} e^{\\lambda\\phi} F_{mn} F^{mn}$$\n",
"We write it as\n",
"\n",
" DE == 0\n",
" \n",
"with `DE` defined by"
]
},
{
"cell_type": "code",
"execution_count": 49,
"metadata": {
"collapsed": false
},
"outputs": [
{
"name": "stdout",
"output_type": "stream",
"text": [
"scalar field on the 5-dimensional manifold 'M'\n"
]
}
],
"source": [
"DE = box_phi - lamb/4*exp(lamb*phi) * F2\n",
"print DE"
]
},
{
"cell_type": "code",
"execution_count": 50,
"metadata": {
"collapsed": false
},
"outputs": [
{
"data": {
"text/html": [
""
],
"text/plain": [
"M --> R\n",
"(t, x, y1, y2, R) |--> -1/8*(lamb^2*mu*q^2 - 64*nu - 64)/lamb\n",
"(t, x, y1, y2, r) |--> -1/8*(lamb^2*mu*q^2 - 64*nu - 64)/lamb"
]
},
"execution_count": 50,
"metadata": {},
"output_type": "execute_result"
}
],
"source": [
"DE.display()"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"Hence the dilaton field equation provides a fourth equation:"
]
},
{
"cell_type": "code",
"execution_count": 51,
"metadata": {
"collapsed": false
},
"outputs": [
{
"data": {
"text/html": [
""
],
"text/plain": [
"-1/8*lamb*mu*q^2 + 8*nu/lamb + 8/lamb"
]
},
"execution_count": 51,
"metadata": {},
"output_type": "execute_result"
}
],
"source": [
"eq4 = DE.expr().expand()\n",
"eq4"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"### Maxwell equation\n",
"\n",
"From the action (1), the field equation for $F$ is \n",
"$$ \\nabla_m \\left( e^{\\lambda\\phi} F^{mn} \\right)= 0 $$\n",
"We write it as\n",
"\n",
" ME == 0\n",
" \n",
"with `ME` defined by"
]
},
{
"cell_type": "code",
"execution_count": 52,
"metadata": {
"collapsed": false
},
"outputs": [
{
"name": "stdout",
"output_type": "stream",
"text": [
"vector field on the 5-dimensional manifold 'M'\n"
]
},
{
"data": {
"text/html": [
""
],
"text/plain": [
"0"
]
},
"execution_count": 52,
"metadata": {},
"output_type": "execute_result"
}
],
"source": [
"ME = nab(exp(lamb*phi)*Fu).trace(0,2)\n",
"print ME\n",
"ME.display()"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"We get identically zero; indeed the tensor $\\nabla_p (e^{\\lambda\\phi} F^{mn})$ has a vanishing trace, as we can check:"
]
},
{
"cell_type": "code",
"execution_count": 53,
"metadata": {
"collapsed": false
},
"outputs": [
{
"data": {
"text/html": [
""
],
"text/plain": [
"mu*q d/dy1*d/dy2*dr - 1/2*mu*q*e^(2*r) d/dy1*d/dr*dy2 - mu*q d/dy2*d/dy1*dr + 1/2*mu*q*e^(2*r) d/dy2*d/dr*dy1 + 1/2*mu*q*e^(2*r) d/dr*d/dy1*dy2 - 1/2*mu*q*e^(2*r) d/dr*d/dy2*dy1"
]
},
"execution_count": 53,
"metadata": {},
"output_type": "execute_result"
}
],
"source": [
"nab(exp(lamb*phi)*Fu).display()"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"### Summary\n",
"\n",
"We have 4 equations involving the constants $\\lambda$, $\\mu$, $\\nu$, $q$ and $\\Lambda$:"
]
},
{
"cell_type": "code",
"execution_count": 54,
"metadata": {
"collapsed": false
},
"outputs": [
{
"data": {
"text/html": [
""
],
"text/plain": [
"-1/24*mu*q^2 + 2*nu^2 - 1/3*Lamb + 2*nu == 0"
]
},
"execution_count": 54,
"metadata": {},
"output_type": "execute_result"
}
],
"source": [
"eq1 == 0"
]
},
{
"cell_type": "code",
"execution_count": 55,
"metadata": {
"collapsed": false
},
"outputs": [
{
"data": {
"text/html": [
""
],
"text/plain": [
"-1/12*mu*q^2 + 1/3*Lamb - 2*nu - 2 == 0"
]
},
"execution_count": 55,
"metadata": {},
"output_type": "execute_result"
}
],
"source": [
"eq2 == 0"
]
},
{
"cell_type": "code",
"execution_count": 56,
"metadata": {
"collapsed": false
},
"outputs": [
{
"data": {
"text/html": [
""
],
"text/plain": [
"1/24*mu*q^2 - 2*nu^2 + 1/3*Lamb - 8/lamb^2 - 2 == 0"
]
},
"execution_count": 56,
"metadata": {},
"output_type": "execute_result"
}
],
"source": [
"eq3 == 0"
]
},
{
"cell_type": "code",
"execution_count": 57,
"metadata": {
"collapsed": false
},
"outputs": [
{
"data": {
"text/html": [
""
],
"text/plain": [
"-1/8*lamb*mu*q^2 + 8*nu/lamb + 8/lamb == 0"
]
},
"execution_count": 57,
"metadata": {},
"output_type": "execute_result"
}
],
"source": [
"eq4 == 0"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"## Solution for $\\nu=1$ ($\\mathrm{AdS}_5$)"
]
},
{
"cell_type": "code",
"execution_count": 58,
"metadata": {
"collapsed": true
},
"outputs": [],
"source": [
"eqs = [eq1, eq2, eq3, eq4]\n",
"neqs = [eq.subs(nu=1) for eq in eqs]"
]
},
{
"cell_type": "code",
"execution_count": 59,
"metadata": {
"collapsed": false
},
"outputs": [
{
"data": {
"text/html": [
""
],
"text/plain": [
"[-1/24*mu*q^2 - 1/3*Lamb + 4 == 0,\n",
" -1/12*mu*q^2 + 1/3*Lamb - 4 == 0,\n",
" 1/24*mu*q^2 + 1/3*Lamb - 8/lamb^2 - 4 == 0,\n",
" -1/8*lamb*mu*q^2 + 16/lamb == 0]"
]
},
"execution_count": 59,
"metadata": {},
"output_type": "execute_result"
}
],
"source": [
"[eq == 0 for eq in neqs]"
]
},
{
"cell_type": "code",
"execution_count": 60,
"metadata": {
"collapsed": false
},
"outputs": [
{
"data": {
"text/html": [
""
],
"text/plain": [
"[]"
]
},
"execution_count": 60,
"metadata": {},
"output_type": "execute_result"
}
],
"source": [
"solve([eq == 0 for eq in neqs], lamb, mu, Lamb, q)"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"Hence there is no solution for $\\mathrm{AdS}_5$ with the above ansatz. "
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"## Solution for $\\nu = 2$"
]
},
{
"cell_type": "code",
"execution_count": 61,
"metadata": {
"collapsed": false
},
"outputs": [
{
"data": {
"text/html": [
""
],
"text/plain": [
"[-1/24*mu*q^2 - 1/3*Lamb + 12 == 0,\n",
" -1/12*mu*q^2 + 1/3*Lamb - 6 == 0,\n",
" 1/24*mu*q^2 + 1/3*Lamb - 8/lamb^2 - 10 == 0,\n",
" -1/8*lamb*mu*q^2 + 24/lamb == 0]"
]
},
"execution_count": 61,
"metadata": {},
"output_type": "execute_result"
}
],
"source": [
"neqs = [eq.subs(nu=2) for eq in eqs]\n",
"[eq == 0 for eq in neqs]"
]
},
{
"cell_type": "code",
"execution_count": 62,
"metadata": {
"collapsed": false
},
"outputs": [
{
"data": {
"text/html": [
""
],
"text/plain": [
"[[lamb == 2, mu == 48/r1^2, Lamb == 30, q == r1], [lamb == -2, mu == 48/r2^2, Lamb == 30, q == r2]]"
]
},
"execution_count": 62,
"metadata": {},
"output_type": "execute_result"
}
],
"source": [
"solve([eq == 0 for eq in neqs], lamb, mu, Lamb, q)"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"Hence there are two families of solutions, each famility being parametrized by e.g. $q$. "
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"## Solution for $\\nu = 4$"
]
},
{
"cell_type": "code",
"execution_count": 63,
"metadata": {
"collapsed": false
},
"outputs": [
{
"data": {
"text/html": [
""
],
"text/plain": [
"[-1/24*mu*q^2 - 1/3*Lamb + 40 == 0,\n",
" -1/12*mu*q^2 + 1/3*Lamb - 10 == 0,\n",
" 1/24*mu*q^2 + 1/3*Lamb - 8/lamb^2 - 34 == 0,\n",
" -1/8*lamb*mu*q^2 + 40/lamb == 0]"
]
},
"execution_count": 63,
"metadata": {},
"output_type": "execute_result"
}
],
"source": [
"neqs = [eq.subs(nu=4) for eq in eqs]\n",
"[eq == 0 for eq in neqs]"
]
},
{
"cell_type": "code",
"execution_count": 64,
"metadata": {
"collapsed": false
},
"outputs": [
{
"data": {
"text/html": [
""
],
"text/plain": [
"[[lamb == 2/3*sqrt(3), mu == 240/r3^2, Lamb == 90, q == r3], [lamb == -2/3*sqrt(3), mu == 240/r4^2, Lamb == 90, q == r4]]"
]
},
"execution_count": 64,
"metadata": {},
"output_type": "execute_result"
}
],
"source": [
"solve([eq == 0 for eq in neqs], lamb, mu, Lamb, q)"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"Hence there are two families of solutions, each family being parametrized by e.g. $q$. "
]
},
{
"cell_type": "code",
"execution_count": null,
"metadata": {
"collapsed": true
},
"outputs": [],
"source": []
}
],
"metadata": {
"kernelspec": {
"display_name": "Sage 6.7",
"language": "",
"name": "sage_6_7"
},
"language_info": {
"codemirror_mode": {
"name": "ipython",
"version": 2
},
"file_extension": ".py",
"mimetype": "text/x-python",
"name": "python",
"nbconvert_exporter": "python",
"pygments_lexer": "ipython2",
"version": "2.7.8"
}
},
"nbformat": 4,
"nbformat_minor": 0
}